Stifle
Cranial cruciate ligament rupture
Medial meniscus injury
Caudal Cruciate ligament rupture
Collateral ligament damage
Deranged stifle joint
Patella luxation
Medial patella luxation
Lateral patella luxation
Osteochondritis dissecans - Lateral femoral condyle
Long digital extensor tendon avulsion/tear
Trauma/Fractures
Cranial Cruciate Ligament Rupture
Signalment
Breeds – Any breed, but Labrador retrievers, Rottweilers, Bernese Mountain dogs, St. Bernards, and other large and giant breeds seem to be particularly affected. Cruciate ligament rupture occurs in small breed dogs, but dogs should be carefully evaluated for concurrent patella luxation.
Gender – Spayed females may be predisposed
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Age – Middle-aged to older dogs (4 to 8 years of age) are more commonly affected.
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Etiology - While acute rupture of the cranial cruciate ligament may occur as a result of trauma, nearly all cases of cranial cruciate ligament rupture (CCLR) occur as a result of a slow degenerative process of the fibers of the ligament. Loss of CCL support invariably leads to progressive OA. Rupture of the cranial cruciate ligament results in gross instability of the stifle. Alternatively, the ligament may sustain a partial rupture, causing less obvious instability and lameness. In both cases, degenerative joint changes are initiated at the time of the rupture, and progress with time. Joint instability invariably leads to progressive OA with deterioration of limb function. Based on recent studies, there may be a genetic component to CCLR in some breeds. Bilateral cruciate ligament disease is quite common.
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History
Dogs may have a progressive pelvic limb lameness or a sudden nonweightbearing lameness. The lameness may improve gradually over the first few weeks, and then worsen again. Alternatively, the ligament may sustain a partial rupture, causing less obvious instability and lameness. Dogs have reduced activity, difficulty negotiating stairs, and may not sit squarely and symmetrically.
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Clinical Findings
Dogs typically have lameness, ranging from barely perceptible to nonweight-bearing lame. The joint is assessed for swelling by palpating medial and lateral to the patellar ligament. Normally, the edges of the ligament can be distinctly felt, but with joint effusion, the patellar ligament is less distinct and fluid may be palpable. The femoral condyles and trochlear ridges are palpated for osteophytes or joint capsule thickening. Thickening of the medial aspect of the distal femur is often present in dogs with chronic rupture of the cranial cruciate ligament (medial buttress). The stifle is flexed and extended to evaluate for crepitus, clicking, or snapping, which might indicate osteoarthritis or a damaged meniscus. Dogs with complete or partial cranial cruciate ligament rupture often have marked pain with full stifle extension.
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The most common method of assessing for cranial cruciate ligament rupture is the cranial drawer test. One index finger is placed on the tibial tuberosity and the soft tissues are stretched caudally with the thumb until the head of the fibula is reached. The other index finger is placed on the patella and the soft tissues are stretched with the thumb until the lateral fabella is palpated. Now place the stifle in mild flexion and try to move the tibia cranially and caudally. The examiner should avoid internally rotating the limb while performing the drawer maneuver. Drawer motion should be assessed through a range of motion. In some cases of partial cranial cruciate ligament rupture there may be some drawer motion in flexion but not extension. Sedation may be necessary in some tense patients.
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An indirect method of evaluating the cranial cruciate ligament is the tibial compression test. The stifle is flexed to a standing angle. One hand is placed on the stifle with the forefinger resting on the tibial tuberosity. The tarsus is slowly flexed with the other hand, while keeping the stifle at a fixed angle. This causes tension in the gastrocnemius muscle and common calcaneal tendon which compresses the femur and tibia. In the absence of the cranial cruciate ligament, cranial movement of the tibial tuberosity in relation to the distal femur is detected.
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Diagnostics
Cranial cruciate ligament rupture is a diagnosis by physical examination. MRI may be performed in cases of partial rupture of the cruciate ligament, but this is expensive and there is generally a high index of suspicion based on physical exam. Radiographs are typically made to assess the degree of osteoarthritis that may be present. Osteophytes may be seen on the distal pole of the patella, on the tibia near the insertion of the cranial cruciate ligament, the medial and lateral epicondyles, and the fabella. Effusion of the stifle joint is nearly always present as assessed by evaluating a lateral radiograph for compression of the fat pad in the cranial portion of the joint, and bulging of the joint capsule in the caudal portion of the joint. If an extracapsular procedure is being considered, evaluation for the presence and position of the fabella is performed. When considering biomechanical-altering procedures such as tibial plateau leveling osteotomy or tibial tuberosity transposition, the tibial plateau angle are measured from a lateral view. Finally, the joint should be evaluated for neoplasia. Approximately 1 in 200 patients with lameness localized to the stifle joint may have neoplasia, including osteosarcoma of the distal femur or proximal tibia, or histiocytic sarcoma involving the joint itself.
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Treatment Options
Surgical stabilization is recommended for a successful outcome. Inadequate surgical and postoperative treatment may result in joint stiffness, muscle atrophy, lameness, and poor function. Proper surgical intervention and the appropriate use of physical rehabilitation techniques in combination with pharmaceutical agents are necessary to achieve an optimal outcome.
In some cases, such as the concurrent presence of terminal disease such as neoplasia, or severe organ dysfunction that would endanger the patient's life with anesthesia, conservative treatment may be opted. It is important to realize that satisfactory function will occur in about 20% of dogs. In small dogs (less than 15 kg), conservative therapy may suffice if surgery is not an option, although surgical treatment is still the preferred route to reduce the atrophic and degenerative changes that invariably occur with conservative treatment. In larger dogs, some form of stifle stabilization is nearly always advocated to prevent or minimize the progression of OA.
To date, over 50 different techniques have been devised to treat CCLR. These techniques range from simple forms of extracapsular stabilization using wire or suture material, to sophisticated arthroscopic prosthetic ligament replacement. In addition to the stabilization procedure, it is important to debride loose and torn ligament remnants and to inspect and debride damaged portions of the menisci, especially the caudal horn of the medial meniscus, which is frequently damaged in dogs with CCLR. The method of joint exploration may have an effect on early postoperative recovery. An arthrotomy carries significant morbidity, while arthroscopic evaluation and joint debridement, although more difficult and time consuming, results in less pain and swelling, and earlier return to limb use.
Extracapsular stabilization
In this form of stabilization, nylon suture or stainless steel suture material is used to provide extracapsular (outside the joint capsule) support, mimicking the support provided by the intact CCL. Most commonly, the suture is passed around the lateral (and sometimes a separate suture around the medial) fabella (sesamoid bone located in the origin of the gastrocnemius muscle) and through a tunnel drilled into the proximal tibial tuberosity. This procedure minimizes cranial drawer and provides immediate stabilization of the stifle, allowing early rehabilitation to be initiated. At some point, the prosthetic material may fatigue and break. However, the periarticular fibrosis that develops over 8 to 10 weeks provides the ultimate stabilization of the stifle. Nevertheless, it is common for some degree of cranial drawer motion to be present weeks to months after surgery. Rehabilitation after surgery seems to reduce the amount of postoperative drawer motion and may result in a more stable joint.
Another form of extracapsular stabilization is the tightrope procedure. With this procedure, bone tunnels are drilled to mimic the isometric points of the cruciate ligament on the lateral side during joint flexion and extension. Fiber tape is used with a toggle rod and button to stabilize the stifle. The advantage of this technique over traditional extracapsular techniques is that the fiber tape maintains tension throughout a range of motion because the tape is placed in a more isometric position. The procedure has tested well in biomechanical tests and early clinical results are good. The repair provides immediate stability to the stifle joint, but over time, some drawer motion may return.
Physical rehabilitation starts the day of surgery with cryotherapy, NSAIDs, and gentle passive range of motion (PROM). Controlled leash walks are started within 24 hours and active use of the limb is encouraged. Treadmill walking may be useful to encourage weight-bearing, and aquatic therapy may be started approximately one week post-operatively if the incision is sealed and there is no opening of the wound edges or drainage or discharge from the incision. PROM is continued with an emphasis on regaining preoperative levels of stifle joint extension by 10 days after surgery. Rear limb strengthening can be facilitated by stair climbing, uphill walking, or pulling a cart. Jumping up on the hind limbs is prevented for the first 10 to 12 weeks to prevent damage to the repair.
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Tibial Plateau Leveling Osteotomy (TPLO)
This procedure uses a completely different concept to provide stability to the stifle joint. The main concept behind the previously described procedures is to limit cranial drawer motion by physically restraining the tibia from shifting cranially in relation to the femur during weight-bearing or nonweight-bearing activities. The TPLO is based on the principle that cranial tibial thrust during weight-bearing is prevented using a combination of altered biomechanical forces and active muscle contraction acting on the stifle during weight-bearing to stabilize the joint. Clinical experience and a growing number of studies have shown that this procedure gives the most consistent and best results regarding clinical function and slowing the progression of osteoarthritis.
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The principles of this procedure are most easily understood if one considers that in the normal stifle, the weight-bearing surface of the tibial plateau slopes caudally. With CCLR, the femoral condyle is not restrained by the CCL and the femoral condyles roll down this slope during weight-bearing, resulting in a net cranial displacement of the tibia in relation to the femur. This overall concept is similar to performing a tibial compression test, in which forces and muscle tension acting on the stifle result in cranial displacement of the tibia in the CCL-deficient stifle. With the TPLO, an osteotomy of the proximal tibia is performed, allowing the tibial plateau to be rotated to nearly level position. The osteotomy is then stabilized using screws and a specially designed bone plate. This reduces the shear forces acting at the articular surfaces of the femur and tibia, resulting in more compressive forces and eliminating the cranial tibial thrust during weight-bearing. The periarticular muscles provide additional stability to the stifle during weight-bearing.
Cryotherapy, NSAIDs, and PROM exercises, along with limited activity in the form of progressively longer leash walks, are provided in the initial postoperative period. As healing of the osteotomy site progresses, a gradually increasing protocol of limb use is prescribed. It is important to realize that in addition to healing joint capsule and altering stresses on the cartilage and bone of the joint, that the osteotomy has adequate time to heal to prevent complications related to bone healing and implant failure. In this regard, aquatic therapy may be particularly useful to reduce weight-bearing forces.
The postoperative complications associated with this procedure are primarily related to the altered biomechanics of the stifle. In particular, patellar ligament desmitis is very common during the first month. Clinically, patients may demonstrate more lameness during the postoperative period than is normally expected if patient activity is not adequately restricted. The patella ligament is wider, and there is pain on palpation of the ligament, especially at its insertion to the tibial crest. Also associated with the altered biomechanical stresses placed on the joint, is the occurrence of avulsion of a portion of the tibial crest in some patients. Postoperative rehabilitation protocols must consider these possible complications. Fortunately, the problems are usually self-limiting as tissue remodeling and healing progress. Preventive strategies, centered on preventing excessive stresses of the patellar ligament on the tibial crest, may be useful in the early postoperative period. Specifically, preventing excessive flexion of the stifle while weight-bearing should reduce the tensile forces at the ligament insertion point. Preventing jumping, running, stair climbing, and walking while crouching should help to keep the quadriceps muscle-patellar ligament unit in a relatively shortened position, reducing the tensile forces on the tibial crest and patellar ligament. If patellar ligament desmitis occurs despite these preventive measures, treatment in the form of severely restricting exercise, cryotherapy, and NSAIDs, should help to resolve the problem before becoming more serious. A more gradual increase in activity level should be instituted after the tissues have healed adequately to resume activity.
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CORA-Based Leveling Osteotomy (CBLO)
The concept behind this procedure is similar to the TPLO, but the tibial osteotomy is further distally away from the joint is the circular cut is directed in the opposite direction. A special compression screw along with a specialized bone plate and screws secure the position of the bones after rotation. Although some have described advantages of this technique over TPLO, there is insufficient evidence to suggest better clinical outcomes than those achieved with TPLO at this time. One advantage of the CBLO is in dogs with open growth plates because the level of the osteotomy avoids the growth plate.
Tibial Tuberosity Advancement (TTA)
This procedure is similar in principle to the TPLO, but it accomplishes the goal of providing dynamic stability to the stifle joint by advancing the tibial tuberosity as opposed to rotating the tibial plateau. The end result is that contraction of the quadriceps muscle causes compression of the joint rather than shearing forces that result in cranial tibial thrust.
The procedure is performed by performing an osteotomy of the tibial tuberosity. The tuberosity is advanced to a point that eliminates cranial tibial thrust. The osteotomy is held in place with a specially designed plate and cage or material in the shape of a wedge which maintains the proper amount of advancement. Bone graft is used to fill the defect created by the advancement.
Postoperatively, it is important to allow healing of the osteotomy, which generally takes 4 to 8 weeks. During that time, control of pain and inflammation are important. In addition, excessive activity is avoided to allow proper healing.
Proponents of the technique indicate that surgery time is shorter than the TPLO and the procedure is less invasive, potentially resulting in a lowered incidence of postoperative infections. In addition, there is generally no or little patella ligament desmitis, and because there is no increased tension of the quadriceps mechanism, there is no patella or tibial crest fracture, and patella-femoral chondromalacia is minimal. Compared to the TPLO, resorts suggest that the incidence of post-operative meniscal tears is greater with TTA.
Intracapsular stabilization methods
These procedures have fallen out of favor, but use fascial strips, a portion of the patellar ligament, or prosthetic materials placed in an intraarticular fashion via arthrotomy or arthroscopy to mimic the anatomic path of the original CCL and allow more normal stifle joint kinematics. Most procedures using a graft leave one end of the graft attached to the tibial crest and have the free end of the tissue pass through the stifle joint, going caudally and proximally through the joint capsule, and then are secured to the lateral femoral condyle. Other procedures have the free end of the graft pass under the intermeniscal ligament prior to traversing caudally and proximally through the joint. If the placement is not isometric, stretching and tearing of the implant may occur. In addition, biological tissues undergo a prolonged period of weakness until the tissue revascularizes and gains additional strength. This process may take months, and the tissue may not regain sufficient strength to function in the same fashion as a normal CCL. To combat this process, some surgeons also use an extracapsular fabella-tibial suture to augment the repair and reduce the stress on the graft. To date, prosthetic material used in veterinary medicine has been universally unsuccessful in providing permanent stability to the stifle. Invariably, the material degenerates, often resulting in chronic intra-articular inflammation.
Postoperative physical rehabilitation includes reducing pain and the inflammatory response through the use of NSAIDs and cryotherapy. Depending on the material used, the rehabilitation efforts must follow changes in tissue strength. For example, in cases with an autograft or allograft of fascia, rehabilitation efforts must conform to changes in the strength of the implant over a period of time. In particular, autografts and allografts are generally strong when initially put in place, but when put under tension, they stretch. Also, the tissue becomes much weaker over the next 2 to 20 weeks while revascularization and incorporation occur. If graft incorporation is augmented with an extracapsular suture, a rehabilitation program similar to that for extracapsular repair may be initiated, although attention to controlling inflammation is particularly important to prevent a hostile environment for the graft. Ultimate tissue strength is only achieved following bio-integration of the graft.
Medial meniscus injury
Signalment
Breeds – Any breed, but Labrador retrievers, Rottweilers, Bernese Mountain dogs, St. Bernards, and other large and giant breeds seem to be particularly affected. Nearly always related to cranial cruciate ligament rupture.
Gender – Spayed females may be predisposed because of the association with cruciate ligament disease.
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Age – Middle-aged to older dogs (4 to 8 years of age) are more commonly affected.
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Etiology - Isolated meniscal injuries in the absence of CCLR are rare in dogs. Mensical damage is nearly always related to partial or complete rupture of the CCL, and the caudal aspect of the medial meniscus is most commonly affected. The reason that this region is preferentially damaged is related to the anatomic attachment of the medial meniscus to the proximal tibia. When the femur is displaced caudally in relation to the tibia during weight-bearing, the femoral condyle creates abnormal compressive and shearing forces on the meniscus, eventually causing gross damage to the tissue. Postoperative meniscal tears occur relatively commonly following surgery for a cranial cruciate ligament rupture, even if a partial meniscectomy has already been performed. The lateral meniscus can be damaged, but it is less common.
History
It is rare to have an isolated meniscal tear in the absence of cruciate ligament injury. Therefore, the patient generally has clinical signs related to cruciate ligament rupture. In cases that have already had surgery for cruciate ligament disease, dogs with postoperative meniscal tears may initially do well, then have a sudden onset of lameness some weeks to months after surgery. Owners sometimes state that they can hear a clicking or snapping sound when the dog walks.
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Clinical Findings
Clinical signs are generally related to cruciate ligament rupture, with lameness being the major finding. When placing the stifle through a complete range of motion, a meniscal click may be felt or even heard. The click may only occur one time, or it may be repeatable as the stifle is continuously put through a range of motion. The click is usually appreciated more with full flexion, then extension.
Care must be taken to make certain the sensation is not crepitus associated with osteoarthritis. Osteoarthritis crepitus is usually more continuous in nature, whereas meniscal click has a single, more staccato type sensation.
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Diagnostics
The presence of a meniscal click has a high probably of an actual damaged meniscus. Palpation of the caudomedial joint compartment may be painful, especially during flexion and extension while internally rotating the stifle. MRI and ultrasonography have also been used to diagnose meniscal tears. Most cases are confirmed with arthroscopy or arthrotomy.
Treatment Options
Approximately 20-50% of the patients that are presented with CCLR have concurrent medial meniscal damage. Meniscal damage is most commonly treated with either arthrotomy or arthroscopic debridement of the damaged portion. Cases with damage to the entire meniscus are treated with a complete meniscectomy, but whenever possible, it is preferable to remove only the damaged portion with a partial meniscectomy. It is also possible that even if the meniscus is normal at the time of stifle stabilization for a CCLR, that the medial meniscus will become damaged at some time in the future. In fact, this probably occurs more commonly than is reported, and may explain why some dogs do well initially, and then perform poorly several months to years after surgery. In these situations, if a clicking of the stifle is palpated or heard during joint manipulation or walking, joint exploration is recommended. Removal of the damaged meniscus often results in significant improvement. Several reports have identified damage to the lateral meniscus in association with CCLR during careful arthroscopic examination. Following partial menisectomy and stifle stabilization, NSAIDs, cryotherapy, and controlled ROM are indicated followed by progressive leash walks starting the day after surgery.
Caudal Cruciate ligament rupture
Signalment
Breeds – No breed predilection
Gender – No gender predilection
Age – No age predilection
Etiology - Isolated injury to the caudal cruciate ligament is rare. It occurs more commonly in combination with other traumatic injuries of the stifle, as part of a deranged stifle joint.
History
Dogs generally have a history of trauma that results in severe damage to the stifle if multiple structures are involved. In cases or isolated caudal cruciate ligament injury, there may be a sudden onset of mild lameness which is difficult to diagnose.
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Clinical Findings
Isolated caudal cruciate ligament tear is a difficult diagnosis by physical examination, especially since cranial cruciate ligament disease is so common. The same hand and finger positions are used as for assessing the cranial cruciate ligament. However, instead of cranial drawer motion, there is caudal drawer. Caution must be used to asses the "resting" position of the tibia and femur because dogs may have the tibia in cranial drawer, and the examiner simply reduces the tibia back into the normal position; this is not true caudal drawer, but rather reduction of the stifle joint. True caudal drawer is assessed with the stifle in the normal anatomical position, and then moving the tibia caudally relative to the femur. Injury to other stifle tissues (deranged stifle) generally results in severe instability of the stifle.
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Diagnostics
In most cases of isolated caudal cruciate ligament damage, the lesion is discovered on exploration of the stifle to assess for meniscal or cranial cruciate ligament injury. This may be performed arthroscopically or through an arthrotomy. Radiographs are generally not diagnostic unless there is an avulsion fragment. MRI may be diagnostic, and an experienced sonographer may be able to evaluate the ligament with ultrasound.
Treatment Options
The treatment of caudal cruciate ligament injuries is controversial, even in human orthopedics. Because most dogs with caudal cruciate ligament ruptures also have other injuries of the stifle, repair of each individual condition is addressed. In cases of isolated caudal cruciate injury, the diagnosis should be confirmed to be certain that the lameness is not actually due to a cranial cruciate ligament rupture or other condition such as a meniscal tear. If the lameness is minimal, conservative treatment may be pursued in less active dogs. If a sporting or working dog is affected, surgery may be performed. The most common technique is an extracapsular patella-fibular suture with a small hole drilled in the head of the fibula and a patella-tibial suture with a small hole drilled in the caudomedial proximal tibia, followed by rest and physical rehabilitation.
Collateral ligament damage
Signalment
Breeds – No breed predilection
Gender – No gender predilection
Age – No age predilection
Etiology - Isolated injury to the medial or lateral collateral ligament is rare, but injury to the medial collateral ligament is more common than the lateral collateral ligament. It occurs more commonly in combination with other traumatic injuries of the stifle, as part of a deranged stifle joint. Injury to the medial collateral ligament almost always is associated with cranial cruciate ligament injury, so this structure should also be carefully evaluated.
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History
Dogs generally have a history of trauma that results in severe damage to the stifle if multiple structures are involved. In cases or isolated collateral ligament injury, there may be a sudden onset of lameness.
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Clinical Findings
Dogs generally have lameness proportional to the severity of the injury. It is important to fully extend the stifle joint to increase the tension in the collateral ligament that would normally occur. A valgus stress is applied to open the medial joint if the medial collateral ligament is affected, and a varus stress is applied to open the lateral joint if the lateral collateral ligament is affected.
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Diagnostics
Varus and valgus stress views with the stifle joint extended are diagnostic. Ultrasound or MRI may also be of use diagnostically.
Treatment Options
Grade 1 and 2 sprains may be treated conservatively with rest and bandage support. If gross instability exists, surgery is necessary. If the ligament is not shredded, suture repair should be performed, using appropriate suture patterns. It is usually necessary to follow this with prosthetic collateral ligament repair with tissue anchors or screws and washers in the origin and insertion of the medial collateral ligament or a hole drilled in the head of the fibula for the lateral collateral ligament with suture material. The sutures should be tied with the stifle in extension. The repair is protected during healing with a bandage and restricted activity.
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Deranged stifle joint
Signalment
Breeds – No breed predilection
Gender – No gender predilection
Age – No age predilection
Etiology - Trauma is involved in creating damage to multiple structures of the stifle, including any combination of cranial and caudal cruciate ligaments, medial and lateral collateral ligaments, and medial and lateral menisci.
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History
Cases of deranged stifles have severe trauma, such as being hit by a car, getting the pelvic limb caught in a fence, or an attack from another animal.
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Clinical Findings
There is a great deal of instability in the stifle, including cranial and caudal drawer, excessive varus and valgus motion, and meniscal click depending on the structures involved. There is a non weight-bearing lameness and moderate to severe swelling of the stifle
Diagnostics
Most injuries are appreciated on physical examination. Radiographs should be made to be certain there are no fractures to complicate matters. MRI and ultrasound evaluations may give more specific information, but most injuries are evaluated during surgical exploration.
Treatment Options
Deranged stifles are among the most challenging conditions to repair because multiple structures are involved. Smaller dogs and cats may be treated with a transarticular pin, placed from the tibia into the stifle. The entrance into the stifle should be at the insertion point of the cranial cruciate ligament. It should pass in the intercondylar space of the femur avoiding weight-bearing articular surfaces, enter the femur near the origin of the cranial cruciate ligament, and be firmly seated in the femur. The pin is maintained for 4 weeks, at which time it is removed. Pin breakage is relatively common. Attention is paid to regaining range of motion and reducing lameness during the rehabilitation period. joint is thoroughly evaluated
Larger dogs or working or service dogs should have the injuries repaired separately if possible. The joint is thoroughly examined before surgery to determine which structures are damaged. Exploration of the joint is performed during surgery. Any remaining portions of the cruciate ligaments are debrided. Loose or torn menisci are removed and the arthrotomy is closed. The first step in the repair is to treat collateral ligament damage. If the ligament(s) is (are) not shredded, it may be sutured with one or two locking loop sutures. Most of the time, the ligament(s) is (are) severely damaged and a prosthetic collateral repair is undertaken with screws and washers or tissue anchors in the medial and lateral femur for repair of the medial and lateral collateral ligaments. The medial collateral ligament is repaired with similar implants placed in the tibia with the suture stabilizing the medial collateral ligament, while the suture is placed in a small hole drilled in the fibula or passed around the head of the fibula to repair the lateral collateral ligament. It is important to be certain that the stifle joint is reduced with no cranial or caudal drawer before tightening the sutures. If both collateral ligaments are involved, it is important to go back and forth between the medial and lateral sutures and tighten them in alternating fashion so that one side is not overtightened relative to the other. Next, the cranial and caudal cruciate ligaments are stabilized using extracapsular suture techniques. A suture is passed around the lateral labella and through a hole drilled in the proximal tibial tuberosity. Another suture is passed around or through a hole drilled in the head of the fibula and circumferentially around the patella. With the stifle reduced so that there is no cranial or caudal drawer, and held in a functional standing angle, the sutures are tightened in alternating fashion so that one suture does not pull the stifle in drawer relative to the other.
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Patella luxation
Medial patella luxation
Lateral patella luxation
Signalment
Breeds – May be any breed, but small breeds are predisposed.
Gender – No apparent gender predisposition.
Age – Most patella luxations are considered to be congenital in origin, with the bony structural issues present in puppies. However, the condition may become more prominent as the patient ages.
Etiology - Although patella luxations may be traumatic in origin, they are most commonly related to abnormalities in hind limb conformation, especially a medially displaced tibial tuberosity. 75-80% of patella luxations are medial. If a lateral patella luxation is present, it is most likely in a large breed or chondrodystrophic breed of dog. However, medial patella luxation is more common, even in larger breeds. On occasion, the patella may luxate in both directions.
History
Dogs often have a history of skipping leg lameness, in which the patella luxates, the dog holds the limb in the air for a couple steps, the patella reduces spontaneously with muscle contraction, and the dog is seemingly normal. As the condition progresses, the lameness becomes more consistent. Dogs also have a history of not jumping up on furniture or into vehicles, or difficulty negotiating stairs. Dogs with Grade 4 or ectopic patellas as young puppies may walk in a crouched posture because the alignment malformations are so great that the quadriceps mechanism is actually functioning as a stifle flexor rather than extensor. It is important to initiate treatment as soon as possible in these cases to prevent permanent joint contracture. Dogs that develop rupture of the cranial cruciate ligament have a sudden nonweight-bearing lameness.
Clinical Findings
Dogs may have an intermittent skipping type lameness or a more consistent lameness. Often, the alignment issues may be seen with the animal in a square standing position, or with the dog lying on on its back with the pelvic limbs pulled out in a straight, OFA-like position.
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Diagnostics
Patella luxation is a diagnosis by palpation. In some cases, sedation is helpful to achieve muscle relaxation Patella luxations are classified from grade 1 to grade 4, with 4 being the most severely affected. The classifications are based on the degree of clinical signs, ease of patellar luxation and reduction, and severity of bony abnormalities. Concurrent cranial cruciate ligament rupture is present in 15 to 20% of middle aged and older dogs with chronic patella luxation.
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The first step is to locate the patella to avoid the error of reducing a luxated patella back into the trochlear groove and erroneously thinking that the patella is luxating in the wrong direction. The tibial tuberosity is first located. Then the patella ligament is followed proximally to the patella. If the patella is in the reduced position, there will be similar amounts of medial and lateral femoral condyles on either side and the trochlear groove is not palpated. If the patella is luxated, there will be no femoral condyle on the side where the patella is luxated, and the trochlear groove may be palpated, although it may be relatively shallow.
Medial luxations are more common than lateral luxations in all dog breeds and in cats. To assess for a medial patella luxation, the stifle is extended, the tibia is internally rotated (to accentuate the misalignment of the quadriceps mechanism), and the patella is pushed in a medial direction. Patella luxation should be checked in a variety of stifle angles; most of the time, it is easier to luxate the patella with the stifle extended, but on occasion some flexion of the joint makes luxation easier.
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To assess for a lateral patella luxation, the stifle is extended, the tibia is externally rotated (to accentuate the misalignment of the quadriceps mechanism), and the patella is pushed in a lateral direction. Patella luxation should be checked in a variety of stifle angles; most of the time, it is easier to luxate the patella with the stifle extended, but on occasion some flexion of the joint makes luxation easier.
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Patella luxations may be graded based on the severity of the luxation and misalignment. Grade 1 luxations are intermittent, with no or occasional lameness. The patella is in the trochlear groove, but can be luxated during exam; the patella spontaneously reduces when the pressure is released. Grade 2 patella luxations have more consistent lameness. The patella may be in the trochlear groove or luxated at the time of exam. Flexion and extension of the limb with simultaneous internal or external rotation of the stifle results in luxation and reduction. The patella is easy to luxate manually. Grade 3 patella luxations are recognized by having a patella that is luxated at all times, but it can be manually reduced; it re-luxates when pressure is released. The degree of limb malalignment is greater that with grades 1 and 2 luxations. Grade 4 patella luxations are recognized by having a patella that is luxated all of the time, and it cannot be reduced. Limb alignment abnormalities are severe, and it may be impossible to fully extend the stifle joint. The trochlear groove may be smooth. In addition, the dog usually carries the limb if only one limb is affected, or may walk in a crouched position if both limbs are affected.
Treatment Options
Surgery is indicated when gait abnormalities or lameness are present. Surgical correction of patella luxations usually requires reconstruction of both soft tissues and bone to realign the quadriceps mechanism. In almost all cases the tibial crest is transposed and pinned. A technique to deepen the trochlear groove (trochleoplasty) is also used in cases with a shallow trochlear groove. A trochlear groove prosthesis is available for cases that have severe erosion of the articular cartilage. A capsulectomy or imbrication of the soft tissues on the redundant side is also performed. Large dogs may have varus deformity of the distal tibia. In these cases, it is often beneficial to perform a distal femoral osteotomy to align the trochlear groove with the axis of the tibia.
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The typical medial patella luxation repair in a small dog begins with a skin incision on the craniomedial aspect of the stifle (this makes the scar less obvious). The subcutaneous tissues are elevated to allow access to the craniolateral stifle. A stab incision is made in the large joint space between the femoral condyle and tibial plateau The lateral arthrotomy is extended from just proximal to the tibia to proximal to the patella. The patella is luxated medially if it is not already luxated. The trochlear groove is evaluated for depth. It should be at least as deep as half the thickness of the patella. If it is not, a groove deepening procedure is performed, such as a trochlear wedge sulcoplasty or a block recession trochleoplasty. These techniques preserve the articular cartilage of the trochlear groove and are preferable to simply rasping a deeper groove and removing the cartilage. The wedge or block of bone is then replaced. At this point, the patella is reduced and should be must more stable. Next, the tibial tuberosity is transposed to a more lateral position to realign the quadriceps mechanism. After performing the osteotomy of the tibial tuberosity, it is allowed to "float" to its realigned neutral position. A medial release of the joint capsule may be necessary in grade 3 or 4 patella luxations. It moved slightly more laterally and then pinned in place. A pin and tension band is recommended in larger dogs. The patella should remain in the groove with flexion and extension of the stifle. A capsulectomy of the lateral joint capsule is performed to "tighten" the redundant tissue. Routine closure is performed.
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After surgery the tissues must be allowed to heal before vigorous rehabilitation begins, particularly if the tibial crest was transposed. During the first few weeks, cryotherapy and NSAIDs may be used for inflammation. Active use of the limb is encouraged, but initial activity should be limited to short leash walks and jumping is not allowed. Passive ROM is beneficial for joint resurfacing and cartilage healing, especially if a trochleoplasty was performed. Small breed dogs in particular are sometimes reluctant to bear weight on the affected limb, even in the absence of apparent pain or complications. In these cases, weight shifting activities or swimming may be instituted to encourage limb use. After several weeks, strengthening exercises may be initiated. Motion should be limited to the sagittal plane to avoid undue stress on the repair. Therefore, activities that involve turning or pivoting, such as figure of eights and weaving through vertical poles, are avoided. The prognosis is generally fair to good for grades 2 and 3, but guarded for grade 4 luxations.
Osteochondritis dissecans - Medial aspect of the lateral femoral condyle
Signalment
Breeds – Large and giant breed dogs
Gender – Males are predisposed, but females also affected
Age – Generally noted from 4 to 9 months of age
Etiology - Abnormal endochondral ossification of the deep layers of articular cartilage results in focal areas of thickened cartilage that are prone to injury. In the absence of excessive stress, the lesion may heal. However, further stress on the cartilage may result in a cartilage flap. This condition is termed osteochondritis dissecans (OCD).
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History
Mild to moderate lameness, decreased activity
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Clinical Findings
Mild to moderate lameness, atrophy of the pelvic limb muscles, pain may be elicited with hyperextension of the stifle, there is effusion of the stifle joint. Other than trauma, effusion of the stifle joint in a skeletally immature dog is most likely to be OCD of the stifle.
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Diagnostics
Generally diagnosis suspected on signalment and orthopedic exam and confirmed with an AP radiograph of the stifle. Caution should be exercised in overinterpreting the radiographs because the fossa of the origin of the ling digital extensor tendon is sometimes mistaken for an OCD lesion. CT evaluation is very helpful in diagnosing OCD also.
Treatment Options
Removal of cartilage flap with an arthrotomy or arthroscopy, curettage of subchondral bone, change diet to a large breed growth diet, nonsterodal anti-inflammatory medication, rehabilitation. If the lesion is large enough, a cartilage transfer procedure may be performed, using the nonarticular cartilage from the lateral trochlear ridge as a donor site.
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Long digital extensor tendon avulsion/tear
Signalment
Breeds – Medium to large dogs, especially Greyhounds or Great Danes
Gender – No gender predilection
Age – Usually skeletally immature dogs, but can affect mature dogs
Etiology - May be related to trauma, with avulsion fracture at the origin of the long digital extensor tendon.
History
Dogs may have a history of some type trauma, sometimes related to explosive activity.
Clinical Findings
Dogs have mild to moderate pelvic limb lameness. There is usually pain and swelling of the cranial aspect of the lateral femoral condyle.
Diagnostics
Radiographs of the stifle may indicate an avulsion fracture of the origin of the long digital extensor tendon. With time, the fragment may hypertrophy. Ultrasound examination of the region may reveal damage to the tendon at its origin.
Treatment Options
If the avulsion fracture fragment is large enough, it may be secured with a screw or 2 small pins. If the fragment is too small for repair, or if the tendon is torn, the small fragments are excised and the tendon may be sutured to the cranial tibial muscle fascia.
Trauma/Fractures
Signalment
Breeds – Any breed
Gender – No gender predilection
Age – Any age, although skeletally immature dogs are prone to fractures of the lateral aspect of the humeral condyle.
Etiology – Trauma. Many cases occur as a result of jumping down from a distance or landing awkwardly. Other cases occur as a result of automobile trauma. Fractures or the patella, femoral conduces, or bicondylar fractures may occur. If the fracture is a result of severe trauma, careful evaluation of the thoracic and abdominal structures is important to detect trauma to these areas.
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History
Often owners witness trauma, such as a fall, hit by automobile, or other sudden traumatic event that results in sudden onset of severe lameness.
Clinical Findings
Fractures of the femoral condyles or patella result in pain on manipulation and crepitation during manipulation of the stifle. Palpable anatomical differences are usually apparent. Dogs are usually non weight-bearing lame.
Diagnostics
Radiographs are generally diagnostic, but careful evaluation should be made to distinguish fractures of the lateral or medial aspects of the femoral condyle from bicondylar (Y or T) fractures of the distal femur. Patella fractures are generally seen on radiographs. CT evaluation may give additional details.
Treatment Options
Fractures of the femoral condyles require internal fixation to restore anatomy and function and are generally repaired with a transcondylar screw placed in lag fashion with additional fixation of either an antirotational pin or K screw, or a bone plate and screws.
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Bicondylar (T or Y) fractures of the femur are more serious. In some cases, an osteotomy of the tibial tuberosity may be necessary to gain better access to the femoral condyles for reduction and fixation. This requires fixation of the osteotomy with a pin and tension band after the main repair is performed. A transcondylar screw is placed in lag fashion after the articular surface is anatomically reduced. The medial aspect of the condyle is attached to the mainshaft of the femur with a bone plate and screws. The lateral aspect of the condyle is attached to the mainshaft of the femur with either an intramedullary pin or bone plate and screws.
Fractures of the patella are often multiple and/or too small for fixation. If this occurs, removal of the fragments is usually performed. If the fragment is large enough, a pin and tension band or screw placed in lag fashion are used to repair the fracture. Postoperatively, it is best to keep the stifle in an extended position for 2-3 weeks, to reduce tension on the repair.
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