Have you ever noticed your dog skip a few steps on one of its back legs and then, suddenly, be back on all fours like nothing happened? This may be an indication that your dog has Patellar Luxation, which is when the kneecap is moving out of its normal position. Patellar Luxation is an orthopedic condition that is relatively common in dogs, especially in smaller ones such as Chihuahua’s, Yorkshire Terriers, Toy Poodles and Jack Russell Terriers.
What is Patellar Luxation?
To understand what patellar luxation is, one first needs to understand some basic anatomy of a dog’s knee and leg. The two longest bones in the back leg of a dog are the femur(thigh bone/upper leg bone) and the tibia(shinbone/lower leg bone) The knee joint connects these two bones, and in the middle of these two bones, at the front of the knee joint, you will find a little bone which is called the patella(kneecap). The patella is located within a tendon. The patellar tendon sits in a groove and attaches just below the knee to the shinbone, and at the end of the thigh bone. When the kneecap pops out of this groove, this is called a dislocation, also referred to as a luxation. So we speak of patellar luxation when the kneecap moves out of its normal location.
Patellar luxation gets graded on severity, and once the condition progresses, the patella will luxate more frequently and easily, and will start rubbing on the knee joint cartilage. This persistent rubbing will eventually lead to arthritis. Other conditions, such as cranial cruciate ligament rupture, which is when an important ligament in the knee ruptures, can also happen due to the persistent strain from a patella recurrent dislocating. Ligaments are connective tissues that attach bone to bone, and hold structures together and keep them stable.
Symptoms
Depending on the extent of the condition, symptoms may vary. In mild cases, there may be little to no symptoms. A common sign of patellar luxation is intermittent walking on 3 legs, where the dog seems to be skipping a few steps while keeping the affected limb lifted. The dog soon resumes walking normally, often after kicking or shaking the limb. As the condition progresses, the jumping will increase in frequency.
What causes a luxating Patella?
Patellar luxation may happen after trauma to the leg or knee, but can also develop naturally, depending on the build of the dog. General misalignment of the limbs involving the femur, tibia or hip, such as seen in bow-legged dogs, or having a more shallow femoral groove, will lead to abnormal movement. This abnormal movement will increase the risk of developing patellar luxation as it will wear down the inner side of the groove in which the patellar is located. Once this happens, the patella can freely dislocate and slide out of position.
Genetics play a significant role in developing patellar luxation, and there are several dog breeds that have a predisposition to this condition, such as the Chihuahua, Maltese, and the Jack Russell Terrier.
Diagnosis
A veterinarian can perform an exam to diagnose patellar luxation. X-rays may be advised to evaluate the limb for further problems. Patellar luxation can be assigned in a grade from 1 to 4.
Grade 1: The patella can be luxated with manual manipulation but will return to its normal position when released.
Grade 2: The patella luxates with flexion and extension of the knee joint, but returns to its normal position when released. The dog may show some lameness.
Grade 3: The patella luxates with flexion and extension of the knee joint, but can be put back in position manually. Significant lameness exists.
Grade 4: The patella is permanently luxated. The limb is unable to extend and the dog can’t walk on it.
Treatment
Treatment of patellar luxation will depend on the progression of the condition and a dog’s symptoms. Dogs without, or very mild symptoms, and who are only mildly affected(grade 1 & often grade 2) may require only conservative measurements such as:
- Getting to, and maintaining an ideal body weight.
- Use of joint supplements
- Pain management through pain medication
- Exercise adjustment
- Physical rehabilitation
In severe and advanced cases (grade 3 and 4) surgery is advised. For dogs with patellar luxation grade 2, but who show significant clinical signs, surgery may also be advised.
Conclusion
Patellar luxation is an orthopedic problem whereby the kneecap moves out of its normal position. Depending on the severity and progression of the condition, treatment may vary from conservative measurements to surgery.
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