Patellar luxation is the displacement of the patella (knee cap) out of the trochlear groove of the femur. In other words, it is the movement of the patella to either side of the groove in which it lies. The cause of medial patellar luxation (MPL) is unclear. MPL can be traumatic or congenital/developmental. Toy and miniature breeds are twelve times more likely to develop MPL than large breeds so a genetic predisposition seems likely. Affected dogs usually present under 6 months of age or young adults, with no history of trauma. MPL is often bilateral. Developmental MPL is viewed as an anatomic anomaly of the entire pelvic limb.
These changes result in bow leggedness which causes a displacement of the quadriceps muscle group to the
quadriceps muscle group to the inside of the thigh. Affected dogs are young with open growth plates so the muscular forces ‘pull’ the area to which the tendon is attached on the shin (the tibial tuberosity) to the inside (medially). Because the skeleton is still so malleable this change becomes a self-perpetuating problem. Usually, the earlier the problem can be corrected (under 12 months of age), the better the result.
MPLs are graded from I to IV, with I being the least severe. Grade I is treated conservatively with main medication and exercise. Grade II can be treated conservatively or surgically and is a cause for much controversy in veterinary science. Surgery is recommended for grades III and IV.
Physical rehabilitation alone has not been shown to correct or prevent MPL but it is a matter of time before research publications are available in this regard. At the very least rehabilitation will assist with strengthening and pain management or as a form of pre-habilitation should surgery become an option.
General management is vitally important in these patients. Manage weight, advise joint supplements and exercise appropriately. Avoid quick turns and reduce exposure to slippery surfaces. The main goals of conservative management of MPL are:
- Pain management.
- Strengthening of gluteal muscles and quadriceps group. Exercises could include stairs, sit-to-stands and downhill walking (to engage the quads). Any form of sensory input (wraps or kinesiotape) applied during exercise sessions may improve muscle activation.
- Maintain/enhance core stability. Diagonal leg stands and exercising on unstable surfaces encourages engagement of abdominal and paraspinal muscle groups.
- Manage the compensatory patterns found in soft tissues. The sartorius and iliopsoas muscles may be shortened and require stretching. Many of these dogs shift weight forward and may present with trigger points around the shoulders and in the triceps muscle. Regular massage can be very effective in releasing these areas of discomfort.
There is much that can be done, over and above surgery, to improve the quality of life of dogs with patellar luxation.