Medial Patellar Luxation

Bichon Frise

Who is usually affected?
-Toy and small breed dogs are most commonly affected
-Larger dogs and cats may also be affected
-Problems are usually first detected in younger to middle-aged animals

What is happening?
-Due to anatomical problems, the kneecap (patella) is intermittently or permanently displaced (luxated) toward the inside of the leg, outside of the groove in which it should track
-Abnormal knee (stifle) mechanics cause an awkward gait, joint inflammation, and cartilage wear
-Arthritis and pain progress over time

Clinical signs you might notice in your pet
-Stiffness or limping in a hind leg after exercise or rest
-Intermittent limping during walking or running
-Limping becomes consistent as time passes

X-ray appearance of a normally positioned patella Click to enlarge

-Sitting with a hind leg held off to the side
-Crouched posture in the rear

Diagnosis
-Orthopedic examination to determine the joint(s) affected and to identify abnormal patellar movement
-X-rays to evaluate the stifle region for its anatomy, swelling, and arthritis

Surgical treatment
-A variety of techniques may be used alone or in combination depending on the patient's anatomy and degree of luxation, recommended surgical options may include:
- Trochleoplasty -used to deepen the groove in which the patella should track
- Tibial tuberosity transposition -used to realign the powerful muscles (quadriceps muscles) that control patellar motion by moving their point of attachment on the front of the tibia

X-ray appearance of medial patellar luxation Click to enlarge

- Lateral capsular imbrication -used to tighten the joint capsule on the outside of the stifle, creating a force that pulls the patella toward the outside of the joint
- Medical capsular release -used to loosen the joint capsule on the inside surface of the stifle, releasing a force that pulls the patella toward the inside of the joint (often used to complement lateral imbrication)
- Rectus muscle transfer -used to realign the portion of the quadriceps muscle group that naturally pulls the patella toward the inside of the stifle

Special postoperative care
-Patient activity is strictly limited until adequate initial healing occurs (expect 4-6 weeks) followed by gradually increasing activity over another 4-6 weeks
-X-rays may be taken at specific intervals to evaluate healing
-Physical therapy may be prescribed

Expected results after surgery
-Much improved comfort and function in the stifle
-Ultimate results will depend on the amount of arthritis existing prior to surgery and/or the severity of the patellar luxation