Patellar Luxation
Patellar luxation occurs when the kneecap (patella) dislocates from its normal position in the femoral groove. It can luxate medially (toward the inside of the leg) or laterally (toward the outside). Medial luxation is far more common, especially in small and toy breeds. The condition is graded from I (intermittent) to IV (permanent dislocation).
Symptoms & Signs
- Intermittent skipping or hopping on the affected leg
- Sudden lameness that resolves quickly
- Bowlegged stance
- Reluctance to jump or exercise
- Cracking or popping sound from the knee
- Chronic lameness in severe grades
Causes & Risk Factors
The primary cause is genetic, involving abnormal development of the femoral groove, tibial crest alignment, or quadriceps muscle group. Trauma can also cause patellar luxation in any breed. Shallow femoral grooves, rotational deformities of the tibia, and malalignment of the quadriceps mechanism all contribute.
Diagnosis
Diagnosis is made through physical examination by manually displacing the patella and grading the severity (Grades I-IV). Radiographs help assess bone alignment and plan surgical correction. Advanced imaging may be needed for complex cases.
Treatment
Grade I typically requires monitoring and weight management. Grades II-IV often benefit from surgical correction including trochleoplasty (deepening the femoral groove), tibial tuberosity transposition, soft tissue reconstruction, or a combination. Post-operative rehabilitation is essential.
Prevention
Selective breeding away from affected individuals is the primary prevention strategy. Maintaining appropriate body weight reduces stress on the joints. Avoiding excessive jumping during growth in predisposed breeds may help.
Prognosis
Excellent prognosis with surgical correction for Grades II-III. Grade IV cases have a more guarded prognosis but can still benefit from surgery. Without treatment, chronic luxation leads to progressive osteoarthritis.
Affected Breeds (38)
| Breed | Species | Size |
|---|---|---|
| Chartreux | Cat | Large |
| Cornish Rex | Cat | Small |
| Devon Rex | Cat | Small |
| Bichon Frise | Dog | Small |
| Boston Terrier | Dog | Small |
| Brittany | Dog | Medium |
| Brussels Griffon | Dog | Toy |
| Bull Terrier | Dog | Medium |
| Bulldog | Dog | Medium |
| Cairn Terrier | Dog | Small |
| Cane Corso | Dog | Giant |
| Cavalier King Charles Spaniel | Dog | Small |
| Chihuahua | Dog | Small |
| Chinese Crested | Dog | Toy |
| Chow Chow | Dog | Medium |
| Cocker Spaniel | Dog | Medium |
| Dachshund | Dog | Medium |
| French Bulldog | Dog | Small |
| Great Pyrenees | Dog | Giant |
| Havanese | Dog | Small |
| Italian Greyhound | Dog | Toy |
| Jack Russell Terrier | Dog | Small |
| Kai Ken | Dog | Medium |
| Keeshond | Dog | Medium |
| Lagotto Romagnolo | Dog | Medium |
| Lhasa Apso | Dog | Small |
| Maltese | Dog | Small |
| Papillon | Dog | Toy |
| Pharaoh Hound | Dog | Medium |
| Pomeranian | Dog | Small |
| Pug | Dog | Small |
| Scottish Terrier | Dog | Small |
| Shiba Inu | Dog | Medium |
| Shih Tzu | Dog | Small |
| Shikoku | Dog | Medium |
| Tibetan Terrier | Dog | Medium |
| West Highland White Terrier | Dog | Small |
| Yorkshire Terrier | Dog | Small |