Patellar luxation may result from malformation of the femoral trochela, poor alignment between the distal femur and the proximal tibia or rotation of the proximal extremity of the tibia. This abnormality results in the patellar straight ligament being out of line with the trochlear groove. Lateral luxation of the patellar is occasionally seen in large dogs with valgus deformity (2). In cat patellar luxation is a very rare event and bilateral luxation of that is much more rare (3).
5 months old, male DSH cat was referred to the Small animal Clinic of University of Tehran, which had a history of lameness of both hind limbs. The prior history was unknown but after clinical examination abnormality in both stifles was highly suspected, it also had a painful stifle joint on deep palpation of pattelars. In clinical examination; the patella will often spontaneously relocate when the problem resolves immediately. Then radiography was taken on craniocaudal, mediolateral, and skyline views of both stifles and these radiographs revealed: Medial patellar luxation was more in the left stifle than the right one. Left and right stifle showed grade four patellar luxation according to Anderson's classification (1). Developmental medial patellar luxation is associated with other anatomical abnormalities of the medial bowing of the proximal tibia and medial rotation of the tibia tuberosity. After final diagnosis the case was referred to surgical treatment.
1. Collinson. R. (1994): Manual of small animal arthrology. The stifle. Edited by G. Anderson. BSAVA. pp: 275-277.
2. Donald E. Thrall, Text book of veterinary diagnostic radiology. 4rd. Ed. W.B. Saunders Company. Philadelphia, pp: 189-191.
3. Houlton, J.E. F and Meynink S.E. (1989): Medial patella luxation in the cat. Journal of small animal practice, 30, 349-352.
4. Kevin Kealy J. (2000): Diagnostic radiology of the dog and cat. 2rd. ed. W.B. Saunders Company. Philadelphia, pp: 363.