Grade III medial patellar luxation: surgical technique
2-year-old Pomeranian, 3 kg, with right hind limb lameness that has gone from intermittent to continuous. The right patella is almost always luxated medially; you can reduce it manually but it reluxates as soon as you let go. The tibial tuberosity is deviated medially.
What is the most appropriate plan?
chevron_right Show answer and explanation
A. It is grade I: conservative management, since the patella can be reduced manually
In grade I the patella sits in place and only luxates when pushed, returning to the trochlea by itself. A patella that is almost permanently luxated and reluxates when released is grade III.
B. Lateral capsular imbrication alone, which is sufficient in most cases
Soft-tissue techniques alone do not correct quadriceps malalignment or a shallow trochlea, and have a high reluxation rate.
C. It is grade III: surgery combining trochlear deepening (wedge or block recession), lateral tibial tuberosity transposition and lateral imbrication/medial release
Correct. Tuberosity transposition realigns the extensor mechanism; wedge or block recession deepens the trochlea while preserving cartilage; the soft tissues balance the tensions. The combination reduces reluxation.
D. Abrasion trochleoplasty of the cartilage, preferable because it is quicker
Abrasion removes the hyaline cartilage and replaces it with fibrocartilage, with more osteoarthritis. Wedge or block recessions preserve cartilage and are preferable in adults.
lightbulb Key takeaway
Grades: I, luxatable but reduces spontaneously; II, luxates spontaneously and stays luxated until reduced; III, permanently luxated but reducible; IV, luxated and irreducible, often with bony deformity. Operate according to lameness, not grade alone; grade IV may require correction of femoral or tibial deformity.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.