The patellar locking mechanism involves engagement of which ligament?

The patellar locking mechanism involves engagement of which ligament?

• A. Medial patellar ligament
• B. Lateral patellar ligament
• C. Cranial cruciate ligament
• D. Medial collateral ligament

Answer: (A)

The patellar locking mechanism hinges on the medial patellar ligament. As the leg extends, this ligament slides over the medial trochlear ridge of the femur and becomes engaged, effectively locking the stifle in full extension with little muscular effort. When the leg flexes again, the engagement releases and the joint unlocks. The other ligaments listed have different stabilizing roles in the joint (cranial cruciate limits forward movement of the tibia, medial collateral resists medial stress, and the lateral patellar ligament helps patellar alignment) and do not produce the locking action.