This report describes stifle luxation resultant from multiple ligamentous injuries in a spur-thighed tortoise (Testudo graeca). Despite an absence of obvious trauma in the case history, the tortoise presented with acute, unilateral hind limb lameness. Diagnosis of stifle luxation was based on cranial drawer motion, increased rotational joint instability, and radiographic findings. Joint stabilization was accomplished by a combination of cranial cruciate reconstruction using an autograft of lateral vastus muscle in an over-the-top procedure and lateral imbrication of the joint capsule. Postoperative management included restriction of limb movement for 6 wk and parenteral chondroprotective regime. Treatment was effective in restoring clinically normal function to the limb.