A dog presents with craniocaudal movement of the stifle. What is the most likely diagnosis?

• A. CCL rupture
• B. Patellar luxation
• C. Hip dysplasia
• D. OCD

Answer: (A)

The key concept is joint stability of the stifle and how a torn cranial cruciate ligament presents. When the cranial cruciate ligament is intact, the tibia is held from moving forward relative to the femur as the joint bears weight. If this ligament ruptures, the tibia can translate cranially relative to the femur during loading, producing a movement of the entire stifle in the cranial direction known as the cranial tibial thrust or a cranial drawer sign. This craniocaudal movement is classic for a cranial cruciate ligament rupture in dogs and explains the observed lameness and instability.

Patellar luxation involves abnormal tracking of the kneecap rather than translation of the tibia within the stifle. Hip dysplasia affects the hip joint and presents with signs related to the hip rather than cranial translation of the stifle. OCD refers to cartilage lesions that cause joint pain and effusion, not a specific stifle translation sign.