What condition involves abnormal development of the pelvic joint causing the head of the femur and the acetabulum not to be aligned properly, often with a 'bunny hop' gait?

• A. Tuber coxae fracture
• B. Hip dysplasia
• C. SI malposition
• D. Lumbarization

Answer: (B)

Hip dysplasia is a developmental problem where the hip joint doesn’t form or fit together correctly—the femoral head and the acetabulum are not aligned or congruent. This leads to joint laxity and often subluxation, so the hip becomes unstable. With this instability, the animal often displays a bunny-hop gait, where the hind limbs move together rather than stepping independently, because the hip joint cannot provide stable, smooth rotation. The other options describe different pelvic or spinal issues that don’t involve this developmental misalignment of the hip joint itself: a tuber coxae fracture is an acute pelvic injury, SI malposition involves the sacroiliac joint, and lumbarization is a vertebral anomaly. Hip dysplasia best fits the described abnormal hip development and characteristic gait.