Why is there a high risk of hip subluxation/dislocation in high lumbar L1-L2?

• A. Unopposed flexion and adduction push the femoral head superiorly and posteriorly
• B. Excessive knee extension
• C. Excessive ankle plantarflexion
• D. Weak neck muscles

Answer: (A)

Hip stability around the joint depends on a balance of forces from different muscle groups. When a lesion is high in the lumbar spine, the hip flexors and adductors tend to be relatively unopposed because the abductors and extensors are weakened. This creates flexion and adduction contractures at the hip. Those unopposed forces pull the femoral head upward and toward the back against the acetabular rim, so the head is displaced superiorly and posteriorly. Over time, this abnormal position increases the risk of the femoral head subluxing or dislocating. The other options don’t directly disrupt hip alignment in this way—knee extension or ankle plantarflexion don’t by themselves destabilize the hip, and neck muscle weakness is unrelated to hip stability.