A patient with cerebral palsy is scheduled for a psoas lengthening procedure. This intervention will MOST significantly improve which phase of the gait cycle?

• A. Initial swing
• B. Terminal stance
• C. Midstance
• D. Pre-swing

Answer: (B)

Lengthening the iliopsoas, a primary hip flexor, reduces a tight hip flexor’s resistance to hip extension. In late stance (terminal stance), the leg must extend as the body prepares for push-off and forward progression. When the hip can fully extend, propulsion is more effective and the limb advances more efficiently. In cerebral palsy, hip flexor tightness often limits this extension, so releasing the psoas directly improves forward progression during terminal stance.

Other phases rely less on hip extension. Initial swing requires hip flexion to bring the leg forward, and shortening or weakening the hip flexor would not enhance that motion. Pre-swing and midstance depend more on ankle plantarflexors, knee mechanics, and overall stability than on achieving hip extension, so the biggest gain comes from improving terminal stance through psoas lengthening.