Which muscle should be strengthened in a patient who has an anterior trunk lean during the foot flat (loading response) phase of gait?

• A. Tibialis Anterior
• B. Iliopsoas
• C. Quadriceps
• D. Triceps Surae

Answer: (C)

During loading response, the knee must be controlled eccentrically by the quadriceps to absorb shock and prevent the knee from collapsing into too much flexion. If the quadriceps are weak, the knee tends to drift into excess flexion, and a forward trunk lean often appears as a compensatory strategy to bring the body's center of mass over the stance leg and reduce the external knee flexion moment that the knee extensors would otherwise have to resist. Strengthening the quadriceps directly increases knee extensor strength and the ability to control knee flexion without relying on forward trunk position, restoring a more normal gait pattern. The other muscles listed aren’t the primary drivers of knee control in this phase: the tibialis anterior mainly handles foot clearance and dorsiflexion timing, the iliopsoas is a hip flexor, and the gastrocnemius-soleus complex powers push-off later in stance rather than stabilizing the knee during loading response.