12/31/2025
Hip weakness, especially in the gluteus medius and external rotators, drives a kinematic chain collapse that causes excessive foot pronation, knee valgus (knees touching), and medial knee pain.
The chain reaction from hip to foot
Weak hip abductors fail to control pelvic drop and femoral internal rotation during single-leg stance (like walking), so the femur drifts inward, dragging the tibia into valgus and the foot into overpronation.
This "collapsing kinetic chain" loads the medial knee (patellofemoral joint, MCL) and flattens the arch, explaining why patients show knees-together posture even sitting or rising.
Why glutes are key stabilizers
Glute medius eccentrically controls hip adduction/internal rotation under ground reaction forces; when weak, Trendelenburg gait emerges with contralateral pelvic drop, tibial internal rotation, and foot collapse.
External rotators (like piriformis, gemelli) also resist femoral internal rotation; their weakness amplifies valgus moments and increases injury risk like ACL tears or MTSS.
Clinical signs and patient example
Severe pronation with "knees touching" at rest/movement indicates hip-driven dynamic valgus, not just local foot weakness—fixing arches alone fails without hip retraining.
Test: glute squeeze shifts the arch supinates and realigns the chain; no change means poor activation.
Treatment: hip-first strengthening
Progress clamshells/bridges only if felt in glutes (not knee/back); add side planks, single-leg stance, monster walks, and step-downs for functional control.
Studies show 4–8 weeks of hip abductor/external rotator work reduces valgus by 43%, improves arch height, and cuts medial knee pain.