At some point, stair climbing will involve alternate hip flexion and knee flexion of both lower extremities. In order to initiate the hip flexion required to advance a limb up a stair or an incline, the hip flexors (iliopsoas) have to be strong. Having now placed the foot on the stair above, the referenced limb is now in a position of hip flexion and knee flexion (while the contralateral limb behind is straight in weight bearing/stabilizing mode). To advance the contralateral limb would require the activation of the hip extensors (Gluteus maximus) and knee extensors (quadriceps) of the referenced, flexed limb in order to straighten it and provide the lift necessary to advance the contralateral limb. Therefore, stair ascension would be difficult, if not impossible, without strong gluteal muscles or strong quadriceps.
Quadriceps gait describes an abnormal gait that occurs as a result of weak quadriceps. Quadriceps weakness can result from a peripheral nerve lesion (femoral nerve), spinal nerve root lesion, trauma or disease (muscular dystrophy). To prevent buckling of the knee or excessive flexion of the knee during stance, particularly midstance, the patient compensates by maintaining the knee in extension during stance by bending forward at the waist and/or pushing back on the front of the thigh with the hand. The forward bend/lean at the hip shifts the line of gravity anterior to the medial-lateral axis of the knee, thereby mechanically locking the knee in extension which reduces the need for activation of the quadriceps muscle (see Video 1 below). [1]
The gluteus maximus gait results from weakness of the gluteus maximus and is characterized by a posterior thrusting of the trunk at initial contact in an attempt to maintain hip extension of the stance leg and prevent the trunk from moving forward. Leaning the trunk posteriorly during the stance phase shifts the body’s line of gravity posterior to the hip, reducing the demands of the hip extensor muscles (see Video 2 below). [1]
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