Pronation is synonymous to the foot “unlocking” and is necessary to accommodate to uneven surfaces, dissipate impact forces, and allow your big toe to reach the ground. Excessive foot pronation can cause the lower leg to rotate too far inward, which may increase twisting forces at the ankle and knee.
Reduced foot pronation means your foot does not “unlock” and thereby does not reduce the “shock wave” of force traveling from your foot upward resulting in increased stress to the body.
Genu Valgum refers to the inward collapse of the knee during the stance phase. This is a typical motion when running and is mechanically coupled with foot pronation and hip adduction (inward collapse). It is also coupled with hip and knee internal rotation. Too much inward collapse results in increased stress to the knee joint, the patella (knee cap), and lower leg.
A typical gait pattern but one that can lead to an increase in forces on the hip and knee joints if the hip muscles are not strong enough.
Trendelenburg gait occurs from weakness in the hip musculature of the stance leg. With each step during gait, you spend time standing on one leg, which is called “single support”. During single support, the pelvis, opposite to the stance limb, drops slightly. Excessive pelvic drop is associated with excessive hip and knee inward collapse to the opposite side of the body and can create increased shearing forces within the pelvis, hip, and low back.