Knee arthritis affects a large number of older adults each year. Risk factors are not completely understood. Recent evidence points to loss of hip strength as a possible contributing factor. Foot mechanics such as toeing-in or toeing-out has also been suggested as having an important role in the start of knee osteoarthritis.
Hip abductor muscle weakness changes the alignment of the leg (and knee) when a person is standing upright. The hip abductor muscle moves the leg away from the body. Weakness of the hip abductors causes the pelvis to drop on the contralateral> (other side). This occurs as the contralateral leg swings through when walking.
As the leg swings through, there is a shift in the body’s center of gravity toward the swing contralateral leg. The result is an increased force or load on the medial knee joint of the standing (supportive) leg. Medial refers to the side of the knee closest to the other knee. This idea explains kinetic forces from the top down that contribute to the development of knee degeneration leading to osteoarthritis.
On the other hand, there are equally important forces from the bottom up. And that refers to the foot position and biomechanics of the foot and lower leg acting on the knee. A toe-out position of the foot actually reduces the force of excessive abduction. It turns out that people who turn out may have less risk of knee deterioration compared with people who don’t toe out or who toe out less.