The Science of Osteoarthritis of the Knee
Osteoarthritis involves breakdown of cartilage, changes in underlying bone, and inflammation of the joint lining. It's not just wear and tear but an active process involving the whole joint. Muscle weakness, particularly quadriceps, accelerates progression. Previous injuries such as ACL tears or meniscus tears significantly increase the risk of developing knee osteoarthritis, as these injuries often lead to altered biomechanics and joint instability. Like other degenerative conditions, knee osteoarthritis may coexist with patellofemoral pain syndrome, particularly when both involve similar movement pattern dysfunctions.
Contributing Factors
Knee osteoarthritis isn't simply "wear and tear" but rather the result of abnormal loading patterns that overwhelm your joint's ability to maintain healthy cartilage. The most significant biomechanical factor is quadriceps weakness, which creates a devastating cycle: weak quads fail to adequately absorb impact forces during walking, stairs, and daily activities, placing greater stress on your knee cartilage. As the cartilage breaks down and becomes painful, you naturally become less active, leading to even greater muscle weakness.
Poor movement patterns compound the problem significantly. When your glutes are weak, you lose control of your thigh position, often leading to knee valgus (knee caving inward) during weight-bearing activities. This shifts the loading away from the healthy center of your knee joint to the edges, accelerating cartilage breakdown in these areas. Similarly, tight hip flexors from prolonged sitting alter your walking pattern, reducing knee extension during push-off and creating abnormal shearing forces through the knee.
Previous injuries create lasting biomechanical changes that predispose you to osteoarthritis. An old ACL injury, meniscus tear, or even a significant ankle sprain can subtly alter how you move, creating compensatory patterns that overload your knee joint in ways it wasn't designed to handle. Obesity significantly accelerates this process - not just from the extra weight, but because excess weight often leads to muscle weakness and altered movement patterns that multiply the mechanical stress on your knees during daily activities like stair climbing and getting up from chairs.