Why does knee pain occur when walking down stairs?

When you go down stairs, your knee bends more and works harder to control your movement. This action increases the pressure on the patellofemoral joint—the part where your kneecap meets your thigh bone. In people with knee osteoarthritis, the cartilage may be worn thin, which means the smooth cushion that helps the bones glide over each other is damaged. This loss of cushioning leads to more friction and pain. Additionally, conditions like chondromalacia patella occur when the cartilage on the underside of the kneecap softens or wears away, making movement even more painful during stair descent. The extra force during each step forces the joint to absorb more impact and can exacerbate symptoms. Studies studying the biomechanics of stair descent show that increased knee flexion and joint loading contribute largely to the discomfort. Understanding these factors can help guide exercises and treatments to ease the pain and improve joint motion.