why do my knee joints hurt
Some of the most common reasons for knee pain are sprained ligaments, meniscus (cartilage) tears, tendonitis, and runner's knee. But the knee is a complex joint, and there's plenty more that can go wrong. In this condition, the kneecap slides out of position, causing knee pain and swelling. 2  Patellofemoral pain syndrome. 3  This condition often results from issues associated with muscle imbalance, tightness, and alignment of the legs, rather than an injury.