Runner's knee, also known as patellofemoral pain syndrome, is a common condition that causes pain around the kneecap. It often occurs in athletes, particularly runners, due to repetitive stress on the knee joint. Factors such as improper footwear, overuse, or muscle imbalances can contribute to this condition. Symptoms typically include a dull ache in the front of the knee, especially during activities like running, climbing stairs, or sitting for long periods. Treatment often involves rest, ice, physical therapy, and strengthening exercises to improve knee stability and reduce pain.