Chrondromalacia causes knee tenderness, knee pain in front of the knee, and a grating sensation in the knee. The knee pain is worst after sitting for a prolonged period of time or when getting out of a chair. The knee cartilage is affected probably from overuse, trauma and/or abnormal forces on the knee, such as a misaligned patella. Chondromalacia is treated with rest or immobilization and nonsteroidal anti-inflammatory drugs for pain. Physical therapy, especially quadriceps strengthening and hamstring stretching may also be helpful. Surgery is beneficial if there is a problem with the alignment of the patella that cannot be corrected with therapy.