The knee joint is lined by cartilage over the bones on the lower end of the thigh bone, and upper end of the leg bone and behind the knee cap. Due to injury, or aging, the cartilage gets frayed, and damaged, and may cause pain, and swelling in the knee with or without clicking or popping.
Patients who have persistent pain, and swelling, which is not improved with medications, cortisone injection, and physical therapy, or if such damage is found in arthroscopic surgeries when done for other reasons, like meniscus injury or ligament repair, may need attention. The loose cartilage is cleaned and debrided to stable margins. This procedure, of removing the damaged flaps of the cartilage, as well as cleaning up is called chondroplasty.