Articular cartilage is the highly specialized connective tissue of diarthrodial joints. Its main function is to provide a smooth, lubricated surface for articulation and to facilitate the transmission of loads with a low frictional coefficient. The articular cartilage does not have blood vessels, lymphatics, and nerves. Articular cartilage is quite susceptible to injury and has a limited capacity for intrinsic healing and repair. Protecting the health of the articular cartilage is quite important for joint health. Its unique and complex structure makes treatment and repair or restoration of the defects challenging for the patient, the surgeon, and the physical therapist.