Disability due to joint pain is increasing as our society ages. This pain often results from cartilage degeneration in joints due to osteoarthritis or trauma. Cartilage damage from sports injuries is common and the normal repair response results in the formation of fibrous tissue that is inferior to normal cartilage in structure and function and eventually degenerates with time. As a result, tens of thousands of total knee replacements and other surgical procedures are performed each year to repair cartilage defects in the knee. A common clinical treatment for cartilage lesions is debridement of the damaged tissue followed by drilling into the subchondral bone to stimulate tissue regeneration. Although this procedure often provides pain relief, it does not restore long-term function and frequently hastens additional degeneration of the injured site. Alternative procedures for repair or regeneration of human articular cartilage are needed.