Articular cartilage is a versatile structure that provides a near fric-tionless surface while resisting compression and shear forces and distributing stress. Damage to the joint surface of the knee may result in both short- and long-term disability. Arthroscopy and magnetic resonance imaging allow better identification of injuries to the hyaline cartilage and subchondral bone. Chondral and osteochondral fractures, loss of the menisci, and recurrent instability appear to contribute to the deterioration of the knee joint surfaces. Prevention of this deterioration is critical since there are no reliable methods available at the present time to restore the articular cartilage of the knee. Correction of the mechanical axis and elimination of pathologic laxity are fundamental issues that must be recognized and addressed. Treatment of chronic chondral injuries with arthroscopic debridement and abrasion arthroplasty provide somewhat unpredictable and incomplete, symptomatic relief in selected patients. Auto-geneic and allogeneic tissue as well as synthetic materials have been used to repair the articular surface with the hope of decreasing friction and preventing progressive erosion. Osteochondral allograft transplantation has achieved limited early success with the associated inherent risk of disease transmission. Periosteal resurfacing and carbon fiber implantation are promising experimental techniques that require further research and development. Prosthetic arthroplasty is a reproducible, end-stage reconstructive procedure that cannot be applied to a young, athletic population.