We describe a large family, including 54 affected individuals, with multiple epiphyseal dysplasia (MED) with involvement of the peripheral joints only. In this family, a mutation in the COL9A2 gene was detected. Every affected person has involvement of the knee joints. Other involved joints are the elbow, ankle, wrist, hand, and feet joints. Involvement of the shoulder or hip joints is never seen after adolescence. The height of the affected individuals is short to normal; spinal involvement is never seen. The penetrance of the gene is complete. However, the expression of the gene is highly variable.