2Cooper C, Campbell L, Byng P, et al. Occupational activity and the risk of hip osteoarthritis. Ann Rheum Dis, 1996, 55: 680-682.
3Hochberg MC, Altman RD, Brandt KD, et al. Guidelines for the medical management of osteoarthritis: part Ⅱ. Osteoarthritis of the knee. American College of Rheumatology. Arthritis Rheum, 1995, 38:1541-1546.