f care for acute low back pain among patients seen by primary care practitioners, chiro- practors, and orthopedic surgeons. N Engl J Med 333:913-7. Cawston T. Billington C, Cleaver C, Elliott S. Hui W. Koshy P, Shingleton B, Rowan A. 1999. The regulation of MMPs and TIMPs in cartilage turnover. Ann N Y Acad Sci 878:12