Characterization of rapidly progressive osteoarthritis of the hip in its early stage.

Disease progression of RPOH during 12 months after the onset of hip pain could be classified into two distinct types based on the absence (type 1) and presence (type 2) of femoral head destruction in association with MMP-3 and pelvic tilt as biological and mechanical factors, respectively. MMP-3 may be helpful to differentiate these two types in the early stage of RPOH.