Apparent spontaneous joint restoration in hip osteoarthritis.

Dramatic spontaneous restoration of the joint space in osteoarthritis of the hip is rare, although limited fibrocartilaginous repair is common. Regeneration of the apparent radiographic joint space seems to be associated with peripheral osteophyte formation, but it is difficult to isolate other well-defined factors that promote it. Previous documentation of the phenomenon exists in scattered case reports before the era of widespread total hip replacement. Two recent cases are presented in which patients with bilateral disease had unilateral total hip replacement with simultaneous diminished pain in the contralateral hip accompanied by restoration of the radiographic joint space. Secondary stability, unloading, peripheral osteophyte formation, and other possible factors likely contribute to these unusual natural outcomes of coxarthrosis.