58 patients underwent treatment for Slipped Upper Femoral Epiphysis (SUFE) at our unit from 1984 to 2001. 4 (7%) patients had bilateral SUFE at the time of primary admission, 17 (29%) patients were diagnosed with a slip of the contralateral hip at review during adolescence. The remaining 37 patients whose contralateral hips were not operated upon at completion of growth were reviewed at an average follow-up of 8 years (range 2–17) after the primary admission. 13 patients were not available for review, so 24 patients were examined and their hips radiographed.

Iowa hip score was used to assess the function of the hips, Antero-posterior and lateral radiographic views were taken to look for evidence of epiphyseal slip and degenerative joint disease. The Calcar Femorale was used as a radiographic landmark to check for a slip. Ahlback’s score was used to grade osteoarthritis.

4 out of 24 patients at the follow-up examination showed displacement of the contralateral femoral head that was greater than 3 standard deviation and was consistent with previously unrecognised physiolysis. 4 contralateral hips showed evidence of butteressing at the site of physeal reminence but the displacement was less than 3 standard deviations and so they were not considered to have slipped. 3 of these hips with buttressing had evidence of Grade I osteoarthritis. Overall incidence of bilateral SUFE in our study, excluding the 13 patients who were not available for follow-up was 25 out of 45 (55%).

This real existence of unrecognised contralateral slip, the increased risk of OA in these hips and significant rate of bilaterality, stresses the need to readdress the current mode of management of the contralateral hips in patients treated for unilateral SUFE.