Understanding pelvic mobility is important to correctly diagnose and treat painful hips with positive impingement test in non-arthritic patients.

Introduction: To determine repeatability of pelvic mobility, calculated as both change in sacral slope (∆SS) and pelvic tilt (∆PT), and evaluate their correlations with pelvic incidence (PI) in non-arthritic patients with hip pain and positive impingement test.

Methods: The cohort comprised 82 patients aged 31.8 ± 7.4, with hip pain and positive impingement test. Stereo-radiographic images were acquired in three positions (neutral standing, neutral sitting, and flexed-forward-sitting). PI, pelvic tilt (PT), and sacral slope (SS) were measured. Repeatability was evaluated. Pelvic mobility was calculated as ΔPT and ΔSS from (i) standing to sitting, (ii) neutral to flexed-forward-sitting, and (iii) maximum to minimum values. Correlations of PI with PT, SS, ΔPT, and ΔSS were assessed.

Results: Repeatability was excellent for all pelvic mobility measurements (intraclass correlation coefficients, ICC > 0.97). ΔPT was 25.9 ± 8.3º from standing to sitting, 14.4 ± 11.2º from standing to flexed-forward-sitting, and 37.8 ± 13.7º from maximum to minimum values. ΔSS was 24.0 ± 7.6º from standing to sitting, 14.2 ± 11.6º from standing to flexed-forward-sitting, and 35.9 ± 13.7º from maximum to minimum values. PI was strongly correlated with PT in standing (r = 0.7) and SS in standing (r = 0.7), and moderately correlated with PT in sitting (r = 0.6) and SS in sitting (r = 0.5), but was not correlated with neither ΔPT nor ΔSS (r < 0.3).

Conclusion: Pelvic mobility, calculated as ΔPT and ΔSS, has excellent repeatability, and is not correlated with PI in non-arthritic patients with hip pain. Therefore, PI is of limited value for diagnosis and treatment of painful hips with positive impingement test, as well as to distinguish hip users from spine users; pelvic mobility should be used instead.

Level Of Evidence: Level IV.