The study aimed to determine how well recorded pain levels and range of motion relate to patients' reported levels of functional ability/disability pre- and post- total hip arthroplasty.

Range of motion (ROM), Oxford Hip Score (OHS) and Self-Report Harris Hip Score (HHS) were recorded pre-operatively and 3 months post-total hip arthroplasty. Pearson's correlation coefficients were calculated to determine the strength of the relationships both pre- and post-operatively between ROM (calculated using the HHS scoring system) and scores on OHS and HHS and response relating to pain from the questionnaires (question 1 HHS and questions 1, 6, 8, 10, 11 and 12 of OHS) and overall scores.

Only weak relationships were found between ROM and HHS pre- (r = 0.061, n = 99, p = 0.548) and post-operatively (r = 0.373, n = 66, p = 0.002). Similar results were found for OHS, and when ROM was substituted for flexion range. In contrast, strong correlations were found between OHS pain component and HHS pre- (r = -0.753, n = 107, p<0.001) and post-operatively (r = -0.836, n = 87, p<0.001). Strong correlations were also found between the OHS pain component correlated with the HHS functional component only (HHS with score for questions relating to pain deducted) pre- (r = -0.665, n = 107, p<0.001) and post-operatively (r = -0.688, n = 87, p<0.001). Similar results were found when the HHS pain component was correlated with OHS.

In orthopaedic clinical practice ROM is routinely used to assess the success or failure of arthroplasty surgery. These results suggest that this should not be done. Instead, asking the patient the level of pain that they are experiencing may be a good determinant of level of function. The results of this study may aid the development of arthroplasty scoring systems which better assess patients' functional ability.