Relationships between self-perceived and clinical expression of pain and function differ based on the underlying pathology of the human hip

Background: Patient-reported outcomes are commonly used to assess patient symptoms and track post-operative improvements. The effect that specific hip pathology has on the relationship between perceived and objectively measured symptoms remains unclear. The purpose of this study was (1) to evaluate differences of function and pain in FAIS and DDH patients, (2) to assess the correlation between perceived and true functional ability, and (3) to determine the influence of pain on measures of function. Methods This prospective cross-sectional study included 73 pre-operative patients with femoroacetabular impingement syndrome (FAIS) and developmental dysplasia of the hip (DDH), who were diagnosed based on clinical history, physical examination, and radiographic findings. Objectively measured function (6-minute walk test [6MWT], single leg hop test [SLHT], Biodex sway test [BST], hip abduction strength test [HABST], and STAR excursion balance reach tests [STAR] in multiple directions), patient-reported function (UCLA Activity scale, Hip Outcome Score [HOS] activities of daily living [ADL] and Sport subscales, Short Form 12 [SF-12] Physical Activity subscale, and the Hip Disability and Osteoarthritis Outcome Score [HOOS] ADL and Sport), and patient-reported pain data (HOOS Pain, visual analogue scale (VAS), and a pain location scale with eight bilateral body locations) were collected during pre-surgical clinic visits. Patient demographics were compared using independent two-sample t-tests. Between-group comparisons of patient scores were performed using Wilcoxon Rank-Sum tests. Within-group relationships between pairs of outcome variable were analyzed using Spearman’s rank correlation coefficients. The level of significance for all statistical tests was set at α = 0.05 (two-tailed). Results 6MWT was moderately-to-strongly correlated with nearly all patient-reported measures of function (FAIS: r = 0.34–0.62, DDH: r = 0.27–0.56). In FAIS patients, only HOOS Pain was significantly correlated with an objective measure of function, which was 6MWT (r=-0.53). However, in DDH patients, patient-reported pain scores were moderately correlated with a number of objective measures of function (r=-0.32–0.48). Conclusion FAIS patients reported significantly higher function and lower pain compared to DDH patients. No single patient-reported measure of function was broadly significantly correlated with objective measures of function in either patient group. Functional performance in patients with DDH appears to be influenced by self-perceived pain.