Background/Purpose:  It is known that joint mechanics are involved in the hip osteoarthritis (OA) disease process.  In a previous study¹, several gait variables were lower in subjects with symptomatic hip OA compared to asymptomatic controls.  In the OA subjects gait variables were significantly correlated with radiographic OA severity but not pain.  It remains unclear, however, whether structural changes or clinical symptoms initiate the gait changes associated with hip OA.  In this study we tested the hypothesis that gait variables are different in people with symptomatic radiographic hip OA compared to those with radiographic changes but no symptoms.

Methods: 25 subjects with mild radiographic hip OA (Kellgren-Lawrence grade 2) were identified from an IRB approved repository of gait and radiographic data.  12 had been enrolled in a study of subjects with symptomatic unilateral hip OA and 13 came from a database of asymptomatic subjects.  Demographics and BMI were similar between the two groups (Table).  Gait analysis was performed with standard published methods: participants completed 3 trials per limb walking at a self-selected normal speed.  Kinematics and kinetics were calculated from marker positions and ground reaction forces.  Standard inverse dynamics methods were used.  The variables of interest were speed, dynamic hip range of motion, and peak 3D external moments normalized to body weight times height (%BWxHt).  Data were averaged for the 3 trials.  T-tests were used to compare gait variables between the two groups.    

Results: Walking speeds were not significantly different between the two groups (Table). The peak adduction and internal rotation moments were 17% and 29% lower in the symptomatic OA group compared to the asymptomatic group (p=0.017 and p=0.044, Table).  The external rotation moment was 26% lower in the symptomatic group (trend p=0.059). No other comparisons were statistically significant.

Conclusion: Subjects with mild symptomatic radiographic hip OA had different gait than subjects with mild radiographic OA alone.  Notably, walking speeds were similar between groups.  Thus gait differences observed were not attributable to slower speeds in the symptomatic group. The adduction, internal rotation, and external rotation moments, which each reflect aspects of hip abductor function, were reduced in the symptomatic group.  This suggests that this muscle group plays an important role in early symptomatic OA. Further, these results support previous speculations that pain may be an initial stimulus that initiates joint loading alterations in hip and knee OA^1,2.

References: ¹Shakoor et al., Osteoarthritis Cartilage 18(Supp 2): S67, 2010. ²Thorp et al., Arthritis & Rheumatism. 57: 1254-60, 2007.

Acknowledgement: Rush Translational Science Consortium/Searle Foundation Pilot Projects Grant