Hip range of motion is differentially associated with pain sensitivity in individuals with and without knee...

Knee osteoarthritis (KOA) is a multifactorial condition influenced by both mechanical and neurophysiological factors. Hip joint mobility may be associated to knee joint loading and pain processing; however, the relationships between hip range of motion (ROM), pain sensitivity, and muscle torque in individuals with KOA remain unclear. This study aimed to investigate the association between knee pain sensitivity and hip rotator ROM in individuals with and without KOA. Additionally, it examined the association between hip rotation ROM and muscle torque and compared hip ROM between groups.

This cross-sectional comparative study included 38 participants (26 with KOA and 12 healthy controls). A comprehensive physical assessment was conducted, including evaluation of both hip and knee range of motion (ROM) across multiple hip movements (flexion, extension, abduction, adduction, and internal and external rotation), measured using a digital inclinometer and a universal goniometer. Hip muscle torque was assessed using isokinetic dynamometry. Pain sensitivity was evaluated through Quantitative Sensory Testing, including pressure pain threshold (PPT), temporal summation (TS), and conditioned pain modulation (CPM). Group comparisons were performed using analysis of covariance (ANCOVA). Multiple linear regression models were used to examine the association between hip rotational ROM and pain sensitivity, including interaction terms for group.

No significant differences in hip or knee ROM were observed between groups. However, a significant interaction between total hip rotation and group was found for PPT at the knee joint line (p = 0.039; adjusted R² = 0.372). Specifically, in the control group, greater hip rotational ROM was associated with higher PPT values (β = 0.068), indicating lower pain sensitivity. In contrast, in individuals with KOA, greater hip rotational ROM was associated with lower PPT values (β = - 0.047), indicating higher pain sensitivity. No significant associations were observed for muscle torque, temporal summation, or conditioned pain modulation.

The association between hip ROM and pain sensitivity appears to differ according to the presence of KOA. These findings suggest that proximal mobility may be differentially related to pain sensitivity measures depending on clinical status, supporting the need for further investigation into hip-related factors in individuals with KOA.