Altered weight-bearing compensatory neuromuscular control strategies in early-stage hip-related pain.

Introduction: Individuals with early hip-related pain may exhibit subtle compensatory neuromuscular alterations even when overall movement performance appears largely preserved, making these changes difficult to detect through routine observation. Whether modulation of stance width during a weight-bearing task can provoke and reveal these underlying control differences remains unclear. Methods: Participants with early hip-related pain and asymptomatic controls performed standardized squats under three stance-width conditions. Bilateral surface electromyography signals were recorded from the lower limbs during task execution. Time-varying electromyography and muscle synergy analyses were used to compare neuromuscular control characteristics between groups. Results: Both groups demonstrated three stable muscle synergy patterns across conditions. However, the hip pain group showed specific adaptations in synergy weights and activation timing, with group differences mainly observed during the squat-bottom holding phase and the transition to ascent. These differences became more pronounced as stance width increased. In addition, the hip pain group showed reduced maximal voluntary contraction strength, whereas electromyographic frequency-domain features remained relatively stable. Discussion: Early hip-related pain appears to be characterized more by task-dependent compensatory reorganization than by overt functional deficits. Modulation of stance width can effectively provoke aberrant movement patterns and, when combined with electromyographic monitoring, may serve as a useful research tool for identifying underlying neuromuscular control differences.