Sensorimotor incongruence is associated with increased symptom severity in people with frozen shoulder: a cross-sectional study

Introduction Frozen shoulder (FS) is a common musculoskeletal condition characterized by shoulder pain and range of motion restrictions. While traditionally considered nociceptive, recent research suggests central pain mechanisms may also be involved. Objective This study aimed to determine the effect of experimental sensorimotor incongruence (SMI) on pain and sensory disturbances in people with FS and asymptomatic controls. Methods The study included two groups: people with FS and asymptomatic controls. Participants underwent a bimanual coordination test with eight paradigms (four per side: congruent and incongruent with a mirror or whiteboard). Outcome measures were assessed immediately after each paradigm and consisted of pain, discomfort, perceived temperature or weight changes, experiencing an extra or loss of an arm, and feelings of peculiarity. Results A total of 69 participants were included (36 with FS and 33 asymptomatic controls). Results showed that people with FS experienced a significant increase in pain and sensory discomfort when exposed to SMI paradigms compared to controls. Both congruent and incongruent paradigms exacerbated pain levels, whereas changes in perceived weight were observed variably across congruent and incongruent movements. Conclusion These findings support the hypothesis that SMI plays a crucial role in pain modulation in FS, possibly through altered central pain processing and neuroplastic changes. The results highlight the need for therapeutic approaches addressing both musculoskeletal and neuroplastic components of FS.