Forearm Muscle and Tendon Thickness in Rotator Cuff-Related Shoulder Pain

Rotator cuff-related shoulder pain (RCRSP) is one of the leading causes of shoulder pain and disability in adults. In addition to local impairments such as pain, muscle weakness, and reduced range of motion, individuals with RCRSP frequently demonstrate altered upper extremity movement patterns and reduced functional performance. These adaptations may extend beyond the shoulder joint and influence distal segments of the upper extremity. Previous research has primarily focused on structural changes in the rotator cuff muscles and tendons, scapular musculature, and shoulder biomechanics. However, the potential morphological adaptations of the forearm muscles and tendons remain largely unexplored. Persistent pain, reduced upper limb use, altered neuromuscular control, and compensatory motor strategies associated with prolonged shoulder symptoms may contribute to changes in forearm muscle and tendon morphology. Understanding these adaptations may improve the current understanding of the regional effects of RCRSP. Musculoskeletal ultrasonography provides a valid, reliable, non-invasive, and accessible method for evaluating muscle and tendon morphology. The increasing availability of portable ultrasound devices has expanded the feasibility of assessing musculoskeletal structures in both clinical and research settings. Despite these advantages, ultrasonographic evaluation of forearm muscles and tendons has rarely been performed in individuals with RCRSP. This cross-sectional study aims to investigate the association between symptom duration and forearm muscle and tendon thickness measured by portable ultrasonography in individuals with RCRSP. The study also seeks to explore whether structural changes in the forearm are accompanied by alterations in hand grip strength, pain intensity, and upper extremity function. The findings may contribute to a better understanding of distal musculoskeletal adaptations associated with prolonged shoulder pain and provide evidence for incorporating forearm assessment into rehabilitation programs for individuals with RCRSP.