Swimmer's shoulder involves injury to the tendons and tissues that support the shoulder complex, and is also known as shoulder impingement. Repeated strain of the shoulder joint can irritate soft tissue structures and lead to tiny tears causing inflammation and scar tissue.
Common symptoms include muscle weakness or fatigue, a loss of shoulder function, instability and pain. The supraspinatus tendon is thought to be most impacted, however, a recent study may dispute this. A cohort of elite swimmers were recruited of equal demographic and training load who were either symptomatic or asymptomatic for shoulder pain, underwent MRI.
Results showed that subscapularis and supraspinatus tendinopathy was the most common tendon abnormality identified, with a prevalence of 73% and 70% respectively. There was no significant difference between dominant and non-dominant shoulders for either tendinopathy, however, grade 3 tendinopathy was significantly more prevalent in subscapularis than in supraspinatus. Both the labrum and acromioclavicular joints were also reported to exhibit strain through MRI.
It is vital to understand the mechanics of any sport, so you know what structures may be more impacted than others. This will obviously dictate what treatment and rehabilitation approach will be most applicable to that given patient.
Holt, K. et al. (2022). Subscapularis tendinopathy is highly prevalent in elite swimmer's shoulders: an MRI study. Journal of Science and Medicine in Sport. 25(9): 720-725.