Theoretically, tears of the supraspinatus or infraspinatus tendon (or both) decrease the abduction or external rotation strength in the shoulder joint. However, in the current study, muscle strength (ie, dominant/ nondominant) in abduction, external rotation, and internal rotation did not differ among players with no tears, those with isolated tears of the supraspinatus or infraspinatus tendon, and those with tears in both tendons. Ultrasonography revealed that, in most cases, the tears occurred at the humeral attachment site of the superior shoulder capsule. A previous magnetic resonance imaging study showed that no shoulders in patients with partialthickness tears demonstrated supraspinatus atrophy, suggesting that the function of the rotator cuff muscles does not deteriorate in these patients. These results suggest that the articular-sided partial-thickness rotator cuff tear itself may not decrease shoulder muscle strength because the tear may be present in the superior shoulder capsule.