We report on a case of muscle strain of the subscapularis muscle in a baseball player. An out-fielder (throws right-handed and bats left-handed) hurt his right shoulder while playing baseball. He complained of right-shoulder pain just after he forcefully hit his right hand against the fence in an attempt to jump and catch a flying ball with a glove on the left hand during a baseball game. Fat-suppressed T2-weighted magnetic resonance images (MRIs) of the right shoulder joint revealed muscle strain in the middle part of the subscapularis muscle, and the injury was surmised to have occurred on account of eccentric contraction of the subscapularis muscle. The case was considered to have moderate muscle strain, because he had modest muscle weakness with a negative lift-off test. Active stretching exercises were begun just after his first visit to our clinic, and throwing exercises were started 3 weeks later, by when the right-shoulder pain had completely disappeared. Repeat MRIs of the right shoulder joint obtained 4 weeks after his first visit to our clinic revealed a significant reduction of the high-intensity lesions in the subscapularis muscle. Conservative treatment was effective for managing moderate muscle strain of the subscapularis muscle. Muscle strain of the subscapularis muscle should be taken into consideration in the differential diagnosis of shoulder injuries in athletes.
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