Tommy Kahnle—one of the New York Yankees’ most reliable relief pitchers last year—is going on the disabled list. His performance was poor early in the season, which he ascribed to lost velocity in his fastball. While shoulder pain was never mentioned, a recent news report describes MRI findings of “biceps and shoulder tendinitis”.

The biceps anchors in two places in the shoulder. One of the anchor tendons passes right through the joint. Changes in this part of the biceps tendon are expected with age. They accompany the expected age-related changes in the small muscles that rotate the shoulder. The tendons (parts that the muscles use to move the bones) of those small muscles are flat and thin and cover (or cuff) the head (the ball) of the shoulder joint. After age 40, we all develop rotator cuff tendinopathy. There is thinning of the tendons and defects may develop. Genetic factors likely affect how quickly this advances.

Throwing athletes get tendinopathy at a younger age and in a slightly different form. Studies of professional baseball pitchers with no symptoms often find MRI changes in the biceps and rotator cuff tendons (https://www.ncbi.nlm.nih.gov/pubmed/12975193). That makes it difficult to be sure when an MRI finding is causing symptoms and when it is just an incidental finding.

It’s not clear if the doctors treating Tommy found something more than the typical changes on MRI. And it’s not clear how they have decided that Tommy’s symptoms are likely related to the findings. Periods of rest and a routine of shoulder strengthening exercises are often tried to calm the symptoms and increase throwing effectiveness.

This article was made by Paul Bonilla and David Ring