Ultrasound Findings in the Shoulders of U.S. Olympic Swimmers
By Dr. Yi-Cheng Wu · Reviewed June 21, 2026
For athletes with swimmer's shoulder, adding a dynamic assessment to the static ultrasound examination can reveal rotator cuff and bursal findings that stay hidden at rest.
Swimmer's shoulder is often related to rotator cuff tendinopathy and subacromial impingement, driven by the large volume of overhead movements in freestyle, butterfly, and similar strokes. For athletes, a shoulder ultrasound is recommended to add a dynamic examination on top of the static assessment (biceps tendon, supraspinatus and infraspinatus tendons, bursae, and labrum), observing impingement and humeral head motion through different positions such as abduction, internal rotation, and flexion. A study of 2008 U.S. Olympic swimmers found that although most had no restriction in range of motion, structural changes in the rotator cuff, bursae, and other tissues were still visible, some accompanied by ligamentous laxity. Whether this is related to joint hypermobility remains to be clarified by further research.
Today in clinic I was talking with a triathlete. The location of injury tends to differ a little from sport to sport, and in swimming the swimmer’s shoulder has long been a difficult problem, because it has many causes. There are a few key things that always need to be checked and confirmed, and these differ somewhat from the common static ultrasound examination. For athletes, adding a dynamic examination to the ultrasound often turns up many new findings.
This study from an American sports medicine journal is unusual, because the participants were all elite athletes: swimmers from the 2008 U.S. Olympic team, who provided information on their training, injury history, and ultrasound findings.
The most common causes of swimmer’s shoulder are rotator cuff tendinopathy and subacromial impingement, because the typical swimming stroke involves flexion, adduction, and extension of the shoulder combined with internal rotation. The large amount of overhead movement can lead to shoulder laxity, which then requires more muscular effort to control the whole shoulder. If overuse leads to muscle fatigue and the underlying condition is repeatedly ignored, it can result in later swimmer’s shoulder discomfort.
The entry phase of the freestyle stroke is a typical movement that can cause subcoracoid impingement or abnormal humeral head motion, and this movement appears in both freestyle and butterfly. Muscle imbalances are also common, such as a tight pectoralis minor accompanied by scapular protraction.
The soft-tissue structures of competitive athletes show some distinctive changes from repetitive movement that differ from those of the general population, including changes in the rotator cuff, bursae, and labrum. The exact reason for these structural changes is not yet clear, but both overdiagnosis and neglect may be linked to later discomfort.
Static ultrasound assessment
- Biceps tendon
- Condition of the bicipital groove (normal, cystic change, effusion, and so on)
- Changes in the supraspinatus and infraspinatus tendons
- State of the bursae
- Changes at the tuberosity attachment sites
- Changes in the labrum
Dynamic ultrasound assessment
- Impingement of the subacromial bursa
- Motion of the humeral head
- Subacromial distance and bursal thickening
- Impingement of the subcoracoid bursa
- Condition of the acromioclavicular joint
The dynamic assessment is not just about movement; it also needs to test from different positions, including abduction, internal rotation, and flexion.
Among these 42 athletes, the average swimming experience was 15.4 years, with an average of 6,116 meters per practice session and roughly 55,000 meters per week. Of them, 16 had pain during competition and 4 had shoulder instability.
None of the athletes had restriction in range of motion, yet discomfort and abnormal findings were still present. Interestingly, more than half of them had ligamentous laxity (bending the fingers back to the forearm was seen in 62% of athletes, and elbow bending beyond 10 degrees in 57%). Whether these findings and the previously mentioned joint hypermobility are related to swimmers still needs further research to confirm.
Ultrasound findings
Biceps tendon abnormalities were present in 72%, and 7% of athletes even showed an obvious biceps tendon tear. Rotator cuff tendinopathy (including the supraspinatus and infraspinatus) reached as high as 96%, with about 22% showing partial tears; subdeltoid bursal thickening was seen in 83% and subcoracoid bursal thickening in 37%.
This study has some limitations. Although it found overuse to be an important factor in swimmer’s shoulder pain, it also found that age and years of training had little association with the severity of disease. The authors speculated that people who began having discomfort earlier may not have been able to become Olympic athletes, so they were not among the swimmers in this group.
Summary
As ultrasound technology and equipment develop, we are learning more and more about shoulder abnormalities. While the internal structures still need the help of MRI, dynamic ultrasound scanning leaves many lesions that stay hidden at rest with nowhere to hide. I look forward to finding more interesting cases in the future.
Further reading
How much swimming makes the shoulder ache?
Sport-specific injury: the swimmer’s shoulder you can’t ignore
The relationship between joint hypermobility syndrome and swimming
References
Clinical and Ultrasonographic Evaluations of the Shoulders of Elite Swimmers. Am J Sports Med. 2016 Dec;44(12):3214-3221.
Image source
Further reading
Frequently asked questions
Which structures does the static ultrasound assessment of the shoulder look at?
The static assessment includes the biceps tendon, the condition of the bicipital groove (normal, cystic change, effusion, and so on), changes in the supraspinatus and infraspinatus tendons, the state of the bursae, the tendon attachment at the tuberosities, and changes in the labrum.
How is the dynamic ultrasound assessment of the shoulder different?
The dynamic assessment observes impingement of the subacromial bursa, the motion of the humeral head, the subacromial distance and bursal thickening, subcoracoid bursal impingement, and the acromioclavicular joint, testing through different positions such as abduction, internal rotation, and flexion, which makes findings that stay hidden at rest easier to detect.
What did the ultrasound of the Olympic swimmers reveal?
In this group of athletes, biceps tendon abnormalities were seen in about 72%, rotator cuff tendinopathy in as many as 96% (with roughly 22% showing partial tears), subdeltoid bursal thickening in 83%, and subcoracoid bursal thickening in 37%, and more than half of them had ligamentous laxity. These are study findings and do not predict any individual's outcome.
What is the clinical takeaway of this study for swimmer's shoulder?
The study suggests that overuse is an important factor in swimmer's shoulder pain, but that age and years of training had little association with disease severity. As ultrasound technology advances, dynamic scanning can complement the limitations of the static examination, though some deep structures still need MRI for assessment.
This article is also available in the original Chinese, with the full reference list.
閱讀中文原文 · Read in Chinese