Snapping Scapula Syndrome

Etiology

The scapulothoracic joint is padded by the serratus anterior and subscapularis muscles and bursae^(4,5). The superomedial, inferomedial angle, and medial border are less cushioned by underlying muscles and bursae. Therefore, the friction at the scapulothoracic joint increases⁽⁴⁾. Irregular anterior curvature of the superomedial angle of the scapula decreases the space at the scapulothoracic joint. Normal angle is measured to be between 124 degrees – 162 degrees. However, less than 142 degrees increases the chances of SSS⁽⁴⁾.

There are multiple other reasons why the scapular-thoracic friction may increase and result in SSS. Scapular dyskinesia is one such cause and has many neuro-musculoskeletal causes. The scapula’s abnormal movement brings it closer to the ribcage⁽⁴⁾. Atrophy of the subscapularis and serratus anterior may reduce their cushioning effect, resulting in friction at the scapulothoracic joint. Furthermore, scapula and rib fracture complications may increase friction among the scapulothoracic structures^(4,5). Anatomical variations may increase the risk of developing SSS. The Luschka tubercle is a hooked-shaped bony protuberance located at the superior aspect of the medial border of the scapula, which may reduce the space between the scapula and the ribcage^(4-7).

Bursae around the scapulae

Two major bursae:
1. Infraserratus bursae: between the serratus anterior muscle and the chest wall.
2. Supraserratus bursae: between subscapularis and serratus anterior muscles.

 

Four adventitial/minor bursae:
Two located at the superomedial angle of the scapula:
1. Infraserratus bursae: between the serratus anterior muscle and the chest wall
2. Supraserratus bursae: between subscapularis and serratus anterior muscles 

One at the inferior angle of the scapula:
3. Infraserratus bursae: between the serratus anterior muscle and the chest wall. 

One at the Spine of the scapula:
4. Trapezoid bursae: between the medial spine of scapula and the trapezius.

Clinicians must also consider bursitis, bone tumors, and elastofibromas as possible causes of increased friction. Bursitis may result from a single traumatic event, repetitive movements, or scapular dyskinesia⁽⁴⁾. The bursae may scar and become fibrotic, leading to the snapping/clicking sound⁽⁵⁾. Osteochondroma or exostosis is the most common benign primary bone tumor of the scapula, and elastofibromas are benign soft tissue tumors⁽⁴⁾.

“Snapping scapula syndrome is a relatively uncommon condition, and research is scarce.”

Clinical Presentation 

Clinicians must complete a thorough assessment when suspecting SSS. Athletes are typically involved in overhead sports, such as swimming or throwing, and description of audible clicking/snapping/crepitation with active shoulder movement, including shrugging. They experience pain with overhead activities, with shoulder abduction the most aggravating. Horizontal adduction lifts the scapula from the ribcage and eases its symptoms^(1-8).

Furthermore, their pain is often located at the superomedial angle or, less often, the inferior pole of the scapula, and the region is tender to palpation. In cases where there may be an underlying mass, athletes will present with fullness in the scapular region. They may also present with scapular winging, dyskinesia, and thoracic kyphosis^(1-8). 

Imaging

Clinicians must know which studies or imaging will assist in diagnosing the suspected pathology, as this will inform the referral pathway. X-rays are the primary imaging option available to clinicians. They should obtain a lateral scapular view (tangential or oblique view) and AP and axillary views in the scapular plane. This will identify any obvious bony causative factors^(2,9).

If an X-ray is clear but the athlete continues complaining of unexplained pain, clinicians can perform CT scans for a more in-depth analysis. Moreover, MRI will identify soft tissue lesions such as inflamed bursa or space-occupying lesions^(2,9). 

Conservative Management

Clinicians should advise athletes to trial conservative management for 6-12 months before considering surgery⁽⁶⁾. Conservative treatment is more successful when the cause is overuse rather than due to an anatomical lesion^(5,6).

Pain reduction: Since the leading causes of SSS are overuse and poor movement mechanics, activity modification and load management may be necessary in the initial phases⁽⁵⁾. Oral NSAIDs or cortisone injections into the bursae may be required in patients with high-intensity pain or when non-invasive measures fail⁽⁶⁾. Topical anti-inflammatories and ice application may also be an option.

Postural correction: Rehabilitation for SSS should focus on the functional role of the scapula during shoulder movement and emphasize postural considerations, such as correcting forward head posture, thoracic kyphosis, and protracted shoulders^(5,6,9). For example, clinicians may use visual cues to assist the athlete with postural adjustments.

Strengthening: Scapular, upper back, and rotator cuff muscle strengthening establishes a stable foundation for the shoulder. Progression along the rehabilitation loading stages (e.g., isometric to isotonic and eventually eccentric endurance scapular exercises) will facilitate load management. Strengthening should initially be done in the closed kinetic chain due to its contribution to stability. Clinicians can incorporate scapular core exercises such as scaption, low rows, lawn mower, and push-up plus. Emphasis should then be placed on eccentric scapular control. It is essential to ensure stability and optimal posture during strengthening exercises. Lighter loads and more repetitions are appropriate for endurance training, and clinicians must focus on the correct biomechanics.

Stretching: Depending on the assessment outcome, clinicians may encourage athletes to stretch muscles identified to facilitate SSS. These could include the pectoralis major and minor, levator scapulae, upper trapezius latissimus dorsi, subscapularis, sternocleidomastoid, rectus capitis, and scalenes⁽¹⁰⁾. The optimal length of these muscles may facilitate the desired scapulohumeral rhythm. Maintaining the mobility of the thoracic spine and GHJ is also essential.

Ergonomics: Clinicians need to identify and address workplace contributions to poor posture. 

Surgical Management

Clinicians can consider operative management when conservative management fails to produce adequate symptomatic relief. Outcomes of surgical intervention may be more reliable if patients experience relief following a local anesthetic injection into the inflamed bursae⁽⁹⁾. Therefore, a lack of relief following an injection should be considered a contra-indication to surgery. Researchers from the Steadman Phlippon Research Institute in the USA found that of the patients who underwent an arthroscopic bursectomy and partial scapulectomy, 90.5% returned to sport, and 73.8% returned to their previous level of performance⁽¹¹⁾.

“Athletes are typically involved in overhead sports, such as swimming or throwing…”

Conclusion

Snapping scapula syndrome is a relatively uncommon condition, and research is scarce. Clinicians are tasked with the challenging responsibility of making an accurate diagnosis based on a presentation that they may not have seen before. It is vital to have a thorough understanding of the shoulder anatomy and physiology. To obtain an accurate diagnosis, clinicians are required to conduct a detailed subjective and objective evaluation. Identifying patient goals and level of performance/work early on is also crucial as this will guide their management and the rehabilitation process.

References

1. Orthopedics.2016; 39(4): 783-786.
2. Sports Health.2021;14(3): 389–396. 
3. Anas Res Int.2013; 1–9. 
4. Radiologia Brasileira.2019; 52(4): 262–267. 
5. Arthroscopy.2009 25(11) 1298–1311.
6. Am J Sports Med.2004; 32(6): 1554–1565. 
7. Arch Phys Med Rehabil.1997; 78(5): 506–511. 
8. Clin Sports Med.2014; 33(4): 757–766. 
9. J Am Acad Orthop Surg.2013;21(4) 214-224.
10. Muscle, Ligaments and Tendons J.2013; 3(2): 80–90.
11. Am J Sports Med. 2024;52(6):1449-1456.