Swimmer's Shoulder

Etiology

Swimming is a unique activity because it primarily utilizes the upper body for the propulsive force, with 90% of the driving force provided primarily by the torque generated from the shoulder. To swim at an elite level, each swimmer must log between 60,000 and 80,000 meters per week, equivalent to 30,000 strokes per arm. Fundamentally, the swim stroke requires the shoulder to move in range-of-motion extremes while tremendous muscular force is exerted upon the joint structures.[5][6][7] 

Various risk factors relate to swimmers' shoulders, including musculoskeletal, psychological, training, and lifestyle factors.[1] Musculoskeletal risk factors include strength and endurance, shoulder posture, proprioception, glenohumeral instability, and scapular dyskinesia.[8][9] Load, distance, technique, years of experience, competitive level, stretching, and cross-training are some training risk factors associated with swimmers' shoulders.[10][11]

The cause of pain in such a condition is usually multifactorial and includes instability and laxity of the shoulder, overuse and fatigue of the rotator cuff muscles, impingement of the tendons under the coracoacromial arch, dyskinesia of the scapula, and anatomical variations like os acromiale.[12][13]

Laxity and Multi-direction Instability: Normally, in a shoulder joint, excessive translation of the humeral head on the glenoid is prevented by a combination of static stabilizers (that include ligaments and labrum), as well as dynamic stabilizers (that include the rotator cuff muscles). There are many reports of laxity of the static stabilizers of the shoulder joint in most competitive swimmers.[12][14] This stresses the rotator cuff muscles to balance the joint biomechanics, causing dysfunction.[2]

Overuse: Competitive swimmers undergo frequent and excessive shoulder revolutions in a day, during which serratus anterior and subscapularis muscles get fatigued as they are active during most of the pull-through phase. The kinematics of the shoulder are adversely affected by muscle fatigue, leading to shoulder pain and secondary impingement.[15][2]

Impingement:  Competitive swimmers suffer from impingement chiefly due to muscle fatigue and laxity. Due to the excessive laxity, there is increased glenohumeral translation that impinges on the rotator cuff tendons. The impingement can be subacromial, seen in forward flexion and internal rotation (recovery phase of stroke), or intra-articular, as seen in forward flexion, adduction, and internal rotation (hand entry phase of the stroke).[16]

Scapular Dyskinesia: When the serratus anterior and subscapularis muscles are fatigued, there is unopposed action of the pectoralis major that strains the anterior glenohumeral joint. This causes abnormal scapular movements, leading to secondary impingement and causing labral tears and shoulder pain. Abnormal scapular movements can also be associated with suprascapular nerve entrapment when with contraction of the infraspinatus and hyperelasticity.[17][18]

Epidemiology

Depending on the study, swimmer's shoulder incidence ranges from 3% to 70%. When defined as shoulder pain that interferes with training or progress in training, the incidence is approximately 35% in elite and senior-level swimmers.[19] Some studies report that around 91% of swimmers suffer from this condition during their entire sports career. This results in many swimmers missing training sessions and important competitive events.[20][10]

Pathophysiology

Swimming strokes can be broken down into pull-through and recovery phases. The latissimus dorsi and the pectoralis major are the primary contributors to the propulsive forces of the swim stroke through adduction and internal rotation. The subscapularis and serratus anterior muscles also play an integral role in the freestyle stroke.[2][21][22][19]

The freestyle stroke can be divided into six distinct parts/phases:

• Hand entry
• Forward reach
• Pull through
• Middle pull through
• Hand exit
• Middle recovery

The athlete needs to have properly balanced shoulder muscle strength. Improper muscle balancing can lead to the onset of shoulder pain. An absolute or sudden increase in training yardage and poor technique can also be associated with pain onset. The coaching staff can observe a dropped elbow during the recovery phase of the freestyle stroke as one of the early signs of possible injury. 

In a detailed electromyographic and cinematographic research of the normal freestyle stroke to find differences between painful and non-painful shoulders, Pink et al found that the action of the serratus anterior muscle dramatically decreases during the middle pull-through phase, leading to a compensatory action of the rhomboids, resulting in the destabilization of the scapula. Similarly, the subscapularis muscle becomes fatigued due to its prolonged activity, which leads to a compensatory activity of the infraspinatus muscle; this causes a disturbance in the balance of glenohumeral stabilization.[23][15]

A painful internal rotation movement may cause a drop of the elbow during the recovery phase of the freestyle stroke, thereby lowering the rotational demand and decreasing the pain. Also, such swimmers with painful shoulders may show exaggerated body roll as well as winging of the scapula. These signs can help with the early detection of swimmer's shoulder.[23]

History and Physical

The chief complaint in this condition is primarily anterior shoulder pain, aggravated by shoulder movements.[8] Due to the pain, often the swimmers need to skip some training or competitive events. As with most physical ailments, a thorough physical examination is imperative for diagnosing a swimmer's shoulder pain. The shoulders should be checked for atrophy and symmetry, and the range of motion should be measured. There should be a detailed evaluation of the shoulder joint's range of motion. 

A systematic review reported that decreased glenohumeral joint internal rotation movement and either increased or decreased external rotation movement are significant risk factors for shoulder pain in swimmers.[9] Particular attention should be paid to scapular positioning at rest and symmetry in motion to assess for abnormal motion. Strength testing likely will produce pain, and in advanced cases, the shoulder may fail to resist the examiner's force.[24]

Special testing may provide further insight. The apprehension/relocation test and sulcus test offer provide insight into instability. The Hawkins test is a valuable and sensitive exam in diagnosing subacromial impingement. In patients with positive laxity test results, the examiner should also check other joints for laxity to rule out a generalized condition.[2]

Evaluation

Although the condition is usually identified clinically, some imaging investigations, including radiography, ultrasonography, CT, and MRI, are often required to confirm the diagnosis.[19]

Plain-film radiographs are obtained initially to rule out any abnormal anatomic variations. Other pathologies, including calcification of the supraspinatus tendon, can also be identified on plain film images. Following evaluation by a sports medicine clinician, an MRI may be ordered to better identify pathology in the muscles, tendons, ligaments, and cartilage or to exclude other structural causes, such as labral cysts.

Although many shoulder diagnoses can be reached based on the physical examination alone, MRI is useful in confirming a diagnosis or when shoulder pain appears to have more than one source. An MRI arthrogram can be considered when a labral or tendon tear is suspected. Although imaging is integral to the diagnosis, caution is warranted in interpreting imaging because repetitive motion creates asymptomatic pathology in many athletes.[24]

Treatment / Management

Nonsurgical Management

Eliminating acute inflammation is the priority in shoulder rehabilitation. When a swimmer initially experiences pain, ice, NSAIDs, and rest can prevent progression. If pain continues or worsens, a 7- to 10-day course of NSAIDs and rest is ideal but often proves difficult if the injury occurs during the middle or late part of the season. At a minimum, effort should be made to reduce yardage to below the point of pain. For swimmers with impingement, tendinitis, or scapular dyskinesis, a subacromial and/or glenohumeral corticosteroid injection may be beneficial diagnostically and for pain reduction.[25][26]

Stretches focusing on the posterior capsule are important for preventing and reversing impingement. When coupled with overstretching of the anterior capsule, swimmers can create imbalances that worsen impingement. The swimmer can stretch the posterior capsule by horizontally adducting the arm and using the contralateral arm to pin it against the body.

Disproportionately increased adduction strength and internal rotation are unavoidable consequences of swimming. Overdevelopment of the pectoralis major and latissimus dorsi muscle groups creates a force that displaces the humeral head anteriorly, leading to joint instability. Additionally, strengthening the rotator cuff will restore muscular balance, reducing or eliminating impingement. As muscle endurance and strength improve, sport-mimicking exercises can be attempted, followed by low-yardage workouts at slow speeds, as long as the swimmer is pain-free and progressing slowly until the swimmer can return to competition.[27][28]

Surgical Management

Surgery is appropriate for structural pathologies. An athlete may elect symptomatic management rather than surgery, so they may continue competing until the pain begins to interfere with daily life. A capsular plication or inferior capsular shift procedure should be considered for swimmers with persistent multidirectional instability. Athletes should be aware, however, that training volumes may need to be reduced permanently to avoid pain. A subacromial exploration and removal of the hypertrophied, inflamed, and scarred tissue (thereby maintaining the structural integrity of the shoulder) is an option for athletes who obtain only limited relief from physical therapy. The next treatment option for swimmers with a labral tear in whom nonsurgical treatment has failed is labral debridement or repair.

Differential Diagnosis

Differential diagnosis includes the following:

• Multidirectional instability

• Partial articular side tear of rotator cuff

• Partial-thickness bursal-sided rotator cuff tear

• Posterior inferior humeral ligament avulsion

• Rheumatoid arthritis

• Shoulder dislocation

• Subacromial  bursitis

• Superior labrum lesions

• Supraspinatus tendonitis

• Thoracic outlet syndrome[24]

Prognosis

Most patients experience significant relief from symptoms after nonoperative management of the swimmer's shoulder. These athletes can return to sports after a few months of successful rehabilitation. Some patients require surgical management for their condition when conservative measures are ineffective or not expected to provide complete relief.

Swimming activities can be resumed after surgery, depending on the procedure and the patient's comfort level. However, after some procedures, such as capsular plication for multi-directional instability, the training volumes may need to be reduced permanently to avoid pain.[24]

Complications

Some of the complications that may be seen after surgical management include:

• Infection
• Persistent pain
• Decreased range of movement of the shoulder (stiffness)
• Prolonged rehabilitation requirements[24]