Practice Essentials
Swimmer's shoulder is the term used to describe the problem of shoulder pain in the competitive swimmer. Swimming is an unusual sport in that the shoulders and upper extremities are used for locomotion, while at the same time requiring above average shoulder flexibility and range of motion (ROM) for maximal efficiency. This is often associated with an undesirable increase in joint laxity. Furthermore, it is performed in a fluid medium, which offers more resistance to movement than air. This combination of unnatural demands can lead to a spectrum of overuse injuries seen in the swimmer's shoulder, the most common of which is rotator cuff tendinitis. [1]
Signs and symptoms of swimmer's shoulder
Pain that is associated with swimmer's shoulder has the following characteristics:
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The pain is often poorly localized and felt to be deep within the shoulder
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Initially, the pain is noted only during or immediately after swimming
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Occasionally, the pain can be associated with a particular position or phase of the stroke
See Presentation for more detail.
Diagnosis of swimmer's shoulder
Imaging studies
The following imaging studies may be helpful in the workup:
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Radiographs - An anteroposterior (AP) scapular Y or outlet view and axillary view of the shoulder should be obtained when the pain persists after 6 or more weeks of rest and rehabilitation
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Magnetic resonance imaging (MRI) - If imaging is required, MRI is the study that is most likely to be helpful for determining the source of injury in swimmer's shoulder
Diagnostic procedures
Procedures that may be helpful in the workup include the following:
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Subacromial injection - This can be a useful test in the older swimmer whose condition has failed to respond to rest and rehabilitation, suggesting a partial or complete rotator cuff tear
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Intra-articular injection - Injection within the glenohumeral joint with lidocaine alone or with a corticosteroid can be a diagnostic as well as therapeutic procedure
See Workup for more detail.
Management of swimmer's shoulder
In the acute phase, the treatment of swimmer's shoulder is primarily with physical therapy. Surgical intervention may be considered for athletes who have persistent pain.
See Treatment and Medication for more detail.
Etiology
As the shoulder is pushed to its limits of strength and endurance, the rotator cuff muscles generally fatigue before the power muscles, allowing micromotion and subluxation of the humeral head. This, in turn, decreases stroke efficiency, while leading to injuries of the rotator cuff, biceps tendon, and glenoid labrum.
Superior subluxation of the humeral head is particularly problematic as it can impinge the rotator cuff tendons against the acromion above, leading to tendinitis and/or tears. The overlying subacromial bursa (also referred to as the subdeltoid bursa) often becomes inflamed, leading to painful bursitis.
A study of risk factors for shoulder pain and instability in 236 female competitive swimmers concluded that symptomatic swimmers younger than 12 years of age had reduced shoulder flexibility, weakness of the middle trapezius and shoulder internal rotators, and latissimus dorsi tightness, whereas symptomatic swimmers aged 12 years or older had pectoralis minor tightness and decreased core endurance. [2] A study in 201 competitive swimmers (96 male, 105 female) who were initially pain free concluded that posterior shoulder muscle endurance and hand entry error were among the strongest predictors for the development of shoulder pain. [3] In a study that included 76 young competitive swimmers (mean age, 14 years), Mise et al found that hypomobility and hypermobility of the shoulder complex were risk factors for shoulder pain in male and female swimmers, respectively. [4]
A study of electromyographic activity of selected shoulder girdle muscles in elite swimmers with and without shoulder pain found that swimmers with pain had greater activation of the upper trapezius, serratus anterior, and latissimus dorsi muscles, but found no difference in the activation of the middle and lower trapezius, middle deltoid, and sternocleidomastoid muscles. These researchers suggested that "altered muscle activation patterns may contribute to the painful shoulder in elite swimmers and need to be considered within the rehabilitation interventions." [5]
Epidemiology
The incidence of swimmer's shoulder in the United States has been reported to be as low as 3% and as high as 67%. When specifically defined as "significant shoulder pain that interferes with training or progress in training," an incidence of 35% has been reported in elite and senior level swimmers. [6]
Functional Anatomy
The shoulder girdle is made up of 3 bones (the scapula, clavicle, and proximal humerus), 2 joints (the glenohumeral and acromioclavicular joints), and numerous ligaments, muscles, and tendons. The subacromial bursa overlies the rotator cuff and can provide it with some mechanical protection from the bony acromion above in the face of impingement.
The key ligaments are the glenohumeral ligaments (inferior, middle, superior), which are thickened regions of the joint capsule, of which the inferior glenohumeral ligament is most important. Their role is to help stabilize the glenohumeral joint, in support of the rotator cuff muscles.
The key muscle group of the shoulder is the rotator cuff, made up of (from anterior to posterior) the subscapularis, supraspinatus, infraspinatus, and teres minor. The primary role of the rotator cuff is to function as the dynamic and functional stabilizer of the glenohumeral joint. The long head of the biceps tendon, located between the subscapularis and supraspinatus, also assists the rotator cuff in stabilizing the glenohumeral joint. These muscles and their tendons can be overused and injured in shoulder dominant activities such as swimming, with the most commonly injured portion of the cuff being the supraspinatus. On the other hand, the "power muscles" of the shoulders, including the latissimus dorsi, pectoralis, and deltoid, are responsible for moving the arm through space or water, but only infrequently sustain significant injury.
Finally, the trapezius, levator scapulae, rhomboids, and serratus anterior muscles stabilize and position the scapula and shoulder girdle, and are therefore very important to the swimming stroke. Without a stable platform from which to work, the shoulder and arm cannot function efficiently. Fortunately, they also are only occasionally the source of significant injury in the swimmer.
Sport-Specific Biomechanics
The 4 basic strokes used in competitive swimming are the freestyle, backstroke, breaststroke, and butterfly. Biomechanically, each stroke can be divided into as many as 5 different phases; however, for the purpose of this article, each stroke is divided into two main phases: propulsion and recovery. [7]
Strength and power are required for maximal propulsion, while flexibility is required for an efficient and faster recovery. Increased shoulder flexibility and ROM are beneficial to all strokes but can result in increased laxity of the glenohumeral joint capsule and ligaments, the static stabilizers of the shoulder. This laxity must then be compensated for by a stronger rotator cuff, to keep the humeral head centered in the glenoid socket during stroke activity, a requirement for efficient stroke work as well as to avoid injury to the labrum and cuff.
To better understand how the shoulder works in swimming, it may be helpful to think of the upper extremity as a lever or "canoe paddle" mechanism. The swimmer's hand functions as the flat end of the paddle. The rotator cuff functions as a fulcrum stabilizing the glenohumeral joint so that the power muscles of the shoulder are able to pull the arm through the water. This would be analogous to the way in which a canoeist uses one hand to stabilize the upper end of a paddle as a fulcrum, so that the lower hand can pull the paddle through the water more efficiently.
A study by Hibberd et al found that over the course of 12 weeks of training, swimmers had greater decreases in subacromial space distance and an increase in forward shoulder posture compared to nonoverhead athletes. [8]
Prognosis
The prognosis for a full recovery with appropriate rest and rotator cuff rehabilitation is good. Surgery is seldom required except in the most recalcitrant cases.
Patient Education
Educating athletes, parents, and coaches can go a long way toward successful rehabilitation and avoiding recurrent injuries. The role and importance of the rotator cuff in the swimmer's shoulder should be emphasized, and hence the importance of completing a shoulder rehabilitation program.
For patient education resources, see Rotator Cuff Injury and Shoulder Impingement Syndrome.
