Swimmer's Shoulder: Targeting Treatment
Scott M. Koehler, MD; David C. Thorson, MDTHE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 11 - NOVEMBER 96
In Brief: Shoulder pain caused by impingement of subacromial tissues is a common overuse injury in swimming, especially among adolescents who may have rigorous training schedules and be skeletally immature. A case of a 14-year-old girl with swimmer's shoulder demonstrates the diagnostic work-up, which involves pertinent history, inspection, palpation, and assessment of strength, impingement, and instability. Treatment focuses on icing, relative rest, physical therapy, and modifying the swimming workout to reduce overuse and impingement.
Shoulder pain, the hallmark of swimmer's shoulder, is the most common musculoskeletal complaint among competitive swimmers (1). Interfering shoulder pain is reported to be present in 9% to 35% of competitive swimmers, while 38% to 75% of competitive swimmers have a history of shoulder pain (2-4).
Swimmer's shoulder was first described in 1974 as a common, painful syndrome of repeated shoulder impingement in swimmers (4). The term "swimmer's shoulder" generally refers to subacromial impingement syndrome and related dysfunction in swimmers (5). It is most common with the freestyle and butterfly strokes, but can also occur with the backstroke.
A 14-year-old female swimmer presented with left shoulder pain. She said the pain occurred during swimming and was most bothersome during freestyle and butterfly strokes; it worsened during difficult workouts and occasionally persisted afterward. The pain was not alleviated with icing after practice or with 2 to 3 days of rest.
The patient reported that she swam 8,000 to 10,000 yd a day, five or more days each week, and weight trained three times a week using her own program. She also complained that her times had not improved as expected over the summer swim season. There was no history of shoulder injury or dislocation.
The patient sat with her shoulders slightly slouched forward during the examination. The patient's posterior shoulder musculature was underdeveloped bilaterally on inspection and on palpation of the rotator cuff and scapular stabilizers. She had mild winging of the left scapula. Palpation of the acromioclavicular joint and the coracoid process produced no pain, although there was tenderness to palpation of the impingement interval. There was also tenderness to palpation of the left biceps and supraspinatus tendons. The patient had full range of motion on flexion, abduction, and internal and external rotation.
Strength testing revealed slightly decreased strength of the supraspinatus and infraspinatus muscles bilaterally. She had full strength of the internal rotators, arm extensors, and arm flexors. The patient had moderate anterior and posterior laxity of both shoulders and bilateral positive sulcus signs. Impingement and adduction-compression tests of her left shoulder were positive, but the apprehension test was negative. Neck and elbow exams revealed no abnormalities.
Anteroposterior, outlet, and axillary radiographs of the shoulder were obtained. They revealed no soft-tissue or bony abnormalities, specifically no subacromial narrowing or spurring of the acromion.
The diagnosis was left-sided impingement syndrome consistent with swimmer's shoulder, including multidirectional instability and weakness of the rotator cuff and scapular stabilizers.
Treatment included episodic icing, anti-inflammatory medications, physical therapy, and relative rest. Physical therapy included strengthening exercises for the rotator cuff and scapular stabilizers. Relative rest consisted of 3 weeks of easy swimming below the pain threshold, with kickboard pool workouts and biking to maintain aerobic fitness.
We also referred her to a collegiate swimming coach who evaluated her technique and helped modify her workout plan.
He instructed her to carefully warm up and stretch before each workout. She progressed back into regular workouts slowly and was instructed to maintain her training with less overall yardage using interval training and regular rest periods (table 1: not shown). The coach taught her how to modify her stroke to lessen impingement by keeping the elbow lower during the recovery phase and by not crossing the midline with her hand during the pull-through phase of her stroke. After the above period of relative rest and 3 more weeks of gradually increasing workouts, the patient raced the last 2 months of the season, recording personal best times despite training with less overall yardage.
Understanding Swim Stresses
Swimming repeatedly stresses the complex shoulder joint. The shoulder's range of motion in multiple directions requires a degree of instability and little bony support. For stability, the shoulder relies on the capsule, the rotator cuff muscles, and the larger surrounding muscles such as the pectoralis major, the deltoids, the serratus anterior, and long head of the biceps. The scapula, though mobile, is the base of the glenohumeral joint and must be controlled for proper shoulder function. The rhomboids, serratus anterior, and trapezius muscles are the main scapular stabilizers in swimming (figure 1).
Impingement occurs when the soft tissues of the subacromial space are compressed between the head of the humerus and the coracoacromial arch and anterior acromion (6). The subacromial tissues include the supraspinatus tendon, the tendon of the long head of the biceps, and the subacromial bursa (figure 2). As these tissues become inflamed, the narrow space becomes even tighter, worsening the impingement.
Swimming brings the shoulder through at least one impingement position with each stroke. A 10,000-yd training session may include 4,000 or more strokes with each arm, probably the most overhead arm strokes used in any sport (5,7). The freestyle stroke consists of a pull-through phase while the arm is in the water, which provides propulsion, and a recovery phase in which the arm is above the water (figure 3). In this stroke, which most swimmers use for the majority of training, the shoulder is subject to impingement when the shoulder is in the early to mid pull-through phase (8), which involves extreme adduction and internal rotation. The extremely abducted arc of the recovery phase also produces impingement (9), as the humeral head is brought against the lateral acromion.
Rotator cuff fatigue, scapular dysfunction, and shoulder laxity can contribute to impingement syndrome. The rotator cuff holds the humeral head in position and depressed against the forces of other muscles, preventing its anterior and superior translation. Fatigue of the rotator cuff, then, allows impingement to worsen (8,10). Swimmers who have multidirectional laxity may also have more translation, compounding the impingement (1,11). When the muscles that anchor the scapula are overused, especially the serratus anterior, impingement can worsen because of a downward tilt of the scapula (9). In addition, the impinged area of the supraspinatus tendon is poorly vascularized, and the adduction and internal rotation at the end of the pull-through phase may contribute to tendinitis by compressing the tendon's vascular supply (3,4,12).
Inflexibility in the shoulders and anterior chest wall could indicate a strength imbalance as was seen in the patient in the case report; the slouched posture observed during her examination suggested a tight anterior chest wall and a strength imbalance. Weight training has classically focused on the anterior chest wall and internal rotators, while the external rotators and supportive muscles may be underdeveloped and unable to stabilize the shoulder. Greipp13 found that impingement pain increases in swimmers who increase the intensity and duration of weight training and in those who have less flexibility in the shoulder musculature.
Are Young People's Injuries Different?
Children naturally avoid activities that cause soreness and discomfort, but they are pushed beyond discomfort in competitive athletics when they have the motivation to succeed and pressure to please coaches and parents. Though swimmer's shoulder is seen in both adults and young people, the incidence is increasing in young swimmers as the intensity, length of practices, and the duration of the season increase (14). In addition, the syndrome may become worse because of adolescents' relatively underdeveloped shoulder musculature, increased laxity about the shoulder joint, articular softness, and bone immaturity (14-16). The sites of growth cartilage-the joint surface, the epiphyseal plate, and the apophysis-are susceptible to injury and may be involved in symptomatic young athletes. Often the physician will not become aware of the problem until the patient's symptoms interfere with practice and performance (17), and a complete assessment is vital.
Making the Diagnosis
The diagnosis of swimmer's shoulder is usually not difficult. Classically, the patient complains of pain in the anterior shoulder during or after swimming. It may interfere with the stroke or be associated with a certain phase of the stroke, although early in the course the discomfort may be present only after swimming. It is helpful to determine the strokes used, the usual distance swum, and the intensity of the training. History of other injury or dislocation may help determine any contributing factors.
The shoulder exam should include inspection, palpation, and testing of passive and active range of motion, strength, instability, and impingement. It is vital to completely examine both shoulders as well as the neck and elbows. Inspection of posture, muscle groups, and bones for asymmetry will help evaluate atrophy, muscle imbalance, and evidence of traumatic injury. Palpation of the supraspinatus tendon and the tendon of the long head of the biceps will help pinpoint tendinitis. Instability testing should include the apprehension test. Impingement can be elicited by the classic painful arc from 60° to 120° of abduction, especially with the arm internally rotated, plus other impingement tests.
Radiographs should include the anteroposterior view with the arm in external rotation, outlet view with 10° caudal angulation, and the axillary view.
The swimmer's form should be closely assessed for abnormal mechanics. It is useful to consult an experienced coach to assess and correct form.
The differential diagnosis for swimmer's shoulder includes labral damage, subluxation, rotator cuff tear, and, in young athletes, stress fracture of the proximal humeral physis (Little League shoulder) and apophyseal injury (18). These injuries may coexist with impingement and should be looked for in the evaluation of a swimmer with shoulder pain.
Target the Source of the Problem
The mainstay of treatment for overuse injuries is relative rest and activity modification, and swimmer's shoulder is no exception. Frequent icing and use of anti-inflammatory medications may speed healing. A period of relative rest or activity below the pain threshold should be recommended to allow healing and decrease inflammation. When prescribing relative rest, alternative activities should be suggested to prevent deconditioning. Fitness can be maintained with activities that do not stress the injured area. It is also appropriate to prescribe physical therapy and rehabilitation to guide strengthening and stretching programs.
Allegrucci et al (5) nicely outline specific modalities and phases of the physical therapy useful in the rehabilitation of patients who have swimmer's shoulder. Treatment focuses on correcting any imbalances in muscle strength and flexibility. In the patient described above, strengthening the rotator cuff and scapular stabilizers helped restore glenohumeral stability and allowed a more rapid return to activity. Subacromial injections have been used in the treatment of swimmer's shoulder, but they should be reserved for severe cases that do not respond to conservative treatment (9).
Swimmer's shoulder is a common problem that can restrict a swimmer's season. Prevention of this overuse syndrome is much easier than treating it midseason. Stretching and controlled warm-ups should be stressed in swimming programs at all levels. Strength training should emphasize external rotator development in the preseason.
As physicians, it is important that we encourage knowledge of overuse injuries and work with other professionals to develop alternative training techniques and to discourage overtraining.
Dr Koehler is a first-year family practice resident at Oregon Health Sciences University in Portland, Oregon, and Dr Thorson is a family practice physician at MinnHealth Family Physicians in White Bear Lake, Minnesota. Address correspondence to Scott M. Koehler, MD, 1430 Oregon Health Sciences University, Gabriel Park Clinic, 4411 SW Vermont St, Portland, OR 97219; e-mail to [email protected].
The authors thank William O. Roberts, MD, and David B. Haugland, MD, for their advice on this manuscript and Thomas A. Hodgson, EdD, for his biomechanical and coaching perspectives.