Shoulder Multidirectional Instability in Swimming Athletes
Jan. 4, 2006
James Dreese, MD, and Bryan C. Matson, ATC, M.Ed.
Competitive swimming requires demanding repetitive motions that subject the athlete to shoulder injuries. In a typical 2 hour pool training session, an elite level competitive swimmer may swim up to 4 miles, which equates to between 1,500 and 4,000 stroke cycles. It is no great surprise that shoulder pain afflicts a high number of swimmers. Studies have shown that up to 75% of swimmers have a history of shoulder pain that interfered with training or competition.
Many factors may contribute to shoulder pain in competitive swimmers. Females may be more predisposed because of a shorter arm stroke, and therefore the need to make more stroke cycles for a given distance. The experience level of the swimmer can contribute in that inexperienced amateur swimmers make less efficient strokes, and have a greater likelihood of injury as a result. Longer training distances expose swimmers to greater likelihood of injury. Choice of stroke may also place swimmers at increased risk for shoulder pain.
Numerous explanations exist regarding the cause of shoulder pain in swimmers. Most swimming strokes disproportionately strengthen the anterior chest wall and shoulder internal rotators. As a result the shoulder external rotators are underdeveloped, leading to a muscular imbalance and dynamic instability of the joint. This imbalance is seen in swimmers as early as the middle school and high school levels, and must receive special attention in the training regimen, or corrected via rehabilitation in the athletic training room or physical therapy. In addition, swimming strokes subject the shoulder to repetitive microtrauma that can ultimately lead to failure of the supporting structures. The shoulder joint consists of stabilizing forces that are both static and dynamic. Static stabilizers include the shoulder joint capsule and ligaments, concave shape of the shoulder joint, and articular cartilage of the humeral head. Dynamic stabilizers consist of the muscles of the shoulder, including the deltoid, rotator cuff, and scapular stabilizing muscles. The shoulder joint relies on both competent static and dynamic stabilizers to function properly. Shoulder pain may begin as the result of overuse fatigue in the rotator cuff. The dynamic stabilizers will fatigue, and become painful, when their strength and endurance thresholds have been exceeded. As a result the effectiveness of the dynamic stabilizers is compromised, placing more stress on the static stabilizers. With overuse the static stabilizers can progressively fail under the additional demands, leading to instability of the shoulder. A typical scenario is a swimmer who develops painful activity-related overuse symptoms in the rotator cuff, leading to fatigue with prolonged swimming activities. As the dynamic stabilizers fatigue the static stabilizers are placed under increasing stress. With continued stress the static stabilizers undergo progressive failure, leading to shoulder imbalance and instability.
It is important to note the difference between shoulder "laxity" and "instability." Laxity refers to a painless, asymptomatic joint that has increased range of motion. It is very common in competitive adolescent swimmers. The apparent increased motion is typically referred to as being "loose-jointed" or "double-jointed." In fact, it is hyper mobility that is often associated with elite swimmers, with the increased range of motion allowing the swimmer increased lever arm to pull and/or push water. An important distinction is that the increased range of motion in the setting of shoulder laxity is not painful. Athletes with shoulder laxity often exhibit signs of ligamentous laxity elsewhere in the body, such as hyperextension of the knees, fingers, and hand, and the ability to touch the thumb to the forearm. These signs, particularly hyperextension of the elbow, and the ability to touch the thumb to the forearm, are important signs that the athletic trainer should incorporate into their special tests when evaluating the swimmer with shoulder pain. Contrary to laxity, shoulder instability is a condition of painful, symptomatic increased range of motion. It can take the form of increased painful joint translation, referred to as subluxation, or a complete dislocation of the joint requiring relocation maneuvers in the emergency department. Instability can occur in just one direction (anterior, posterior, or inferior) or it can occur in more than one direction (multidirectional instability). Instability can further be classified as the result of a single, traumatic event or from repetitive microtraumatic stresses. Swimming strokes subject the shoulder to repetitive stress and, as a result, often lead to recurrent multidirectional subluxation. Detailed evaluation of the swimmers stroke mechanics may be performed via videotape or underwater windows such as those available in rehabilitation pools such as the SwimEx. Critical evaluation of the stroke cycle, arm position as it relates to the mid-line of the swimmers body during mid-stroke and follow through, may provide valuable information to mechanical factors that are contributing to the painful instability and to differentiate between multidirectional subluxation and other pathologies such as impingement.
Treatment for multidirectional instability is directed at strengthening the fatigued dynamic stabilizers. Initially, a period of activity modification and rest is often indicated. It is important to avoid painful arm positions that recreate the shoulder pain during this time and to utilize ice along with other pain relieving modalities such as electrical stim. Typically that means avoiding the impingement zone above 90 degrees of abduction. Rehabilitation protocols directed at restoring a normal, pain-free range of motion and strengthening the deltoid, rotator cuff, and scapular stabilizers are then instituted. The athletic trainer or physical therapist can utilize rotator cuff protocols such as The Throwers Ten to strengthen these muscle groups. Use of theraband, dumb bell weights, and manual resistance exercises are all good options for strengthening. The goal of the strengthening protocol is to return the agonist and antagonist muscles to their proper strength ratios. When the swimmer has regained a pain-free active range of motion and 90% of rotator cuff strength the return to functional swimming is begun. Early return to competition swimming can be done in a rehabilitation pool, when available. This allows the athletic trainer to observe stroke frequency, quality, arm and shoulder position, while being able to control current and duration of intervals. Swimming activity is progressively increased as tolerated in a pain-free fashion. Return to competitive swimming is allowed when the athlete can maintain proper shoulder mechanics despite a fatiguing workout. It has been estimated that 95% of swimmers are able to return to competitive swimming following a program of intensive rehabilitation. Close monitoring of the early days following return to team activities is essential. Careful oversight by the athletic trainer is essential in preventing reoccurrence of symptoms.
Surgery for multidirectional instability is considered only after a prolonged period of directed physical rehabilitation has failed. This is generally considered to be a 6 month period of time. Recently, arthroscopic surgical techniques have proven effective in treating multidirectional instability. Advantages of arthroscopic techniques include smaller incisions, the ability to detect additional injuries present in the shoulder joint, and the ability to perform the surgery without detaching the anterior rotator cuff muscle (subscapularis). Thermal-assisted capsular shrinkage surgery has proven to yield unreliable results with high failure rates and concern for its long-term effect on the capsular tissue. Regardless of the surgical technique chosen, return to competitive swimming is generally 6-9 months.