Shoulder instability has been, until recently, an under-recognized source of shoulder pain in individuals involved in repetitive or prolonged overhead activities in the workplace. Once thought to be unique to young (< 30 years of age) athletes involved in throwing, swimming, and racquet sports, shoulder instability is becoming a more frequently recognized factor in shoulder pain in industry. Despite the increased incidence of individuals having shoulder pain as a result of instability, many of these patients continue to be inappropriately diagnosed and treated for injuries associated with instability rather than for the primary problem.
Accurate diagnosis of individuals with shoulder instability begins with recognition of laxity of the glenohumeral joint. In the absence of a defined injury, the examiner must invoke clinical tests to detect the presence of laxity. These techniques provoke the glenohumeral joint in anterior, posterior, and inferior directions. The load and shift test, apprehension test, relocation test, and sulcus sign are often used for this purpose. Atraumatic laxity is often present in more than one direction, and occasionally in both shoulders. In this case, the instability is more specifically referred to as multi-directional instability (MDI). Instability in one direction most often occurs in the anterior or posterior direction.
If these individuals have inherent laxity in their shoulders, why do they become symptomatic without a defined injury? In the presence of prolonged or repeated movement of the arm that may also include lifting and holding of tools and other objects, the rotator cuff is required to make up for the lack of capsular stability. The result is overuse of the rotator cuff, manifested in symptoms of increasing pain and inflammation of the rotator cuff and capsule. It becomes evident when examining the individual with symptomatic instability that strength and coordination of movement of the shoulder is diminished. The rotator cuff and biceps tendon are often inflamed and tender to palpation.
Patients identified with atraumatic instability have historically responded favorably to conservative care. Interventions including anti-inflammatory medications, modalities for pain relief and anti-inflammatory purposes, activity modification, pain-free strengthening of the rotator cuff and scapular stabilizers, and functional integration activities are often cited mainstays of treatment.
Additionally, taping the involved shoulder to provide stability during the acute and sub-acute phases of rehabilitation will accelerate movement to the more aggressive strengthening that precedes returning to pain-free occupational demands. Application of tape is performed every 48 to 72 hours during the acute and sub-acute phases, and the frequency of application is decreased as strength increase and functional stability increases over time.
Several interventions that continue to be widely used have questionable roles in the treatment of patients with atraumatic instability. Strengthening with elastic bands, while convenient for their mobility and versatility, often serve to inflame tissues that are already irritable. Second, stretching of the shoulder joint beyond comfortable physiological limits has no place in the treatment of patients with shoulder instability. Finally, the use of non-specific strengthening modalities such as the UBE in the acute or sub-acute phases of rehab is inappropriate and possibly injurious.
Individuals with a traumatic onset of instability are less likely to have a favorable outcome with conservative intervention because of the increased prevalence of co-morbid conditions after injury. Bony pathology to the glenoid (Bankart lesion) or humeral head (Hill-Sach’s lesion), tears to the glenoid labrum (ie SLAP lesions), or injuries to the capsule present changes to normal anatomy that may prevent the restoration of full function. Surgical intervention to repair the abnormal anatomy and prevent subsequent episodes of instability may be the best intervention for these patients. However, in the presence of normal anatomy and a well conceived rehabilitation program, many patients are still able to achieve full function after subluxation or dislocation.
In conclusion, accurate diagnosis of individuals with shoulder pain and functional limitations due to glenohumeral instability is an important first step to successful rehabilitation and return to work. Patients with normal anatomy should be able to return to full function within a short period of time if appropriate intervention is offered. Conservative management including protection from re-injury, taping, pain-free strengthening, and anti-inflammatory care are all associated with successful outcomes. Early use of elastic bands, non-specific strengthening, or aggressive stretching have been noted to delay or prevent successful recovery.