Shoulder instability is a common pathology encountered in the orthopedic and sports medicine setting. But “shoulder instability” itself isn’t that simple to understand. There exists a wide range of symptomatic shoulder instabilities from subtle recurrent subluxations to traumatic dislocations. Nonoperative rehabilitation is commonly utilized for shoulder instability to regain previous functional activities through specific strengthening exercises, dynamic stabilization drills, neuromuscular training, proprioception drills, scapular muscle strengthening program and a gradual return to their desired activities.
Because there are so many different variations of shoulder instability, it is extremely important to understand several factors that will impact the rehabilitation program. This will allow us to individualize programs and enhance recovery. There are 6 main factors that I consider when designing my rehabilitation programs for nonoperative shoulder instability rehabilitation.
Factor #1 – Chronicity of Shoulder Instability
The first factor to consider in the rehabilitation of a patient with shoulder instability is the onset of the pathology. Pathological shoulder instability may result from an acute, traumatic event or chronic, recurrent instability. The goal of the rehabilitation program may vary greatly based on the onset and mechanism of injury. Following a traumatic subluxation or dislocation, the patient typically presents with significant tissue trauma, pain and apprehension. The patient who has sustained a dislocation often exhibits more pain due to muscle spasm than a patient who has subluxed their shoulder. Furthermore, a first time episode of dislocation is generally more painful than the repeat event. Rehabilitation will be progressed based on the patient’s symptoms with emphasis on early controlled range of motion, reduction of muscle spasms and guarding and relief of pain.
Conversely, a patient presenting with atraumatic instability often presents with a history of repetitive injuries and symptomatic complaints. Often the patient does not complain of a single instability episode but rather a feeling of shoulder laxity or an inability to perform specific tasks. Rehabilitation for this patient should focus on early proprioception training, dynamic stabilization drills, neuromuscular control, scapular muscle exercises and muscle strengthening exercises to enhance dynamic stability due to the unique characteristic of excessive capsular laxity and capsular redundancy in this type of patient.
The primary traumatic dislocation is most often treated conservatively with immobilization in a sling and early controlled passive range of motion (PROM) exercises especially with first time dislocations. The incidence of recurrent dislocation ranges from 17-96% with a mean of 67% in patient populations between the ages of 21-30 years old. Therefore, the rehabilitation program should progress cautiously in young athletic individuals. It should be noted that Hovelius et al has demonstrated that the rate of recurrent dislocations is based on the patient’s age and not affected by the length of post-injury immobilization. Individuals between the ages of 19 and 29 years are the most likely to experience multiple episodes of instability. Hovelius et al also noted patients in their 20’s exhibited a recurrence rate of 60% whereas patients in their 30’s to 40’s had less than a 20% recurrence rate. In adolescents, the recurrence rate is as high as 92% (37) and 100% with an open physes (31)
Chronic subluxations, as seen in the atraumatic, unstable shoulder may be treated more aggressively due to the lack of acute tissue damage and less muscular guarding and inflammation. Rotator cuff and periscapular strengthening activities should be initiated while ROM exercises are progressed. Caution is placed on avoiding excessive stretching of the joint capsule through aggressive ROM activities. The goal is to enhance strength, proprioception, dynamic stability and neuromuscular control especially in the specific points of motion or direction which results in instability complaints.
Factor #2 – Degree of Shoulder Instability
The second factor is the degree of instability present in the patient and its effect on their function. Varying degrees of shoulder instability exist such as a subtle subluxation or gross instability. The term subluxation refers to the complete separation of the articular surfaces with spontaneous reduction. Conversely, a dislocation is a complete separation of the articular surfaces and requires a specific movement or manual reduction to relocate the joint. This will result in underlying capsular tissue trauma. Thus, with shoulder dislocations the degree of trauma to the glenohumeral joint’s soft tissue is much more extensive. Speer et al (49) has reported that in order for a shoulder dislocation to occur, a Bankart lesion must be present and also soft tissue trauma must be present on both sides of the glenohumeral joint capsule.
Thus, in the situation of an acute traumatic dislocation, the anterior capsule may be avulsed off the glenoid (this is called a Bankart lesion – see pictures to the right) and the posterior capsule may be stretched, allowing the humeral head to dislocate. This has been referred to as the “circle stability concept.” The rate of progression will vary based upon the degree of instability and persistence of symptoms. For example, a patient with mild subluxations and muscle guarding may initially tolerate strengthening exercises and neuromuscular control drills more than a patient with a significant amount of muscular guarding.
Factor #3 – Concomitant Pathology
The third factor involves considering other tissues that may have been affected and the premorbid status of the tissue. As we previously discussed, disruption of the anterior capsulolabral complex from the glenoid commonly occurs during a traumatic injury resulting in an anterior Bankart lesion. But other tissues may also be involved. Often osseous lesions may be present such as a concomitant Hill Sach’s lesion caused by an impaction of the posterolateral aspect of the humeral head as it compresses against the anterior glenoid rim during relocation. This has been reported in up to 80% of dislocations. Conversely, a reverse Hill Sach’s lesion may be present on the anterior aspect of the humeral head due to a posterior dislocation.
Occasionally, a bone bruise may be present in individuals who have sustained a shoulder dislocation as well as pathology to the rotator cuff. In rare cases of extreme trauma, the brachial plexus may become involved as well. Other common injuries in the unstable shoulder may involve the superior labrum ( SLAP lesion ) such as a type V SLAP lesion characterized by a Bankart lesion of the anterior capsule extending into the anterior superior labrum. These concomitant lesions will affect the rehabilitation significantly in order to protect the healing tissue.
These 3 key factors is really just the tip of the iceberg. For more information and detailed information on how these factors impact our rehabilitation programs, check out my online CEU program on the Recent Advances in the Evidence Based Evaluation and Treatment of the Shoulder . There is an entire week of content dedicated to shoulder instability that takes these keys even further.
Stay tuned for Part 2 next week, where we talk about the direction of instability and more factors to consider for nonoperative shoulder instability rehabilitation.