Shoulder pain is common with anywhere between 7 to 26% of the general population suffering from shoulder pain at a particular time point and up to 67% of the population having an episode of shoulder pain at least once during their life.
The shoulder joint (glenohumeral joint) is a joint between the glenoid of the scapula (shoulder blade) and the head of the humerus (arm bone). Shoulder pain can come from an injury to the glenohumeral joint but it can also come from an injury to the acromioclavicular (AC) joint (the joint between the acromion of the scapula and the clavicle (collarbone)). Shoulder pain can also be caused by impingement of structures between the glenohumeral joint and the acromion or from pain referred from the neck.
There are many structures associated with the shoulder joint that can be injured and cause pain. The most common of these are the rotator cuff tendons. The rotator cuff is a group of 4 muscles that run between the scapula and the humerus to help stabilise the shoulder joint. The 4 muscles are subscapularis, supraspinatus, infraspinatus and teres minor. The term rotator cuff tear is often used but most commonly this means a tear of the supraspinatus tendon.
The other structures that can be injured in the shoulder joint include the labrum, the capsule and the long head of biceps tendon. The labrum is a band of fibrous connective tissue that surrounds the socket of the shoulder joint (the glenoid) to make it deeper. It can be injured during a traumatic dislocation. The capsule of the shoulder joint can be affected by a condition called frozen shoulder (adhesive capsulitis) where it gets thicker and causes stiffness and pain. As with any other joint, the shoulder can also be affected by osteoarthritis.
Rotator cuff dysfunction
Rotator cuff dysfunction is the most common cause of shoulder pain in the general community. It is a spectrum of conditions that ranges from impingement pain due to dysfunction of the tendons acting as secondary stabilisers of the joint to full thickness tears of the supraspinatus tendon (plus or minus the other tendons). The resultant shoulder pain is due to a combination of factors including altered biomechanics of the shoulder joint complex (abnormal scapulohumeral rhythm) and pain arising directly from the injured structures themselves. The subacromial bursa is often implicated in shoulder pain but the existence of bursitis on imaging can be due to underlying pathology in the rotator cuff tendons rather than the bursa being the cause of the problem as previously thought.
Not all injured rotator cuff tendons cause pain and just because a tear is seen in a rotator cuff tendon on imaging doesn’t mean that it needs to be fixed. Degenerative wear and tear of the tendons is common with advancing age, especially in manual workers and there are many people with no shoulder pain at all that have rotator cuff tendon tears on MRI when performed for research. The percentage of asymptomatic tears in the population increases with each decade of life with 50% of 50 year olds with no shoulder pain found to have tears, increasing to 60% of 60 years olds and so on.
Acute, full thickness rotator cuff tears in young manual workers or athletes are best treated with surgical repair but there is scope for trying non-operative management in chronic tears in older people and for management of all other forms of rotator cuff dysfunction. This is one instance when it is very important to assess and treat the clinical signs in the person rather than what is found on imaging. A full thickness rotator cuff tear will not heal but with appropriate rehabilitation of the shoulder joint complex, full pain free range of motion and strength can be achieved leading to good functional outcomes. Sometimes injections are needed to help the rehabilitation process. Rotator cuff tears are very rare in people under 30 years of age.
There are two types of dislocations that occur in the shoulder joint, those that occur during trauma to the shoulder (acute, traumatic dislocation) and those that occur due to generalized laxity of the shoulder joint capsule making it easy for the shoulder to pop in and out (generalized multidirectional instability).
Acute, traumatic dislocations usually result in the labrum (a fibrous reinforcement of the glenoid (socket part) of the shoulder joint) being torn. This is known as a Bankart tear if it’s at the front of the joint and a SLAP tear if it’s at the top of the joint. The chance of having a second dislocation after the initial dislocation is as high as 70%, even after an adequate rehabilitation program and this rises to 90% after a second dislocation of the same joint. The labrum will not heal after injury but rehabilitation can be used to strengthen the rotator cuff muscles sufficiently to provide extra stability and keep the humeral head (ball of the joint) centered in the glenoid (socket) during activity. Many people regain full pain free function of the shoulder after non-operative management of a traumatic shoulder dislocation. If the injury is in an athlete who plays contact sport or requires the upper body for weight bearing (such as a gymnast) then surgical reconstruction should be considered to reduce the risk of ongoing dislocations, which in itself is a risk factor for osteoarthritis of the shoulder. A comprehensive rehabilitation program is needed after surgery and the athlete is usually out of sport for 6 months.
Multidirectional instability occurs in people who are generally flexible and have loose ligaments and joints. People sometimes use the term double jointed but this is a misnomer. Shoulder dislocation in multidirectional instability tends to affect adolescents and young adults. They can often pop their shoulders in and out quite easily without much pain. This is not good to do, however, due to the long-term risk of osteoarthritis. Management of this condition should be non-operative initially, with a comprehensive rehabilitation program aimed at strengthening the rotator cuff muscles to add extra stability to the joint. Surgery is best avoided if possible, especially in young people as reinjury rates after surgery are high and the substance of the capsule is often thin or loose as opposed to torn and therefore not ideal for surgical repair.
Frozen shoulder (adhesive capsulitis) is a condition that is unique to the shoulder joint. It can occur after trauma or surgery or it can develop insidiously with no precipitating cause. The condition involves progressively increasing stiffness in the shoulder joint and shoulder pain that can be mild compared to the level of stiffness or severe, unremitting and a cause of great distress. The condition is more common in diabetics but despite lots of research in the area, the cause is still unknown.
Adhesive capsulitis is a diagnosis of exclusion and the most common cause of shoulder joint stiffness after ruling out osteoarthritis of the joint. It can cause functional problems due to the inability to reach overhead and behind the back due to severely limited range of motion as well as causing significant pain both during activity and at rest. The condition is self-limiting and usually resolves on its own after 1 -2 years. One positive is that once it has resolved, it’s extremely rare to get it again in the same shoulder, however people who have had a frozen shoulder on one side are at increased risk of getting it in the other shoulder compared to the general population. There are management options to help with pain and shorten the duration of symptoms including oral analgesia, intraarticular injections, hydrodilatation, and capsular release surgery. Aggressive physiotherapy may worsen the symptoms initially and is best used after surgical management and when the joint is “thawing” and the range of motion starts to improve.
Acromioclavicular (AC) joint injury
Injury to the AC joint is a common cause of shoulder pain, especially after a fall onto the point of the shoulder. Pain from an AC joint injury is usually felt directly over the joint at the front of the shoulder and the joint is very tender to touch. If there is a separation injury, there may be an obvious lump or deformity of the shoulder seen. AC joint injury can also develop as an overuse injury without an obvious precipitating cause. It is common in sports such as power lifting or weights training for sports conditioning programs during bench press and in any activities that involve moving the arm across the body.
Special x-ray views can be used to diagnose AC joint injury in combination with clinical examination and advanced imaging is rarely needed. Most AC joint injuries can be treated symptomatically with reduction of aggravating activities and a comprehensive rehabilitation program. Surgical management is not usually indicated without trying non-operative management first and surgery doesn’t always have favourable outcomes. Sometimes injections are needed to help with the rehabilitation process.
If you have sustained a shoulder injury that has resulted in significant pain or dysfunction, or you can no longer participate in your preferred sport, leisure activity or work due to shoulder pain, a consultation at Shire Sports Medicine can be beneficial for you to get an accurate diagnosis, to help guide management of your condition and to ensure the prevention of further complications.