The shoulder is a complex and highly unstable joint, held in place by a system of muscles, tendons and ligaments. Shoulder pain causes can involve any part of this system and can be due to trauma, wear and tear or disease. Shoulder pain may also originate from elsewhere in the body as a referred pain. Understanding the major shoulder pain causes is crucial for accurate diagnosis of the underlying problem and effective treatment.
This article on shoulder pain is by Kathryn Senior, a freelance journalist who writes health, medical, biological, and pharmaceutical articles for national and international journals, newsletters and web sites.
Why are there so many shoulder pain causes?
The shoulder is the most flexible of all the joints but with flexibility comes instability. Unlike the hip, where the ball and socket match well, the ball of the shoulder joint is larger than the socket and so needs an array of tendons, ligaments and muscles to hold it in place.
Shoulder pain causes can include problems with any part of this complex connective tissue system, as well as problems with the bones themselves. Other shoulder pain causes are trauma – such as dislocations and muscle tears, wear and tear – such as impingement syndrome, or disease – such as tendonitis and arthritis.
Diagnosing the causes
Your GP will be able to get a fair idea of your shoulder pain causes by performing a simple examination and asking you a few questions. The type of pain, the circumstances in which it occurs, the appearance of the shoulder and the timescale over which it developed, will all give a good indication of what the pain is due to. Sometimes, an X-ray or MRI scan may be needed to back up the initial diagnosis and occasionally investigation via keyhole surgery is required.
Causes: rotator cuff problems
One of the most common shoulder pain causes is a problem with the group of four muscles called the rotator cuff. These muscles (the supraspinatus, infraspinatus, teres minor and subscapularis) stabilise the shoulder at the back of the joint, allowing for a wide variety of different movements.
Rotator cuff injuries cover any strain or damage to this group of muscles and tendons and fall into three main categories:
- Acute tear – where the muscles are damaged by a sudden trauma, such as a fall or a strenuous lift. In this case, the muscle is literally torn in one incident.
- Chronic tear – where the muscles become worn out and torn through repetitive use, such as in sports or jobs involving repeated stretching. In this case, the tear develops over time, gradually increasing in severity.
- Tendonitis – where the tendons around the rotator cuff become inflamed as a result of repeated use or the onset of old age. There is no tear involved, but the inflammation and swelling are the main shoulder pain causes.
Causes: frozen shoulder
Frozen shoulder, or adhesive capsulitis, is another of the more common shoulder pain causes, especially in women aged 40 to 60. As the name suggests, frozen shoulder is a severe restriction in movement of the shoulder joint. This can develop slowly, taking many months, with a steady decline in flexibility and movement causing a vicious circle of degeneration. Shoulder pain causes the joint to be underused and this lack of movement causes adhesions between the ball joint and the socket. This causes further swelling of the joint and tightening of the surrounding tissue, causing more pain and even less use. While the cause of frozen shoulder is unknown, diabetics are between two and four times at risk of developing it.
The most common of all shoulder pain causes is dislocation. This occurs when the humerus is forced out of the socket by either a strong pull or an extreme rotation, leaving the arm out of position and causing severe pain. However, dislocation can also happen without trauma, as the humerus gradually moves out of place as a result of repetitive exercise, such as swimming or energetic throwing.
In either case, the main treatment is to manipulate the shoulder back into place physically, a process called reduction. The shoulder then needs to be immobilized for up to six weeks to allow for full recovery of damaged muscles, tendons and ligaments.
As well as the main shoulder pain causes discussed above, there are many other, less frequent reasons for shoulder discomfort. These include:
- Osteoarthritis – the cartilage in the shoulder joint wears down
- Rheumatoid arthritis – this causes inflammation of the surrounding tissues
- Bursitis – inflammation of the bursa similar to tendonitis
- Impingement syndrome – where tendons become trapped in the shoulder joint
- Glenoid labrum injury – in which the lining of the socket becomes damaged
- Clavicle (collar bone) problems – including fractures and muscle tears
Causes: referred pain
Sometimes, the shoulder pain causes identified are nothing to do with the shoulder at all. Referred pain, as it is called, occurs as a result of misdirected nerve impulses from the true site of the injury. These shoulder pain causes can have origins in the cervical and thoracic spine as well as the gall bladder, liver or heart.
Treating the causes
The human body has an amazing capacity to heal itself, and the vast majority of shoulder pain causes are treated by a combination of rest and carefully structured exercises or physiotherapy. Initially, the shoulder is rested completely, using a sling or specialist shoulder immobiliser, to allow the muscles, tendons and ligaments to repair. This rest may be complemented by the application of heat or ice to reduce inflammation, along with anti-inflammatory painkillers, such as ibuprofen. Physiotherapy, or simple home exercises are then introduced to rehabilitate the shoulder.
In some cases, surgery may be required to repair torn muscles (rotator cuff injury) or to remove damaged or unwanted tissue (frozen shoulder) but this is usually only needed in severe cases and even then can be done as key-hole surgery.