Shoulder pain is common. It is the third most common cause of musculoskeletal consultation in primary care. 1% of patients consult the GP each year with new shoulder pain and the self-reported prevalence of shoulder pain is between 16% and 26% that is to say 16% to 26% of adults of shoulder pain at any one time.
The most common cause of shoulder pain is from a group of four muscles and tendons called the rotator cuff.
About your Shoulder
The shoulder joint is predominantly a ball and socket joint, made up of the head of the humerus (the ball) and the glenoid part of the scapula (the socket).
Above the ball and socket joint is the roof of the shoulder made up of a bony and ligamentous arch (the acromion bone and coraco-acromial ligament)
The shoulder is moved by a complex arrangement of muscles.
Deep to the large outer deltoid muscle of the shoulder are found the rotator cuff muscles and tendons.
These muscles originate from the front, back and top of the shoulder blade and condense down to form an almost continuous sheet or cuff of tendons which attach to a bony ridge along the edge of the head of humerus.
This group of muscles and tendons known as the rotator cuff, help move the shoulder and control the position of the ball in the socket.
Over the top surface of the tendons lies a fluid filled lining (bursa) that helps the tendons glide under the arch of the shoulder as the arms is lifted towards and above shoulder height.
What is Impingement?
As the arm moves away from the body the rotator cuff tendons normally glide painlessly under the bone and ligament roof of the shoulder (coracoacromial arch) in a space called the subacromial space.
The rotator cuff tendons in particular the tendon over the top of the shoulder (supraspinatus) can cause pain as they move through the subacromial space under the arch of the shoulder.
This pain is called impingement pain.
What are the symptoms?
Impingement pain is characteristically felt over the outside of the upper arm. Classically the pain is worse as the arm is lifted away from the body particularly when the arm reaches shoulder height and above. The pain is often worse when putting on jackets or coats and with activity when the arm is used at or above shoulder height. It is often worse at night and wakes patients if the lie on the affected side.
Shoulder blade (scapula) pain, neck pain, forearm and hand pain associated with pins and needles or numbness often indicates the symptoms are coming from the neck rather than the shoulder.
Is it common?
About 1 in 5 people will experience the symptoms at some stage in their lives. It is most common in the 40-65 year old age group
Why does it happen?
There are many potential causes of rotator cuff impingement pain. The most common cause is due to age related degenerative wear and tear of the tendon. This wear and tear may be influenced by genetic and environmental factors. When this less healthy tendon passes under the roof of the shoulder with shoulder activity it can produce impingement pain.
Any condition influencing the space for the rotator cuff tendons can give rise to impingement pain, these may include, postural changes and muscle imbalance, over-activity, calcium deposits in the tendon, acute inflammation of the tendon or bursa, bony spurs, or acute traumatic tears to the tendon.
Will I need any tests done?
Frequently X-Rays are done, but commonly ultrasound scans and MRI scanning can be very useful and help diagnosis and treatment.
What treatment may be needed?
Only a small percentage of patients require surgery as most symptoms settle with non operative treatment.
Rest and Pain relief
Avoiding the activities that make the pain worse together with the use of simple pain killers such as anti-inflammatory tablets and paracetamol can often help at improving symptoms.
Physiotherapy can be very helpful. Balancing and stabilising the muscle pull around the shoulder together with strengthening the rotator cuff muscles can both statically and dynamically improve the space for the tendons to move and improve pain and function in the impinging shoulder. Referral to the specialist shoulder physiotherapist is likely as part of treatment.
Steroid or cortisone injections are often very helpful in the treatment of shoulder pain. They are given with local anaesthetic as an outpatient procedure, frequently using ultrasound guidance, in order to place the injection in exactly the right position. Injections can give good long term relief of symptoms. There are some risks to injection treatment including, a transient or poor response, occasionally the pain being made worse for 24-48 hours before improving over a few weeks, transient facial flushing and very small risks of infection. Steroid injections do carry a risk to the quality of tendons or cartilage, this risk is difficult to quantify so we try to keep the number of injections to a minimum.
If symptoms persist and are significant despite non operative treatment then surgery may be considered. This is most commonly in the form of a keyhole operation to create more space for the tendons to move called arthroscopic subacromial decompression.