Shoulder  >  Shoulder Conditions  >  Impingement

This is one of the most common causes of shoulder pain. Classically it causes pain in the upper arm just below the shoulder upon activity and especially when the arm is elevated forwards or to the side.


The deep tendons of the shoulder are called the rotator cuff tendons and consist of 4 tendons; supraspinatus, infraspinatus, teres minor and subscapularis. This group of tendons play a very important role in moving the shoulder and also stabilising the humeral head (head of the arm bone) in the socket whilst the shoulder moves. The supraspinatus tendon, which is the uppermost part of the rotator cuff passes under the shoulder tip (acromion bone) and the ligament which runs from the shoulder tip (coracoacromial ligament). The acromion and coraco-acromial ligament together from an arch under which the supraspinatus tendon runs. Between the tendon and the arch is a fluid filled cushion called the bursa. This bursa can become irritated and inflamed and the supraspinatus tendon can also become inflamed and swollen. If this space becomes narrowed then when the arm is elevated away from the side this tendon can be squashed under the arch which can cause pain, as well as further inflammation and swelling of the tendon which then in turn causes further discomfort. The top surface of the tendon can become frayed and in some cases the tendon can eventually develop a tear.


The ligament (coraco-acromial) running from the front of the acromion can become calcified and develop into a bone spur which reduces the space under which the supraspinatus passes.


Also the shape of the acromion (shoulder tip) can contribute to narrowing of the space and irritation of the tendon. The front part of the bone can have a downward slope which if significant can cause the tendon to rub against it causing further swelling and irritation of the tendon as it rubs on the bone when passing underneath it.

Patients may complain of the following symptoms:
Pain - this is usually felt in the upper arm and is worse on certain movements, e.g. stretching arm out in front of you, lifting arm away from side, reaching back to put seat belt on etc. Pain can worsen with certain activities, e.g. driving with hands held at 10 to 2 (easier if hands lowered to 20 to 4), ironing, cleaning windows etc.
Restricted movement - especially behind the back. Sometimes, due to the pain, patients find it difficult to lift the arm above shoulder height although this can be made a lot easier if you use the other arm to lift the painful one.
Night pain – the pain wakes you at night and you difficulty lying on the affected side
'Clicking' or 'catching' - you may feel a catch and hear a click as the tendon rubs against the bone
When you are examined in the clinic the clinical diagnosis of impingement can be made. Often an x-ray of the shoulder may be performed to exclude arthritis or calcium in the tendons as a potential other cause for the pain. Sometimes an ultrasound scan is arranged to check that there is no tear of the rotator cuff tendons.
Treatment of shoulder impingement usually starts with anti-inflammatory painkillers and physiotherapy. This can be complimented with one or more (max 3) subacromial steroid injections (injection into the bursa underneath the shoulder tip and above the tendon). In approximately 80% of cases this treatment will be sufficient to satisfactorily alleviate the patient's symptoms. In some patients their posture may be contributing to the problem and the physiotherapists can help you to correct this.
If these non-operative treatments fail, symptoms have been present for at least 6 months and are restricting your function then the next step is to consider surgery. In a keyhole (arthroscopic) operation the inflamed bursa can be removed and the undersurface of the acromion (shoulder tip) can be shaved away to excise the bone spur, flatten the curve on the undersurface of the acromion and thereby increase the space the supraspinatus tendon has to move in (effectively this raises the roof of the space). This reduces the irritation and compression on the inflamed painful tendon. This procedure is known as an Arthroscopic Subacromial Decompression (ASD).
The collar cone (clavicle) attaches to the shoulder tip (acromion) by a joint called the acromio-clavicular joint. If the acromio-clavicular joint (AC joint) is arthritic then this can also be a cause of shoulder pain. The first treatment is anti-inflammatory painkillers and occasionally a steroid injection is used. If these measures fail to control symptoms then the joint can be excised so the arthritic sides of the joint do not rub together causing pain. This joint can be excised arthroscopically (keyhole) and performed at the same time as the arthroscopic subacromial decompression.