Subacromial impingement

What is subacromial impingement?

Beneath the acromion there is a limited space containing the rotator cuff tendons and the subacromial-subdeltoid bursa. During arm elevation these structures move in relation to each other. Pain may develop when the tissues are irritated or when shoulder movement is poorly controlled.

Subacromial impingement is not always simply a problem of “too little space”. In some patients structural changes are more important, while in others impaired function of the rotator cuff, deltoid and scapular muscles contributes more strongly.

Typical symptoms

• pain when raising the arm, often in the middle range of elevation;
• pain with overhead or repetitive activities;
• pain when lying on the affected side;
• pain or weakness during abduction and rotation;
• sometimes night pain, particularly when the bursa is inflamed.

These symptoms are not specific to subacromial impingement. Similar symptoms can occur with rotator cuff tears, calcific tendinopathy, frozen shoulder, osteoarthritis, biceps tendon disorders or pain referred from the neck.

The role of the subacromial bursa — expand

The bursa reduces friction between tissues during movement. If inflamed and swollen, it may become an important source of pain itself. Increased bursal volume can also make shoulder elevation more uncomfortable.

If severe pain prevents effective rehabilitation, an orthopaedic surgeon may in selected cases consider a local corticosteroid injection into the bursa. The aim is to reduce pain and inflammation so that rehabilitation can proceed. An injection does not remove osteophytes and does not replace exercise therapy.

How is it diagnosed?

Diagnosis begins with history and clinical examination: range of motion, strength, symptoms during specific movements and the function of the scapula and rotator cuff. No single provocative test is sufficient by itself.

Imaging: X-ray, ultrasound and MRI — expand

X-ray

Useful for assessing bone morphology, osteophytes and degenerative changes in the acromioclavicular and glenohumeral joints.

Ultrasound

Useful for assessing the rotator cuff, bursa, long head of biceps tendon and calcific deposits, with selected structures also assessed dynamically.

MRI

May be helpful when more detailed assessment of the rotator cuff or other soft tissues is needed, particularly when imaging will affect surgical planning.

Nonsurgical treatment and rehabilitation

Appropriately selected rehabilitation is the mainstay of treatment. In functionally driven subacromial pain, the key goals are improved rotator cuff strength and control, better stabilisation of the humeral head and improved scapular function.

Exercise does not remove osteophytes or alter acromial shape, but it can improve shoulder function and reduce symptoms even when structural changes are present.

When may surgery be considered? — expand

Surgery should not be based solely on the presence of an osteophyte or the word “impingement” in an imaging report. The pattern of structural disease, loss of function, tendon status, response to well-conducted nonsurgical care and the patient’s functional goals all matter.

If substantial pain and functional limitation persist despite appropriate rehabilitation, the diagnosis and the reason for treatment failure should be reassessed before further decisions are made.