It involves the rotator cuff tendon – a tough, rubbery cord that connects the muscles in the shoulder to the top of the arm. The tendon and muscle run through a narrow space at the top of the shoulder called the subacromial space.
In shoulder impingement syndrome, the tendon becomes trapped in this space and repeatedly scrapes against the bone above, causing pain that tends to be worse when the arm is raised overhead.
A persistent ache in the shoulder and pain at night may also be experienced.
Shoulder impingement syndrome can start suddenly after an injury, or (generally from middle age onwards) it can come on gradually without any obvious cause.
The subacromial space is naturally quite narrow, especially when the arm is raised. Anything that further narrows this space can cause the tendon to become trapped.
Possible causes include:
- bone spurs under the bony roof (acromion) at the top of the subacromial space can narrow the space and catch on the tendon
- swelling or thickening of the rotator cuff tendon – which may result from an injury or general overuse of the shoulder
- inflammation of the fluid-filled sac (bursa) that lies between the rotator cuff tendon and acromion (known as “bursitis”)
- a build-up of calcium deposits within the rotator cuff tendon
Signs & Symptoms
- Symptoms usually start gradually, in the top-outer portion of the shoulder
- There may be mild pain all the time, with sudden pain when reaching overhead and pain when lowering the arm from an overhead position
- There may be weakness of the shoulder
- If not treated, the condition may worsen
The supraspinatus outlet view may show anteroinferior acromial bone spur.
Rest shoulder and avoid activities that cause pain. Other measures include:
- Ice packs applied 20 minutes at a time, 3 to 4 times a day to the shoulder (protect the skin by wrapping the ice pack in a clean towel before applying)
- Taking medication, such as ibuprofen and naproxen, to help reduce swelling and pain
- Avoiding or reducing activities that cause or worsen symptoms
- Physical therapy to stretch and strengthen the shoulder muscles
- Medicine (corticosteroid) injected into the shoulder to reduce pain and swelling
If the treatments above aren’t effective, a surgery may be needed to widen the subacromial space in the shoulder, so the rotator cuff tendon is no longer rubbing against the bone above. This is known as subacromial decompression.
This can usually be done using a technique called arthroscopy, which is a type of keyhole surgery carried out under general anaesthetic, where special surgical instruments and a thin, flexible tube containing a camera are inserted through small cuts in the skin.
This means faster recovery and with less scarring than if a larger cut was made. Most people are able to go home the same day or the day after.