The subacromial bursa is a sac like structure that lies between the acromion (part of the shoulder blade/scapula) and the tendons of the rotator cuff. It is known to contain numerous nerve endings such that it is often implicated as a source of pain in a variety of shoulder conditions.
The tissue that makes up the bursa often has the appearance of being inflamed although it’s still uncertain as to whether the inflammation is due to a primary problem of the bursa itself or if it’s in response to an underlying shoulder condition, such as subacromial impingement or a rotator cuff tear. Because of this, the symptoms associated with bursitis are very similar to those of subacromial impingement and rotator cuff tears.
- Pain related to shoulder movement
- Night pain
- Restricted movement secondary to the progressive thickening and scarring of the bursa.
Causes & Risk factors
There are numerous causes of subacromial bursitis/ impingement, some of the more common ones include;
- The rotator cuff tendons; if the tendons become weak and painful due to an injury (tendonitis) or through degeneration (tendinosis) then they may not be strong enough to control the humeral head (ball). This weakness, or imbalance, can result in the inappropriate movement of the humeral head that in turn causes inflammation of the bursa, which might be further aggravated if the tendons rub against the bony acromion.
- A bone spur; a prominent thickening of the tip of the acromion can result in a bony spur forming. This can impinge / rub on the underlying tendons of the rotator cuff and cause inflammation and bursitis.
- Capsular restrictions; if the capsule of the joint should become inflamed (capsulitis) such as in a Frozen Shoulder, the abnormal movement which follows can result in muscular imbalances which results in rubbing between the tendons of the rotator cuff and the acromion. This in turn results in the inflammation that results in bursitis.
The diagnosis of bursitis is often made purely on clinical grounds. The mainstay of the diagnosis is to determine if there is any other significant underlying diagnosis which has resulted in the bursitis. Ultrasound scans and magnetic resonance imaging (MRI) can be used to shed more light on any underlying shoulder condition. These investigations can help with the diagnosis of related conditions such as calcific tendonitis and rotator cuff tears.
To confirm the diagnosis, local anaesthetic can be injected into the subacromial space. By bathing the inflamed bursa and rotator cuff tendons in local anaesthetic the pain caused by the inflammation should improve, thereby supporting the diagnosis.
There are a number of treatments available for bursitis however often more than one treatment modality is used to manage the symptoms. The options include;
- Conservative treatment; comprising of rest, activity modification and the use of anti-inflammatory medications.
- Physiotherapy; a physiotherapy based exercise regime to balance the rotator cuff and stabilising muscles of the shoulder can be used to help the bursal inflammation settle such that movement and pain improves. A stretching and strengthening exercise programme can then be used to improve the range of shoulder movement.
- Injection treatments; the space between the rotator cuff and the acromion (the subacromial space) can be injected with local anaesthetic and cortisol. The anti-inflammatory component of the injection can reduce the swelling and pain associated with bursitis. This is usually used in conjunction with physiotherapy to aid recovery.
- Arthroscopic subacromial bursectomy; if the inflammation and pain from the bursa is being caused by an underlying shoulder condition then surgery may be needed to address the shoulder pathology. The exact nature of the surgery will depend on the underlying diagnosis but if other treatment modalities have failed to improve the symptoms then surgery can be undertaken. This will usually involve a subacromial bursectomy and most probably an arthroscopic subacromial decompression. If necessary a rotator cuff repair may also have to be considered.