Subacromial Impingement
What Is the Anatomy of the Subacromial Space?
The subacromial space is the area between the top of the humeral head (upper arm bone) and the underside of the acromion (part of the shoulder blade). This space contains important structures that allow smooth shoulder movement, including the supraspinatus tendon (part of the rotator cuff), the long head of the biceps tendon, and the subacromial bursa—a space between the tendons and bone. The space is normally small and can narrow further during shoulder elevation or repetitive overhead activities.
How Does Subacromial Impingement Occur?
Subacromial impingement occurs when the rotator cuff tendons or bursa become compressed within the subacromial space during shoulder movement. This can be caused by:
Repetitive overhead activities such as throwing, swimming, or lifting.
Irregular shape of the acromion that reduces the available space.
Weakness or poor coordination of the rotator cuff and scapular muscles leading to abnormal shoulder mechanics.
Inflammation or thickening of the bursa or tendons.
Over time, this repetitive pinching causes irritation, swelling, and degeneration of the tendons, resulting in pain and restricted motion.
What Is the Long-Term Consequence of Having Subacromial Impingement?
If left untreated, subacromial impingement can progress to:
Persistent shoulder pain, especially with overhead movements or reaching behind the back.
Night pain, particularly when lying on the affected side.
Weakness of the shoulder due to chronic inflammation or tendon damage.
Development of partial or full-thickness rotator cuff tears.
How Does Subacromial Impingement Get Diagnosed?
Diagnosis is based on a combination of clinical history, examination, and imaging:
History of shoulder pain during overhead activity or repetitive movement.
Physical examination findings: lateral shoulder pain with elevation of the shoulder.
X-rays to evaluate the shape of the acromion and rule out bone spurs or arthritis.
MRI to assess the condition of the rotator cuff tendons and subacromial bursa.
What are the indications for treating Subacromial Impingement Non-Operatively?
Non-operative treatment is appropriate in most cases, especially early in the disease process. It is recommended for:
Mild to moderate symptoms without significant tendon tearing.
Early inflammation or bursitis without mechanical obstruction.
Patients willing to participate in physiotherapy and modify aggravating activities.
Older or low-demand individuals who prefer to avoid surgery.
Treatment typically includes physiotherapy to strengthen the rotator cuff and scapular stabilisers, improve posture, and restore biomechanics. Other treatments may include anti-inflammatory medication, corticosteroid injections, and modification of activities that worsen symptoms.
What are the indications for treating Subacromial Impingement Operatively?
Surgical management may be considered when:
Symptoms persist despite 3–6 months of structured non-operative treatment.
There is evidence of significant tendon damage or bone spurs causing mechanical narrowing of the space.
Pain and weakness limit work, sport, or daily activities.
Conservative treatment fails to restore function or relieve pain.
Surgical options include arthroscopic subacromial decompression, where inflamed tissue and acromial spurs are removed to increase space for the tendons. In cases with associated rotator cuff tears, repair may also be performed at the same time to restore strength and stability.
