Subacromial Impingement Syndrome (SAIS)

Subacromial impingement syndrome (SAIS) refers to inflammation and irritation of the rotator cuff tendons as they pass through the subacromial space, resulting in pain, weakness, and reduced range of motion within the shoulder.

SAIS encompasses a range of pathology including rotator cuff tendinosis, subacromial bursitis, and calcific tendinitis. All these conditions result in inflammation between the coracoacromial arch and the supraspinatus tendon or subacromial bursa.

It occurs most commonly in patients under 25 years, typically in active individuals or in manual professions, and accounts for around 60% of all shoulder pain presentations, making it the most common pathology of the shoulder.

The main cause of the syndrome is the narrowing of the space (<7 mm) between the head of the humerus and the acromion, which leads to inflammation of the subacromial bursa and mechanical irritation of the rotator cuff tendons, which pass through this space. Pain mainly occurs during abduction (arm lifting sideways) and forward flexion (lifting arm forward) of the upper limb, due to impingement of the humeral head against the anterior / inferior surface of the acromion.

The shoulder joint (glenohumeral joint) is the most mobile but least stable joint in the human body. Unlike other joints, its stability is ensured primarily not by the bones, but by the ligaments and muscles of the surrounding area.

Four muscles with their tendons (supraspinatus, infraspinatus, subscapularis and teres minor) form the rotator cuff muscles. In combination with the strong ligaments of the area, they stabilize the large-diameter head of the humerus within the small articular surface of the glenoid cavity. Due to this complex structure within a very limited space, the shoulder joint is susceptible to conditions such as Subacromial Impingement Syndrome (SAIS) or dislocation.

Summary

• Subacromial Impingement Syndromeresults from narrowing of the space between the humerus and acromion.
• This causes inflammation and irritation of the subacromial bursa and rotator cuff tendons.
• The shoulder’s complex anatomy and reliance on soft tissues for stability make it prone to this condition.
• Symptoms are mostly pain during arm elevation movements.

At the early stage of the syndrome, symptoms are usually mild. Many patients don’t seek medical attention initially because pain can be controlled with over-the-counter painkillers and rest. The discomfort often comes on gradually.

Over time, the pain worsens and can become persistent, sometimes severe enough to interfere with sleep, especially when lying on the affected shoulder. The characteristic symptom of the Subacromial Impingement Syndrome (SAIS) is the painful limitation of active shoulder movement. This means patients may have trouble lifting or rotating their arm without pain. The pain typically is felt on the outer (lateral) aspect of the shoulder and can radiate down the upper arm to about the mid-arm level. Activities involving shoulder elevation (lifting the arm up) or abduction (moving the arm away from the body sideways) are especially painful.

Further diagnosis of the syndrome combines clinical evaluation and imaging:

1. Clinical Exam:

The doctor checks for pain during specific shoulder movements and tests muscle strength and range of motion.

2. Imaging Studies:

• X-rays (Conventional Radiology):

The X-rays can show bony changes such as a decreased space between the humeral head and the acromion (called the subacromial space). Narrowing here suggests mechanical compression of the tendons or bursa.

• Ultrasound:
  it is useful for visualizing soft tissues like the inflamed subacromial bursa and rotator cuff tendons. It can detect swelling, tears, or fluid buildup.
• MRI (Magnetic Resonance Imaging):

It offers detailed images of both bone and soft tissues. It helps assess the extent of inflammation, tendon damage, bursitis, and any other joint abnormalities. MRI is the most comprehensive diagnostic tool for this syndrome.

Conservative (Non-Surgical) treatment

The principle behind successful treatment of Subacromial Impingement Syndrome is early intervention. The sooner treatment starts, the better the chances of recovery and prevention of chronic damage. Early treatment helps reduce inflammation, prevent further injury, and restore shoulder function. It should be tailored to the severity and stage of the condition, with a focus on shoulder protection and avoiding aggravating movements. Treatment depends on how advanced the condition is (early irritation vs. more severe tendon damage) and how bad the symptoms are. Mild cases may just need rest and NSAIDs; more severe or persistent cases might need injections or physical therapy.

Patients should avoid activities that cause pain, especially raising the arm above shoulder level. This reduces mechanical irritation of the tendons and bursa.

Nonsteroidal anti-inflammatory drugs help reduce pain and inflammation. These are used for a limited duration because long-term use can cause side effects.

If pain and inflammation persist despite NSAIDs, corticosteroid injections can be administered directly into the subacromial space. These injections reduce inflammation quickly. However, injections should be limited to a maximum of three times to avoid tissue damage or weakening of tendons.

An important and critical part of conservative management of the syndrome is physical therapy that is focused on:

• Strengthening the rotator cuff muscles and scapular stabilizers (muscles around the shoulder blade).
• Improving shoulder joint mobility and flexibility.

Proper exercises can restore normal shoulder mechanics, reduce impingement, and prevent recurrence. A physical therapist will often design a gradual and specific exercise program tailored to the patient’s condition.

Additional Notes:

• If conservative treatments fail or if there is a rotator cuff tear or significant structural damage, surgical options may be considered.
• Treatment success depends heavily on patient compliance with movement restrictions, medication schedules, and physical therapy exercises.
• Educating patients about avoiding repetitive overhead activities or heavy lifting during recovery is essential.

Conservative treatment typically includes rest, anti-inflammatory medications, physical therapy, and corticosteroid injections aimed at reducing inflammation and pain.

If symptoms do not improve after adequate conservative management, surgical treatment may be considered.

The most appropriate surgical treatment of Subacromial Impingement Syndrome is shoulder arthroscopy. Through 2-3 small surgical incisions (<1 cm), the surgeon performs acromioplasty during which the underside of the acromion is reshaped to create a smoother, flatter surface. This removes any bone spurs or irregularities that contribute to impingement. At the same time, the surgeon also performs subacromial decompression that is the removal of the inflamed bursa (bursectomy) to reduce swelling and create more space in the subacromial area.

The goal of this surgery is to increase the subacromial space, preventing the rotator cuff tendons from getting pinched during arm movements. This reduces pain and improves shoulder function.

Arthroscopic surgery also allows the surgeon to inspect all shoulder structures — rotator cuff tendons, biceps tendon, labrum, cartilage — and treat any other issues found during the procedure.

Compared to open surgery, arthroscopy usually results in:

• Smaller scars
• Less postoperative pain
• Faster recovery time

The arthroscopic treatment of Subacromial Impingement Syndrome has a success rate exceeding 90%, meaning most patients experience significant pain relief and functional improvement.

Rehabilitation post-surgery typically includes physical therapy to restore strength and range of motion.