Impingement is a term that is frequently used. It comes from English and essentially means “pinching” or “compression”. The space between the humeral head and the acromion contains tendons that are essential for shoulder movement and function. It also contains a bursa (subacromial bursa), which acts as a cushion that allows the tendons to glide smoothly over the bone.

The anatomical characteristics of the acromion and humerus, including their shape and structure, are important factors in determining whether a person is predisposed to shoulder impingement syndrome. The humerus has bony prominences, the greater and lesser tuberosities (tuberculum majus and tuberculum minus), where the tendons of the rotator cuff attach.

During certain movements, these structures can come into contact with the acromion, causing the tendons and bursa to become pinched. This space can become narrowed for various reasons, such as bony changes or the condition of the tendons, which can interfere with the smooth gliding of these structures. As a result, the soft tissues become compressed and chronically irritated by movement, which can lead to inflammation of the bursa (bursitis) and, in severe cases, even partial tendon tears.

For example, wearing thick ski socks in tight-fitting shoes can eventually cause blisters or irritation. The same principle applies to the bursa when it is repeatedly compressed over a prolonged period.

Many people with shoulder impingement syndrome experience pain mainly in the lateral shoulder and upper arm, which may radiate toward the elbow and forearm during overhead activities and certain movements.

During inward and backward rotation of the arm, such as when reaching behind from the driver’s seat of a car, impingement or pinching may occur. Strength is usually not affected.

When the arm is raised to the side, restricted movement and significant pain may occur between 60° and 120°. This may be accompanied by a sensation of friction or grinding sounds. Movement below 60° and above 120° is usually no longer painful.

X-rays are used to assess the morphology and anatomy of the acromion. This allows us to determine the shape of the acromion, such as flat, curved, or hooked. It is important to note that the critical shoulder angle (CSA), which can be measured on an X-ray, provides information about the angle between the glenoid and the acromion. This angle may indicate whether a patient is predisposed to impingement and, among other conditions, rotator cuff tears. Another measurement is the Greater Tuberosity Angle (GTA), which assesses the degree of lateral extension of the humeral head.

As this is a soft-tissue condition, ultrasound can provide valuable information about the underlying cause of the symptoms. A clear sign of bursitis is a fluid collection in the subacromial space, which can be seen on ultrasound. There is also a bursa beneath the deltoid muscle, which can be visualized using ultrasound.

Ultrasound is often performed dynamically, meaning that the patient is asked to move the arm during the examination. This allows the examiner to directly identify whether soft tissue impingement is present and determine exactly where the problem is. An MRI can also reveal increased fluid accumulation, which may indicate bursitis.

As a first-line non-surgical treatment, NSAIDs (non-steroidal anti-inflammatory drugs) may be prescribed. These medications are used to relieve pain and reduce inflammation. They can be taken at a higher dose for 10 to 14 days to help break the cycle, as inflammation can lead to swelling and further narrowing of the space.

If treatment with NSAIDs does not provide sufficient relief, corticosteroid injections may be administered to the affected area. Physiotherapy can be initiated alongside medication. Glenohumeral centering exercises are commonly used as part of the treatment.

Glenohumeral centering exercises aim to keep the humeral head properly positioned without allowing it to migrate upward and come into contact with the acromion.

If neither medication nor physiotherapy provides sufficient relief, minimally invasive arthroscopic surgery may be considered. During the procedure, the inflamed bursa and surrounding inflamed tissue are removed, and the part of the acromion responsible for the impingement is reshaped (acromioplasty). This enlarges the space and prevents the bones from coming into contact with each other.