The Shoulder - Subacromial Impingement

Subacromial impingement is the most common cause of shoulder pain accounting for 44-65% of all shoulder complaints.

Common in persons who play, or have played, repetitive overhead or throwing sports, and manual jobs requiring prolonged overhead positions of the arm, subacromial impingement results from inflammation and degeneration of anatomical structures in the region of the subacromial space, namely the rotator cuff tendons and the subacromial bursa. This irritation results in pain, weakness and loss of active range of motion of the shoulder.

Anatomy 101

The shoulder or glenohumeral joint is an unstable, shallow, ball and socket joint, often described as a golf ball (the head of the humerus) sitting on a tee (the glenoid socket). The joint requires both static and dynamic stabilisers for effective shoulder function. The static constraints include the glenohumeral ligaments, glenoid labrum, and the joint capsule, and the dynamic constraints include the rotator cuff and scapular muscles.

The subacromial space is the area between the acromion above and the head of the humerus below. It is occupied by the rotator cuff tendons (as they pass from the shoulder blade (scapula) to the upper arm (humerus)), and the subacromial bursa, a small sack of fluid that acts as a buffer between the tendons and the under surface of the acromion. With repetitive use (eg. tennis, swimming, lifting overhead) the tendons and bursa can become irritated and “impinge” on the acromion causing pain and dysfunction.

Who gets it?

Subacromial impingement is commonly seen in individuals that participate in repetitive overhead movements, for example, volleyballers, swimmers, cricketers, electricians, carpenters, painters and hairdressers. Risk factors include advancing age, a history of heavy lifting, previous shoulder trauma (eg. dislocation or fracture), infection, and smoking history.

• Primary Impingement is more common in low load high repetition exposures, for example hairdressers and electricians. Irritation of structures passing under the acromion become irritated and inflamed, reducing the space between the head of the humerus and the acromion and causing impingement.

• Secondary Impingement is more common in high load overhead activities such as throwing and racquet sports, swimming and volleyball. Repeated stress at the end of range of movement causes primary shoulder instability. The increased laxity of the joint then results in impingement.

Diagnosing subacromial impingement

Subacromial impingement can be clinically diagnosed by a physiotherapist. A thorough interview will often identify key factors in the past and current history that predispose and contribute to this condition. Patient reported symptoms include pain (for example when raising the arm overhead or lying on the affected side at night), and difficulty with daily tasks such as dressing and hanging washing. Pain is often reported on the outer aspect of the shoulder, though it can refer into the upper arm and shoulder blade.

Signs of subacromial impingement include loss of range of motion of the shoulder joint in particular reaching up and behind the back, weakness of the muscles surrounding the shoulder, and shoulder blade (scapula) dysfunction.

What else could it be?

There are a variety of conditions that present with similar symptoms and signs to subacromial impingement. These include rotator cuff tendonitis, rotator cuff tears, osteoarthritis, frozen shoulder, and labral injuries. Subtle differences in the behaviour of these conditions help us to determine the primary cause of your symptoms and treat it effectively.

Do I need a scan?

A physiotherapist can usually diagnose subacromial impingement without the use of imaging. An in depth subjective and objective assessment which includes a cluster of tests can normally rule in or rule out subacromial impingement. In some instances, xray and/or ultrasound may be recommended to differentially diagnose symptoms and direct a course of treatment.

Treatment

Subacromial impingement is the culmination of a breakdown in shoulder biomechanics resulting in increased load and dysfunction.  

The causes of this are complex and multifactorial. For example, shoulder impingement in a swimmer might be due to reduced hip extension, resulting in increased drag in the water and increased load on the shoulder internal rotators to achieve propulsion. In a fast bowler (cricket), it might be caused by altered thoracic (and consequently shoulder) alignment during ball release. Treatment and rehabilitation must be goal-oriented and designed for the individual, and closely monitored and progressed by a physiotherapist.

Research shows that early treatment should focus on reducing pain and inflammation and early therapeutic exercise. Physiotherapist’s can advise about relative rest, avoiding aggravating activities, application of heat or ice, and gentle range of motion activities. Manual and soft tissue therapy may assist with reducing pain and improving shoulder function.

The early phase of rehab is the perfect time to start to address weaknesses and restrictions in other areas that are contributing to symptoms. This might include hip stretches, trunk mobility, or core strengthening exercises, with cross training used to maintain general fitness.

Scapula strengthening is critical and forms the foundation for a successful recovery.

Most cases of subacromial impingement will improve significantly if scapula dysfunction is correctly identified and a therapeutic exercise program prescribed and adhered to. This should be implemented as soon as pain permits and gradually progressed to incorporate rotator cuff and functional shoulder retraining exercises, including appropriate strength, power, endurance, and proprioceptive activities. 

Should I get a steroid injection? Or surgery?

In recalcitrant cases corticosteroid injections have been shown to provide short term pain relief and improve function when combined with physiotherapy and exercise. If conservative management and the use of corticosteroid injections have not been effective surgery can be considered.

Research comparing conservative management (including physiotherapy)

and surgical management showed similar outcomes for shoulder function

at both 3, 6 and 12 months after interventions.

How long’s it going to take?

Subacromial impingement is the result of a prolonged period of movement dysfunction and loading. It will take some time to reverse these changes and improve movement patterns. On average we find it takes 3-6 months to reduce pain and improve scapula function. Full resolution of shoulder symptoms and contributing factors can be achieved over a longer period (6-12 months), and future shoulder injury risk minimised with an ongoing exercise routine. 

The Take Home

Subacromial impingement is a painful condition that impacts normal shoulder function. Symptoms usually develop over time and are closely related to poor posture, scapula dysfunction and repetitive loading. Subacromial impingement responds well to conservative management, particularly therapeutic exercise. By working closely with a physiotherapist, individuals suffering from subacromial impingement can achieve optimal outcomes and reduce their risk of a recurrence.

Got shoulder pain and want to get it sorted? Give us a call now.

At Movement for Life Physiotherapy, we can assess and diagnose the cause of your shoulder pain and let you know whether you have subacromial impingement, injured your labrum, torn your rotator cuff muscles, or if there is something else going on. With a clear diagnosis and tailored management plan, we'll help get you back to the things you love sooner.

Call us now on 08 8945 3799 or click on BOOK AN APPOINTMENT to book online.

Sources

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