Shoulder Impingement Syndrome

Shoulder Impingement

Impingement syndrome is sometimes called swimmer’s shoulder or thrower’s shoulder and is caused by the tendons of the rotator cuff becoming trapped as they pass through the shoulder joint. It may follow a partial tear of a rotator cuff tendon, or come on gradually through overuse. Resting the shoulder and treating it as soon as possible will help to prevent long term damage.

On this page:

  • Symptoms & diagnosis
  • Causes & anatomy
  • Treatment & rehabilitation

Impingement syndrome symptoms & diagnosis

Symptoms of impingement syndrome in the shoulder include pain which comes on gradually over a period of time. There will be a pain at the front and outside of the shoulder joint, especially during overhead movements such as in throwing, racket sports, and swimming.

There may be a pain in the shoulder when the arm is held out to the side turned outwards (abduction and external rotation). A particular give away sign of impingement is a pain in a 60-degree arc from about 70 degrees to 130 degrees when lifting the arm out sideways and up above the shoulder.

A professional therapist will perform a number of assessment tests to diagnose the cause of pain and shoulder impingement including:

  • Observation - The therapist will examine the shoulder, looking for swelling, bruising, muscle wasting, postural issues etc. It is important that the injured side is compared to the unaffected side at all times.
  • Palpation - The therapist will feel all around the shoulder, asking if there are any painful points and also feeling for muscular tightness and changes in skin temperature/texture.
  • Range of motion - The therapist will test the range of motion at the shoulder, both actively (the patient moves) and passively (the therapist moves the arm and the patient relaxes). This should always be compared to the uninjured side for what is normal for each individual, but also compared to 'normal' guidelines.
  • Resisted muscle tests - The therapist will ask you to move your shoulder against resistance (usually provided by them pushing against you). Weakness compared to the uninjured side or pain during shoulder rotation or abduction indicates injury to the rotator cuff, which may be due to impingement.

Specific shoulder impingement tests

  • Empty Can Test - You will be asked to put your arm out in front of you at a 45-degree angle to your body, with the thumb pointing to the floor (as if holding an empty can). The therapist will ask you to raise your arm whilst they resist your movement. This tests the Supraspinatus tendon.
  • Neer’s Sign - The therapist will position your arm with the thumb facing down and at a 45-degree angle to your body. They will then lift your arm up, above your head. If you experience pain or discomfort, you may have an impingement of supraspinatus.
  • Hawkins-Kennedy Test - Your arm will be raised in front of you to 90° and the elbow bent. The therapist will then medially rotate (turn the wrist down and elbow up) the arm. If this causes pain you probably have an impingement of Supraspinatus.

An X-Ray or MRI may be used to identify what is causing the impingement.

Shoulder impingement causes & anatomy

What is impingement syndrome? Impingement of the shoulder, which is sometimes called swimmer’s shoulder or thrower’s shoulder, is caused by the tendons of the rotator cuff muscles becoming trapped or impinged as they pass through a narrow bony channel called the subacromial space. The subacromial space is so called because it is under the arch of the acromion. With repetitive pinching, the tendons become irritated and inflamed.

This can lead to thickening of the tendon which may cause further problems because there is very little free space, so as the tendons become larger, they are impinged further by the structures of the shoulder joint and the muscles themselves.

There are at least nine different diagnoses which can cause impingement syndrome which includes bone spurs, rotator cuff injury, labral injury, shoulder instability, biceps tendinopathy, and scapula dysfunction. If left untreated, shoulder impingement can develop into a rotator cuff tear. The supraspinatus muscle is probably the most commonly involved in impingement syndrome of the shoulder.

Impingement Syndrome in itself is not a diagnosis, it is a clinical sign. There are at least nine different diagnoses which can cause impingement syndrome which includes bone spurs, rotator cuff injury, labral injury, shoulder instability, biceps tendinopathy, and scapula dysfunction. If left untreated, shoulder impingement can develop into a rotator cuff tear.

It is thought shoulder impingement begins as an overuse injury of the supraspinatus tendon which runs along the top of the shoulder blade. Pain then prevents the rotator cuff muscles from working properly which causes the upper arm bone to shift slightly. This may also result in inflammation of the bursa or small sack of fluid (subacromial bursitis).

Over time the pain causes more dysfunction and impingement in a vicious circle which may eventually lead to ossification or bony spurs growing and causing injury to the rotator cuff tendons and so on. So it is vitally important that impingement syndrome is rested and treated as soon as possible to avoid long-term damage.

Shoulder impingement is classified as internal or external depending on the causes:

External impingement

External shoulder impingement is classified as primary or secondary.

  • Primary external impingement is usually due to bony abnormalities in the shape of the acromial arch in the shoulder joint. It can sometimes be due to congenital abnormalities are known as os acromial, or due to degenerative changes, where small spurs of bone grow out from the arch with age, and impinge on the tendons.
  • Secondary external impingement is usually due to poor scapular or shoulder blade stabilization which alters the physical position of the acromion, hence causing impingement on the tendons. Is often due to a weak serratus anterior muscle and a tight pectoralis minor muscles. Other causes can include weakening of the rotator cuff tendons due to overuse for example in throwing and swimming, or muscular imbalance with the deltoid muscle and rotator cuff muscles.

Internal impingement

This occurs predominantly in athletes where throwing is the main part of the sport, e.g. pitches in baseball or javelin throwers. The underside of the rotator cuff tendons impinges against the glenoid labrum. This tends to cause pain at the back of the shoulder joint as well as sometimes at the front.

Treatment & rehabilitation

The aim of a shoulder impingement syndrome rehab program is to reduce pain and inflammation, improve or maintain mobility of the shoulder, strengthen any weak muscles and correct postural problems before returning to full fitness.

What can the athlete do?

Rest from all aggravating activities, especially those involving overhead movements. Every time you catch the tendons in the joint causing pain you may be making the condition worse. Maintain aerobic fitness on a stationary cycle. This period of rest, icing and anti-inflammatory medication should last up to a week.

Apply the PRICE principles of protection, rest, ice, compression, and elevation. Rest the shoulder from any painful activities or movements. Pain indicates increasing inflammation and delaying the healing process. Apply ice or a cold therapy and compression wrap to the painful area for 10-15 minutes per hour initially reducing to 3 or 4 times a day as symptoms reduce. Remember to use an ice bag or a towel wrapped around the ice to protect against ice burn.

What can a sports injury professional do?

NSAID's (Non-Steroidal Anti-Inflammatory Drugs) e.g. Ibuprofen may be prescribed by a doctor. Athletes with asthma should not take Ibuprofen. The drugs may help in the early stages of rehabilitation (first few days) but longer term is unlikely to help as much. They may also use electrotherapy such as ultrasound to reduce pain and inflammation. Sports massage can be used to help relax any tight muscles, such as the rotator cuff and upper back muscles.

They may discuss the option of directly injected steroids into the subacromial space to reduce inflammation and reduce inflammation in the local area although this is not usually an early option. It is usually recommended after a period of at least 6-12 months.

Exercises

Mobility & stretching

Full mobility of the shoulder joint is key in the rehabilitation of this injury. If there is insufficient mobility in the joint then the condition is likely to reoccur as the shoulder will not function correctly and allow enough space for the tendons to exist.

Mobility exercises should begin as soon as pain will allow and should avoid any areas of movement that do cause pain. Generally, any movements that involve lifting the arm out to the side (abduction) above horizontal should be done with the arm rotated outwards. The same applies to movements lifting the arm up forwards (flexion).

Stretching is also very important. Stretches should be held for 30 seconds at a time. These exercises can begin after 2-3 days, provided they are pain-free and should continue throughout the rehabilitation programme and beyond.

Strengthening

Strengthening the rotator cuff muscles is the key to strengthening the shoulder. It is important to get an equal balance of strength between the external and internal rotators at the shoulder. It is thought that an imbalance of strength here will contribute to the likelihood of impingement.

Strengthening exercises can begin after a week or so's rest and mobility exercises, provided they are pain-free. Start with gentle rotator cuff strengthening exercises, with the arm by your side and progress gradually.

Read more on shoulder impingement exercises.

Correcting postural issues

Shoulder impingements are common in individuals with poor posture and scapula (shoulder blade) movement dysfunctions. This is commonly caused by tightnesses in the chest muscles (especially pectoralis minor), which pull the shoulder blade forward.

Also, weakness in the upper back muscles, particularly serratus anterior, which allows the shoulder blade to be pulled forward by the chest muscles. Working on improving the posture can begin from day one, through demonstrations of good posture and chest stretching. This can be progressed to include scapula setting and stabilisation exercises.

This article has been written with reference to the bibliography.