Shoulder impingement syndrome is sometimes called swimmer’s shoulder, or thrower’s shoulder. It is caused by the tendons of the rotator cuff becoming trapped as they pass through the shoulder joint.
Impingement syndrome symptoms & diagnosis
Symptoms of impingement syndrome in the shoulder include:
- Pain with develops gradually over a period of days or weeks.
- Pain may be located to the front and outside of your shoulder joint.
- Symptoms are worse during overhead movements such as in throwing, racket sports, and swimming.
Shoulder assessment tests
A professional therapist will perform a number of assessment tests to diagnose the cause of your shoulder pain.
60 degree arc test
A common sign with shoulder impingement is a pain in a 60-degree arc when lifting your arm out sideways and up above the shoulder. Initially, you will feel little or no pain, then from about 70 degrees to 130 degrees pain is worse.
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.
What is shoulder 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. This channel is called the subacromial space and 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 even less free space. This is a viscous circle where the tendons become larger, they are impinged further by the structures of the shoulder joint and the muscles themselves.
What causes shoulder impingement?
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. These include:
- Bone spurs
- Rotator cuff injury
- Labral injury
- Shoulder instability
- Biceps tendinopathy
- Scapula dysfunction
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. If left untreated, shoulder impingement can develop into a rotator cuff tear. It is possible to have bony spurs growing but not have impingement symptoms.
Shoulder impingement is classified as internal or external depending on the causes:
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.
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.
Shoulder impingement syndrome treatment
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?
- Apply cold therapy 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 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.
- Maintain aerobic fitness on a stationary cycle. This period of rest, icing and anti-inflammatory medication should last up to a week.
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 for shoulder impingement
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 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.
References & further reading
- Seitz AL, McClure PW, Finucane S et al. Mechanisms of rotator cuff tendinopathy: intrinsic, extrinsic, or both? Clin Biomech (Bristol, Avon) 2011;26(1):1–12
- Wilk KE, Obma P, Simpson CD et al. Shoulder injuries in the overhead athlete. J Orthop Sports Phys Ther 2009;39(2):38–54.
- Balke M, Schmidt C, Dedy N et al. Correlation of acromial morphology with impingement syndrome and rotator cuff tears. Acta Orthop 2013;84(2):178–83.