What is Shoulder Impingement Syndrome?
Shoulder impingement syndrome is a condition where your shoulder’s bursa or rotator cuff tendons are intermittently trapped and compressed during shoulder elevation movements. Shoulder impingement can be very painful. Persisting shoulder impingement may cause shoulder bursitis or a structural injury to your rotator cuff tendons (rotator cuff tendinopathy or rotator cuff tear). Repeated impingement commonly results in painful shoulder movements in the first instance but can lead to considerable functional weakness with a full-thickness rotator cuff tear.
What is the Shoulder Impingement Zone?
Your shoulder impingement zone is where there is the least space available between your shoulder bones. The impingement occurs between the head of your humerus (shoulder’s ball-shaped bone) and the top of your shoulder blade (known as the acromion).
During normal shoulder function, there should not be an impact of the scapula’s bony acromion process into the soft bursa or rotator cuff tendons below. However, when your shoulder muscles are weak or in-coordinated, your movement pattern can become abnormal, and impingement may occur. The first sign of shoulder impingement is often a simple shoulder click, which progresses to a painful click, reduced movement and ultimately loss of shoulder function.
When impingement does happen, your bursa becomes repeated pinched and inflamed, and shoulder bursitis will develop. Likewise, repeated impingement into the rotator cuff tendon can and lead to rotator cuff tendinopathy. In severe cases, a rotator cuff tear. These conditions can co-exist or be present independently. The most common rotator cuff tendon impinged is your supraspinatus. You may occasionally hear that you have supraspinatus impingement or infraspinatus impingement. These definitions correlate to the specific tendon that is involved in the shoulder impingement.
Shoulder Impingement Symptoms
Shoulder impingement symptoms include:
- Pain or clicking when putting your hand behind your back or head.
- Pain reaching for the seat-belt or across your chest.
- An arc of shoulder pain approximately when your arm is at shoulder height or when your arm is overhead.
- Pain when lying on the sore shoulder.
- Shoulder pain at rest as your condition deteriorates.
- Muscle weakness or pain when attempting to reach or lift.
Shoulder Impingement Test
During your clinical examination, a skilled shoulder physiotherapist or doctor will diagnose your shoulder impingement. They will perform a series of shoulder impingement tests to rule in or out impingement. They will also assess for shoulder range of motion, rotator cuff strength, assess your scapular influence on the impingement plus other appropriate tests.
Real-Time Ultrasound Scan
Ultrasound scan is a relatively cheap and effective diagnostic test to visualise dynamic shoulder impingement and detect any associated injuries such as shoulder bursitis, rotator cuff tears, calcific tendonitis or shoulder tendinopathies. During your real-time ultrasound scan, the sonographer or radiologist can visualise what is happening as your shoulder moves through the impingement zone.
Does MRI Show Shoulder Impingement?
Shoulder impingement is unlikely to be viewed on MRI. MRI is a static test performed in a non-impingement zone, e.g. arm by your side. It may show rotator cuff tears or bursitis, but not whether there is dynamic impingement.
X-rays do not show impingement but can show whether bone spurs etc. have narrowed the subacromial space.
Please consult your health practitioner for the most appropriate clinical and diagnostic tests.
Who Suffers Shoulder Impingement Syndrome?
Impingement syndrome is more likely to occur in people who engage in physical activities that require repeated overhead arm movements, such as tennis, golf, swimming, weight lifting, or throwing a ball.
Occupations that require repeated overhead lifting or work at or above shoulder height are also at risk of rotator cuff impingement.
What Causes Shoulder Impingement?
While a traumatic injury, e.g. fall, can occur, it is repeated movement of your arm through the impingement zone that most frequently causes the bursa/rotator cuff to contact the outer end of the shoulder blade (acromion).
Postures that significantly narrow the subacromial space include:
- Your arm is directly overhead.
- Your arm is working at, through or near shoulder height.
- A rounded shoulder posture.
Your shoulders rotator cuff tendons protect themselves from simple knocks and bumps by bones (mainly the acromion) and ligaments that form a protective arch over the top of your shoulder. However, nothing is foolproof. Any of these structures can be injured, whether they be your bones, muscles, tendons, ligaments or bursas.
Injuries vary from shoulder bursitis to mild tendon inflammation (rotator cuff tendonitis), calcific tendinopathy (bone forming within the tendon) through to partial and full-thickness rotator cuff tendon tears, which may require surgery.
Gradual Onset Impingement
If the onset of your shoulder impingement was gradual, then your static and dynamic posture both require a thorough assessment. Your muscle strength, flexibility and spine shape all have essential roles to play and should be thoroughly assessed by your physiotherapist to plan and effectively guide your treatment. Gradual onset shoulder impingement regularly recurs due to your poor movement habits and the need to normalise those habits during your rehabilitation.
Rotator Cuff Involvement
Your rotator cuff is an essential group of control and stability muscles that maintain “centralisation” of your shoulder joint. In other words, it keeps the shoulder ball centred over the small socket. This central position prevents injuries such as impingement, subluxations and dislocations.
We also know that your rotator cuff provides stable, but subtle, glides and slides of the ball joint on the socket to allow full shoulder movement.
Once you suspect any rotator cuff injury, it is crucial to confirm the exact type of your rotator cuff injury since treatment does vary depending on the specific or combination of rotator cuff injuries.
Scapular (Shoulder Blade Involvement)
As the base of your whole upper limb’s stability, your shoulder blade (scapula) has a vital role as the central dynamic stable base (think crane base) that attaches your arm to your chest wall. Your arm then acts as a crane boom to perform a vast range of functional activities.
Poor scapular muscle control can tip the acromion into your shoulder bursa and rotator cuff, which may cause your dynamic shoulder impingement. In this instance, your rehabilitation should also include assessment and normalisation of your shoulder blade function.
Primary & Secondary Causes of Shoulder Impingement
Shoulder impingement has primary (structural) and secondary (posture & movement related) causes.
Primary Rotator Cuff Impingement – Structural Narrowing
Structural issues are what we are born with or a steady deterioration of our bone structure as we age. Because of this anatomical narrowing, you are more likely to squash, impinge and irritate the soft tissues in the sub-acromial space, which results in bursitis or shoulder tendonitis. Some of us are simply born with a smaller subacromial space. Conditions such as osteoarthritis can also cause the growth of sub-acromial bony spurs, which further narrows the subacromial space.
Secondary Rotator Cuff Impingement – Dynamic Instability
Impingement can occur if you have a dynamically unstable shoulder. If so, there is a combination of excessive joint movement, ligament laxity and muscular weakness around the shoulder joint. This impingement usually occurs over time due to repetitive overhead activity, trauma, previous injury, poor posture or inactivity.
In an unstable shoulder, the rotator cuff has to work harder, which can cause injury. An overworking rotator cuff fatigues and eventually becomes inflamed and weakens due to pain inhibition or tendon tears. When your rotator cuff fails to work regularly, it is unable to prevent the head of the humerus (upper arm) from riding up into the sub-acromial space, causing the bursa or tendons to become squashed.
Failure to properly treat this instability causes the injury to recur. Poor technique or bad training habits such as training too hard is also a common cause of overuse injuries, such as bursitis or tendinopathy.
Shoulder Impingement Treatment
Shoulder impingement may irritate numerous structures. Each structure may require a different treatment modality. The importance of understanding WHY the impingement has occurred in the first place is the most important step to both the short-term resolution and the prevention of recurrent shoulder impingements, which could predispose you to a rotator cuff tear and subsequent rotator cuff surgery.
Since your shoulder impingement injuries and treatment options can vary considerably, it is always important to arrange an appointment with your trusted healthcare practitioner who has a particular interest in shoulder injuries.
Researchers have concluded that there are mostly seven stages that need to be covered to rehabilitate shoulder impingement and prevent recurrence effectively.
- Early Injury: Protection, Pain Relief & Anti-inflammatory Treatment
- Regain Full Shoulder Range of Motion
- Restore Scapular Control and Scapulohumeral Rhythm
- Restore Normal Neck-Scapulo-Thoracic-Shoulder Function
- Restore Rotator Cuff Strength
- Restore High Speed, Power, Proprioception and Agility Exercises
- Return to Sport or Work
Shoulder Impingement Exercises
Due to the large variability between patients who experience shoulder impingement, each patient must receive a customised shoulder impingement exercise program. It makes sense that a swimmer who is suffering swimmers shoulder would receive a different exercise regime to a throwing athlete, or an elderly lady who is merely wishing to reach overhead to open a cupboard or hang their washing.
For more specific advice about your shoulder impingement, please contact your shoulder physiotherapist or doctor.