Shoulder Impingement (Subacromial Shoulder Pain)

Shoulder impingement is a commonly used term for pain that occurs around the front or side of the shoulder, particularly when lifting the arm overhead. It is often associated with activities such as reaching, lifting, swimming, throwing or working with the arm above shoulder height.

Although the term “impingement” is still widely used, our understanding of this type of shoulder pain has changed. Traditionally, symptoms were thought to occur because structures such as the rotator cuff tendons or bursa were being mechanically “pinched” beneath the acromion as the arm was lifted.

We now understand that the picture is more complex. Shoulder pain in this region can involve the rotator cuff tendons, subacromial bursa and surrounding structures, while factors such as tendon capacity, activity levels, strength and recent changes in load may also contribute. For this reason, terms such as subacromial pain syndrome or rotator cuff-related shoulder pain are increasingly used.

In this guide, we’ll explain what shoulder impingement means, why the terminology has changed, common symptoms and causes, how it is assessed, and the treatment and rehabilitation options available.

What Is Shoulder Impingement?

Shoulder impingement is a term traditionally used to describe pain thought to occur when structures within the shoulder, particularly the rotator cuff tendons and subacromial bursa, become compressed beneath the acromion as the arm is lifted.

This explanation led to the idea that the shape or movement of the shoulder was mechanically “pinching” these tissues and causing pain. However, research has shown that the relationship between shoulder structure, compression and symptoms is not this straightforward.

The space beneath the acromion naturally changes as the arm moves, and structural findings seen on imaging do not always correspond with pain. Changes in the rotator cuff tendons or bursa can also be found in people who have no shoulder symptoms.

For this reason, clinicians increasingly use terms such as subacromial pain syndrome or rotator cuff-related shoulder pain. These terms recognise that symptoms may involve several structures and can be influenced by factors including tendon health, shoulder strength, activity levels and changes in the amount or type of load placed on the shoulder.

This does not mean that the term “shoulder impingement” is necessarily meaningless. It remains widely used and understood, particularly by patients. However, rather than thinking of something simply being “trapped” or “pinched”, it can be more helpful to view the condition as shoulder pain that develops when the tissues and surrounding muscles are having difficulty tolerating the demands being placed on them.

Why Has the Term “Shoulder Impingement” Changed?

For many years, shoulder impingement was explained primarily as a mechanical problem. The theory suggested that when the arm was raised, the rotator cuff tendons and subacromial bursa became compressed or “pinched” beneath the acromion, leading to irritation, inflammation and pain.

This explanation influenced treatment approaches, including exercises designed to alter shoulder mechanics and surgical procedures intended to create more space beneath the acromion.

However, our understanding has evolved. Research has shown that structural features of the shoulder do not consistently predict who will experience pain, and changes involving the rotator cuff tendons, bursa and surrounding structures are commonly seen on imaging in people without symptoms.

Importantly, studies comparing decompression surgery with non-surgical care have also questioned whether simply increasing the space beneath the acromion addresses the underlying cause of symptoms.

As a result, shoulder pain is now generally viewed as more complex than a single structure being mechanically pinched. Factors such as tendon capacity, muscle strength, activity levels, changes in workload, previous injury and individual characteristics can all influence how the shoulder responds to load.

The term subacromial pain syndrome is therefore often used to describe pain arising around this region without assuming that mechanical impingement is the sole cause. Rotator cuff-related shoulder pain is another commonly used term when the rotator cuff is thought to be an important contributor.

This change in terminology is useful because it shifts the focus away from the idea that the shoulder is structurally “damaged” or needs more space, and towards understanding how the shoulder is functioning and what can be done to progressively improve its capacity.

What Causes Subacromial Shoulder Pain?

Subacromial shoulder pain rarely has a single identifiable cause. Symptoms often develop when the demands placed on the shoulder exceed the current capacity of the rotator cuff and surrounding tissues to tolerate those loads.

This can happen following a sudden increase in activity, such as starting a new exercise program, increasing training volume, returning to sport after a break or performing more overhead work than usual. In other people, symptoms may develop gradually without an obvious change or injury.

Repetitive overhead activities can place greater demands on the shoulder. Swimming, tennis, throwing sports, weight training and occupations involving frequent reaching or working overhead may therefore contribute to symptoms, particularly when there has been a rapid increase in workload.

Age-related changes within the rotator cuff tendons can also influence how the shoulder responds to load. However, these changes are common and do not necessarily cause pain. Findings such as tendon changes or bursitis on ultrasound or MRI therefore need to be considered alongside a person’s symptoms and function.

Other factors such as shoulder strength, previous injury, recovery between activities and general health may also influence symptoms. In many cases, several factors are likely to contribute rather than one specific structure being responsible.

Understanding these factors is important because treatment does not necessarily require avoiding movement or trying to permanently “correct” the shoulder. Instead, management commonly focuses on modifying aggravating loads where necessary and progressively rebuilding the shoulder’s strength and capacity.

Symptoms of Subacromial Shoulder Pain

Symptoms of subacromial shoulder pain can vary between individuals, but pain is commonly felt around the front or outer aspect of the shoulder and upper arm. Symptoms are often associated with movements that place greater demand on the rotator cuff and surrounding tissues.

Pain may be noticeable when lifting the arm overhead, reaching away from the body or performing repeated shoulder movements. Activities such as putting something into a high cupboard, reaching into the back seat of a car, swimming, throwing or performing overhead exercises at the gym may become uncomfortable.

Some people experience a painful arc, where symptoms are more noticeable through part of the movement as the arm is raised and then reduce again towards the top of the movement. However, this finding is not specific to one particular shoulder structure and should be interpreted alongside other symptoms and examination findings.

Other symptoms may include:

Pain around the front or outside of the shoulder
Pain when lifting or reaching overhead
Discomfort when reaching behind the back
Pain with pushing, pulling or lifting activities
Reduced strength or confidence when using the arm
Pain when lying on the affected shoulder
Night pain that may disturb sleep
Difficulty with work, exercise or sporting activities

Symptoms do not always correspond directly with changes seen on imaging. Ultrasound or MRI findings involving the rotator cuff tendons or subacromial bursa need to be considered alongside the person’s pain, movement, strength and function.

How Is Subacromial Shoulder Pain Diagnosed?

Diagnosis usually begins with a discussion about how the shoulder symptoms developed, which movements or activities aggravate them, and how the problem is affecting everyday activities, work, exercise or sport.

A physical examination may assess shoulder movement, strength and function. The clinician may also use movements or resisted tests that reproduce the person’s symptoms and help determine whether the rotator cuff and surrounding structures are likely to be contributing.

Historically, several clinical tests were described as specific “impingement tests”. However, no single test can reliably diagnose subacromial shoulder pain or identify one particular structure as the source of pain. Assessment therefore considers the overall pattern of symptoms and examination findings rather than relying on one test alone.

Imaging is not always necessary. Many people can begin appropriate management based on their symptoms and clinical assessment without first having an ultrasound or MRI.

When imaging is indicated, ultrasound or MRI can provide information about the rotator cuff tendons, subacromial bursa and other shoulder structures. X-rays may sometimes be useful when other conditions affecting the bones or joints of the shoulder need to be considered.

Importantly, findings such as rotator cuff tendon changes or bursal abnormalities can also occur in people without shoulder pain. Imaging results therefore need to be interpreted alongside the person’s symptoms, strength, movement and function, rather than being considered a diagnosis on their own.

Treatment for Subacromial Shoulder Pain

Treatment for subacromial shoulder pain is usually non-surgical and focuses on reducing symptoms while gradually improving the shoulder’s ability to tolerate movement and load.

In the early stages, activities that significantly aggravate the shoulder may need to be temporarily modified. This could involve reducing heavy or repetitive overhead movements, adjusting gym exercises or changing the volume or intensity of sporting activity. Complete rest is generally not necessary, and continuing to use the shoulder within manageable limits can help maintain movement and strength.

Exercise and progressive rehabilitation are central to treatment. Rehabilitation may include exercises to improve shoulder movement, strengthen the rotator cuff and surrounding muscles, and gradually increase the shoulder’s capacity for the demands of everyday activities, work and sport.

Rather than attempting to permanently avoid movements thought to cause “impingement”, rehabilitation aims to progressively increase what the shoulder can comfortably tolerate. Exercises can therefore become more challenging as symptoms, strength and function improve.

Pain-relieving or anti-inflammatory medication may sometimes be considered in consultation with a GP or pharmacist. Corticosteroid injections may provide short-term pain relief for some people, although they do not address the shoulder’s underlying strength or capacity and are not generally considered a stand-alone long-term solution.

Surgery is not routinely required for subacromial shoulder pain. For most people, management should begin with education, appropriate activity modification and progressive exercise rehabilitation, with treatment tailored to the individual’s symptoms, goals and activity requirements.

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