Reaching into a high cupboard, fastening a seatbelt or putting on a coat should not produce a sharp pinch at the top or outer side of the shoulder. Yet these are common moments when shoulder pain becomes impossible to ignore. Understanding what causes shoulder impingement syndrome can help explain why the pain has developed and why the right treatment depends on an accurate diagnosis rather than a one-size-fits-all exercise programme.
Shoulder impingement syndrome is a term often used when the rotator cuff tendons or the bursa – a small fluid-filled cushion that reduces friction – become painful as the arm is raised. The pain can be local, travel down the upper arm, disturb sleep or make overhead activity feel weak and unreliable. Although the word ‘impingement’ suggests that something is simply being trapped, the reality is usually more complex.
What causes shoulder impingement syndrome?
The shoulder is designed for mobility. The ball at the top of the upper arm sits in a relatively shallow socket, and the rotator cuff muscles and tendons work continuously to keep it centred while the arm moves. This freedom of movement is useful, but it means the shoulder relies heavily on good tendon health, muscle control and coordinated movement from the shoulder blade.
Symptoms commonly arise when the rotator cuff or bursa is irritated during repeated lifting or reaching. In some people, there is reduced space beneath the acromion, the bony part of the shoulder blade that forms the roof over the tendons. A curved or prominent acromion, bony change linked to arthritis in the acromioclavicular joint, or a thickened bursa may contribute to pressure in this area.
However, anatomy alone rarely tells the whole story. Many people have bony changes on a scan without pain, while others have significant symptoms with little obvious narrowing. Tendons can become sensitive because of overload, age-related wear, a sudden injury, weakness around the shoulder, stiffness, or altered shoulder-blade movement. For this reason, a specialist assessment looks at how the shoulder functions as well as what an X-ray, ultrasound or MRI scan shows.
Tendon overload and rotator cuff problems
The rotator cuff includes four muscles whose tendons stabilise and move the shoulder. The supraspinatus tendon is particularly often involved in painful overhead movement. Repeated activity can overload this tendon, especially when workload rises faster than the tendon can adapt.
This may happen after returning to the gym, decorating for several weekends, starting a manual role, or increasing swimming, tennis or racquet sports. It can also occur without a dramatic change in activity. A tendon that has gradually become less resilient with age may become painful after an otherwise ordinary reach or lift.
Tendinopathy describes changes within a tendon that can make it painful and less able to tolerate load. It does not automatically mean there is a tear, and pain severity does not always match the appearance of the tendon on a scan. Some partial or full-thickness rotator cuff tears are more likely after a fall, a forceful pull or an injury, particularly in adults over 50. These need careful assessment because treatment decisions depend on the size and pattern of the tear, strength, function and the person’s goals.
Inflammation of the bursa
The subacromial bursa sits between the rotator cuff and the top of the shoulder. When it becomes inflamed or thickened, raising the arm can be particularly painful. This is known as bursitis and may occur alongside tendon irritation.
Bursitis can make lying on the affected side uncomfortable and can cause a painful arc – discomfort that is most noticeable as the arm moves through a middle range, rather than only at the beginning or end of movement. It may settle with activity modification and rehabilitation, but persistent symptoms should not be dismissed as simple inflammation. The underlying cause still needs to be understood.
Stiffness and movement control can add to the problem
A shoulder does not work in isolation. The shoulder blade, upper back, neck and rotator cuff all contribute to efficient lifting. If the shoulder blade does not rotate or stabilise well, the rotator cuff may have to work harder. Weakness, fatigue, poor movement control or long periods spent in a rounded sitting posture can therefore aggravate an already sensitive shoulder.
Stiffness may also play a part. Tightness at the back of the shoulder can alter the path of movement, while osteoarthritis or previous injury can reduce normal joint motion. In some adults, early frozen shoulder is mistaken for impingement because both conditions can cause pain when reaching. Frozen shoulder usually progresses to marked stiffness in several directions, particularly external rotation, and requires a different management plan.
This is why generic advice to ‘strengthen the shoulder’ can be unhelpful if it is not matched to the actual problem. The right exercises for a painful but mobile rotator cuff are not necessarily the right approach for a shoulder with a tear, arthritis, instability or developing frozen shoulder.
Age, injury and health factors
Shoulder impingement-type symptoms become more common in middle age because tendons change over time and may be less tolerant of sudden heavy loads. This is not an inevitable consequence of getting older, nor does it mean that surgery is required. It does mean that persistent pain, loss of strength or disturbed sleep deserves a proper diagnosis.
A previous shoulder dislocation, collarbone injury or fracture can change mechanics around the joint. Diabetes and thyroid disease are more strongly associated with frozen shoulder, which may coexist with rotator cuff pain. Smoking can affect tendon health and healing. Work that involves repetitive overhead tasks, such as painting, electrical work, warehouse duties or hairdressing, can keep the symptoms active if the shoulder is not given the opportunity to recover.
There is also an important difference between pain that develops gradually and pain that begins immediately after trauma. A sudden injury followed by inability to lift the arm, a clear loss of power, deformity, severe bruising or altered sensation should be assessed promptly.
Why an accurate diagnosis matters
‘Shoulder impingement’ is often used as a convenient label, but similar symptoms can come from several conditions. Rotator cuff tendinopathy, bursitis, a rotator cuff tear, acromioclavicular joint arthritis, glenohumeral arthritis, frozen shoulder and pain referred from the neck can all cause difficulty with lifting the arm.
A clinical examination helps identify the pattern of pain, range of movement, strength and signs of instability or neck involvement. Imaging is used when it will answer a relevant question. X-rays can show arthritis, bony shape and calcification. Musculoskeletal ultrasound can assess the rotator cuff and bursa dynamically as the shoulder moves. MRI may be useful when a tear, deeper joint problem or surgical planning is being considered.
At Droitwich Knee Clinic, a consultant-led one-stop assessment can combine examination and appropriate imaging with a clear, personalised plan on the same day where suitable. This can be particularly valuable when symptoms have persisted despite treatment, there has been an injury, or patients need clarity before deciding how to manage work, sport or daily activities.
Treatment follows the cause, not just the label
For many people, initial treatment focuses on reducing aggravating load without stopping all movement. Completely resting the shoulder for a prolonged period can lead to stiffness and weakness. Instead, a tailored rehabilitation programme usually aims to restore comfortable movement, improve rotator cuff and shoulder-blade control, and gradually build tolerance for the activities that matter to the patient.
Simple pain relief may help some people remain active enough to rehabilitate, provided it is safe for their individual health circumstances. A steroid injection into the subacromial bursa can reduce pain in selected cases, particularly when bursitis is preventing progress with physiotherapy. It is not a cure for a torn or overloaded tendon, and repeated injections need careful consideration because they may affect tendon quality. The potential benefit, timing and alternatives should be discussed in the context of the scan findings and examination.
Surgery is not the first answer for most impingement-type shoulder pain. It may be considered for a significant rotator cuff tear, persistent symptoms with a clearly defined structural cause, or when a well-delivered non-operative programme has not restored acceptable function. Rotator cuff repair is designed to repair an appropriate tear, but recovery requires commitment to rehabilitation and takes time. The decision should balance pain, strength, work demands, activity goals and the likelihood of improvement without an operation.
When to seek specialist advice
Arrange assessment if shoulder pain lasts beyond a few weeks, regularly wakes you at night, limits work or hobbies, or is associated with noticeable weakness. Seek more urgent advice after an injury if you cannot raise the arm, the shoulder looks out of shape, or you have numbness, worsening weakness, fever or feel unwell.
A painful shoulder is not always caused by something being pinched. Often, it is the result of a tendon or bursa that has become less able to cope with the demands placed on it, sometimes alongside stiffness or structural change. Clear diagnosis creates a more confident route forward – whether that means targeted rehabilitation, an injection to settle pain, further imaging or a discussion about repair.