Shoulder Impingement vs Rotator Cuff Tear: How to Tell the Difference in BC

Both conditions hurt in roughly the same place. Both make it hard to reach overhead or behind the back. Both tend to disturb sleep. This is why shoulder impingement and a rotator cuff tear get confused so often, and why many people either manage the wrong thing for months or worry unnecessarily about needing surgery. The distinction is real, it changes the treatment, and a physiotherapy assessment can usually sort them apart without imaging.

What shoulder impingement is

Subacromial impingement describes a mechanical problem: the supraspinatus tendon (one of the four rotator cuff tendons) is being compressed between the top of the upper arm bone and the bony shelf above it (the acromion) during shoulder movement. The tissue is irritated and sometimes inflamed, but there is no structural damage to the tendon itself.

Pain sits at the outside of the upper arm or the front of the shoulder. The most telling pattern is a painful arc between roughly 60 and 120 degrees of arm elevation, with less pain below that range and sometimes less pain again at the top. The shoulder is painful with movement but typically has preserved strength. You can usually lift the arm away from your body if someone asks you to, even if it hurts to do so.

What a rotator cuff tear is

A rotator cuff tear is actual fiber disruption in one or more of the tendons. Most commonly this is the supraspinatus. Tears are described as partial-thickness (the tendon is frayed or partly through) or full-thickness (the tendon is torn all the way across). They arise in two main ways: gradually over years through wear and repeated small stresses, or suddenly after a fall onto the arm or a hard yank on the shoulder.

The distinction between a degenerative tear (gradual) and a traumatic tear (sudden) matters for timing. A traumatic full-thickness tear in a younger or active person may need prompt assessment and surgical discussion, because delay can make a repair technically harder. A degenerative tear that has built up over time is typically approached with a trial of physiotherapy first, the same approach described in the rotator cuff injury guide.

How the symptoms differ in practice

This is where educational framing has limits. The patterns below are common and clinically useful, but they are not a diagnostic checklist you can use on yourself. They explain what a physiotherapist is looking for and why.

Impingement presentation: painful arc at mid-range of arm elevation, pain reaching overhead or across the body, pain with repetitive reaching. Strength is largely preserved. Lying on the affected shoulder is uncomfortable but not dramatically so.

Rotator cuff tear presentation: more constant pain, often noticeably worse at night. The distinguishing feature is weakness. Difficulty actively lifting the arm away from the body, or significant loss of strength compared to the other side, shifts the picture toward a tear. A full-thickness tear sometimes produces a catching or clunking sensation, or makes it nearly impossible to hold the arm up at certain angles.

The overlap is real. A large partial tear can produce similar weakness to a small full-thickness tear. A very irritable impingement can mimic tear-level pain. And both can be present at the same time: a shoulder with longstanding impingement can develop a partial tear in the same tendon. This is precisely why the pattern of symptoms is a starting point for assessment, not a conclusion.

The relationship between the two conditions

Impingement is often part of the pathway that leads to a degenerative tear. Repeated compression of the supraspinatus tendon, over months or years, generates friction and wear at the point where the tendon passes under the acromion. Over time that wear can progress from tendinopathy (tendon irritation without structural damage) to a partial tear, and in some cases to a full-thickness tear.

This is one reason early management of shoulder impingement matters. Addressing the rotator cuff weakness and scapular control problems that allow the humeral head to ride too high is not just about resolving current pain. It is about reducing the mechanical load that drives that long-term wear. The exercises used in shoulder impingement physiotherapy are aimed at that exact problem.

What a physiotherapy assessment actually tests

A physiotherapist examining a shoulder uses specific orthopaedic tests to narrow the picture. The tests do not give a definitive tissue diagnosis on their own, but used together with strength testing and movement assessment they tell a much clearer story than symptom location alone.

Impingement tests: Neer's test and Hawkins-Kennedy are the most commonly used. Both reproduce impingement symptoms by compressing the supraspinatus under the acromion through specific arm positions. A positive response does not confirm an impingement is the sole problem, but it supports it.

Rotator cuff integrity tests: the empty can test places the arm in a position that loads the supraspinatus in isolation, then applies downward resistance. Significant weakness or pain compared to the other side is a flag. The drop arm test asks whether the person can hold the arm elevated against gravity. Inability to do so (the arm "drops") is a sign of significant tendon disruption.

Strength testing across multiple planes: assessing strength in internal rotation, external rotation, abduction, and flexion gives a more complete picture of which part of the cuff is involved and how much function remains.

Movement and scapular assessment: how the shoulder blade moves during arm elevation matters. A scapula that tips or wings at certain angles changes how the subacromial space opens and closes, and influences how both impingement and a tear behave.

When imaging matters

For most presentations of shoulder pain that have been building gradually, imaging does not change what happens in the first few weeks of treatment. A physiotherapist can start a loading program based on the assessment findings, and the program in early stages is similar whether the diagnosis is impingement, tendinopathy, or a partial tear.

Imaging becomes relevant in specific situations. If strength is significantly reduced and does not improve after several weeks of well-designed physiotherapy, ultrasound or MRI can confirm tear size. That information guides whether surgery needs to be part of the conversation. For acute presentations where the shoulder failed suddenly after trauma and the person cannot lift the arm, imaging is appropriate sooner. And if a physiotherapist suspects a larger structural problem from the assessment, the referral for imaging happens promptly.

The point is that "should I get an MRI first" is usually not the right starting question. The right starting question is "should I get an assessment."

How treatment differs between the two

The approach to impingement and to a rotator cuff tear overlap more than they diverge, especially in the early stages.

For impingement, the program focuses on restoring rotator cuff strength and scapular control so the humeral head is better centred during arm movement. Load is progressed as tolerated. Return to overhead activity is the goal.

For a partial tear, the approach is similar but generally more conservative in early loading. The tendon has structural disruption, so load is introduced more carefully and the ramp-up period is longer. Timeline expectations are set accordingly.

For a full-thickness tear, physiotherapy is still often trialed first, particularly for degenerative tears in people whose functional demands can be met through strengthening rather than surgical repair. For larger tears, or tears with significant weakness that does not respond to rehab, surgery is brought into the discussion. A surgeon and imaging make that call, not a website. The physiotherapist's role is to coordinate the referral and keep the rehab moving in the meantime.

For cases where conservative care has stalled, shockwave therapy is sometimes discussed alongside or as a bridge to continued physiotherapy, particularly for calcific presentations.

What to do if your shoulder hurts now

If your shoulder has been sore for more than two to three weeks, the assessment is the productive next move. You do not need a diagnosis before booking. Physiotherapists in BC, regulated by the College of Health and Care Professionals of BC, are trained to screen and assess shoulder problems, sort the patterns that need imaging from those that can be managed directly, and refer to a physician or specialist when that is the appropriate step.

A shoulder that has been hurting for months and has been managed with generic shoulder exercises is often not being treated for the right problem. The assessment identifies which tissues are involved, what the load tolerance is, and what a realistic recovery timeline looks like. Starting there is more efficient than experimenting with exercises and waiting.

Frequently asked questions

Can a physiotherapist diagnose a rotator cuff tear without imaging?

A physiotherapist cannot give a tissue-level diagnosis (that requires imaging), but the assessment can identify the pattern of weakness, pain behaviour, and test results that strongly suggest a tear and warrant imaging. For most presentations, that distinction does not change the initial treatment approach.

Is it safe to do shoulder exercises if I might have a tear?

For mild to moderate weakness with a gradual onset, it is generally safe to begin a physiotherapy program. The program is designed around your current level of function and tissue tolerance. If the clinical picture suggests a significant tear, particularly after trauma, a physiotherapist will advise on appropriate activity and refer for imaging if indicated.

How do I know if my shoulder pain is serious?

Sudden inability to lift the arm after a fall or injury, significant weakness that develops quickly, numbness or tingling running down the arm, or a hot and swollen joint with fever are all reasons to seek prompt medical attention rather than a self-managed exercise plan. Persistent pain for more than two to three weeks without improvement warrants an assessment.

Does a rotator cuff tear always need surgery?

No. Many rotator cuff tears, particularly smaller and degenerative ones, are managed effectively with physiotherapy. The evidence supports conservative management as the starting point for most tears. The cases where surgery is more likely to be recommended earlier are traumatic full-thickness tears in younger or active people, or large tears with significant weakness that does not respond to a genuine trial of rehab.

What is the difference between a physio assessment and an MRI for shoulder pain?

An MRI shows the structural state of the tissue: tear size, location, and degree of damage. A physio assessment shows how the shoulder is functioning: what movement patterns are altered, where strength is reduced, and how the clinical tests respond. Both give useful information, but for most non-traumatic shoulder presentations, the assessment comes first because it changes the treatment plan immediately. Imaging confirms structural details when that information affects a surgical decision.

This article is general information, not personal medical advice. A regulated physiotherapist can assess whether the patterns described apply to your situation.

Sources

• Diagnosing, Managing, and Supporting Return to Work of Adults With Rotator Cuff Disorders: A Clinical Practice Guideline (JOSPT, 2022)
• The Efficacy of Exercise Therapy for Rotator Cuff–Related Shoulder Pain According to the FITT Principle: A Systematic Review With Meta-analyses (JOSPT, 2024)
• Conservative versus surgical management for patients with rotator cuff tears: a systematic review and meta-analysis (BMC Musculoskeletal Disorders, 2021)
• College of Health and Care Professionals of BC — Physical Therapists