Understanding Subacromial Shoulder Pain: Causes, Symptoms, and Treatment Options
By Stephen Bunting, Specialist MSK Physiotherapist (UK)
If you’re experiencing a persistent, nagging pain in your shoulder or upper arm — especially when reaching overhead, lying on your side, or even just putting on a jacket — there’s a good chance you may be dealing with a common condition known as subacromial shoulder pain.
The information can also been seen in video format below.
What Is Subacromial Shoulder Pain?
The shoulder is one of the most mobile and complex joints in the body, made up of bones, muscles, tendons, and other soft tissue structures that all work together to provide the shoulder with its huge range of movement.
The subacromial space is the small area between the top of your upper arm bone (the humerus) and a bony arch above it called the acromion. Running through this space are the rotator cuff tendons, which help stabilise your shoulder, and a small fluid-filled sac called the bursa, which reduces friction.
When the rotator cuff becomes irritated or inflamed — often due to overuse or strain — pain typically develops around the outside of the upper arm (often referred to as the "sergeant’s stripe" area). This pain is usually triggered when reaching out, lifting overhead, or lying on the affected side at night.
You might hear this condition called:
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Subacromial pain syndrome (SAPS)
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Rotator cuff-related shoulder pain
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Or the older term, subacromial impingement
It’s one of the most common shoulder problems seen in physiotherapy clinics, especially among adults aged 40 to 65, although it can also affect older individuals.
What Causes Subacromial Shoulder Pain?
The causes are often multifactorial — meaning there’s rarely one single event that triggers it. Some common contributing factors include:
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Repetitive overhead activity (e.g., DIY, painting, or sports)
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Weakness or imbalance in the rotator cuff
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Poor posture or altered movement patterns
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Age-related tendon changes
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Sudden increases in physical activity
Most of the time, there’s no serious injury. The tendons are simply irritated or overloaded — and that’s good news, because it means the condition is usually very treatable with the right approach.
Primary vs. Secondary Subacromial Pain
Subacromial shoulder pain is often divided into two main types:
Primary Subacromial Pain:
This is usually caused by structural narrowing of the subacromial space. It can be due to:
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The natural shape of the acromion
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Thickened ligaments
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Osteoarthritic changes
These changes reduce the space available for the tendons and bursa, making them more likely to become compressed or “impinged” during movement.
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| Some causes of Primary Subacromial Pain |
Secondary Subacromial Pain:
This is far more common, and is due to functional instability — usually from weakness in the rotator cuff.
Think of the shoulder like a golf ball sitting on a tee. Unlike the hip, which has a deep socket to keep the joint stable, the shoulder’s socket is very shallow. The rotator cuff muscles help to keep the “ball” centred in the socket while larger muscles like the deltoid and pecs generate movement.
If the rotator cuff becomes weak, it can no longer maintain that fine control. The joint becomes slightly unstable, and the tendons begin to rub and irritate more easily — resulting in pain.
Regardless of whether your issue is structural or functional, the key point is this: most cases respond well to conservative treatment and don’t require surgery.
How Is It Diagnosed?
Subacromial shoulder pain is usually diagnosed clinically, based on your symptoms and a physical examination by a physiotherapist or doctor.
Scans are not always necessary, but they can provide additional insight in some cases:
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X-rays help assess the shape of the acromion and look for signs of arthritis.
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Ultrasound or MRI can detect issues with the rotator cuff tendons or bursa.
It’s important to note, however, that many people over 50 will have “abnormal” scan results — like small tendon tears or degenerative changes — even if they have no pain at all. So while imaging can be useful, it should always be interpreted in the context of your symptoms.
Conditions That Can Mimic Subacromial Pain
Not all shoulder pain is subacromial pain. Here are some other possibilities your clinician might consider:
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Frozen Shoulder: This tends to cause stiffness, particularly a loss of outward rotation. It usually develops more gradually and severely limits movement. (You can read more about frozen shoulder here).
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Shoulder Osteoarthritis: This usually shows up clearly on an X-ray and tends to cause deep joint pain and grinding.
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Neck-related pain (Cervical Radiculopathy): This can refer pain into the shoulder or arm and is often accompanied by numbness or tingling in the hand. The pain may feel strongest in the neck or radiate below the elbow.
How to Treat Subacromial Shoulder Pain
The good news? Most cases of subacromial shoulder pain will get better with the right approach. Here are the three main steps to recovery:
1. Reduce Aggravation
You don’t need complete rest — but you should avoid repeatedly aggravating movements, especially overhead lifting, heavy carrying, or sleeping directly on the painful side. Continuing to push through pain often makes things worse and slows your recovery.
Instead, modify how you move. A few simple changes to your daily routine can really help reduce strain on the shoulder.
2. Manage Sleep and Daily Life
Sleep is often affected. Try placing a pillow under your arm or hugging a cushion to reduce pressure when lying down. During the day, avoid keeping your arm still for long periods — gentle, pain-free movement promotes healing.
3. Start Rehabilitation
Rehabilitation is the most important part of your recovery. The goal is to restore rotator cuff strength and improve control of shoulder movement.
You can follow a step-by-step home rehab program designed specifically for subacromial shoulder pain in the video below. The exercises start gently and gradually build strength, helping to improve function and reduce pain over time.
When Should You Consider Other Treatments?
In some cases, additional treatments may be considered:
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Corticosteroid injections can reduce inflammation and pain in the short term, especially if symptoms are severe, sleep is disturbed or pain is preventing the ability to perform basic exercises.
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Shockwave therapy can sometimes be helpful but is best used alongside rehab, not instead of it.
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Surgery (such as subacromial decompression) is now considered a last resort — and evidence shows it’s rarely more effective than physiotherapy alone.
Final Thoughts
Subacromial shoulder pain is one of the most common and treatable causes of shoulder discomfort. With a clear understanding of what’s going on, and a structured approach to reducing irritation, improving movement, and restoring strength, most people make a full recovery — without the need for scans or surgery.
If you're struggling with shoulder pain and looking for expert, evidence-based guidance, explore the rehab resources and videos on this site to take the next step toward recovery.
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This article provides general information related to various medical conditions and their treatment. It is intended for informational purposes only and not a substitute for professional advice, diagnosis or treatment provided by a doctor or other qualified health care professional. The information provided does not constitute personal advice or guarantee of outcome and should not be used to diagnose yourself or others. You should never ignore advice provided by a health care professional because of something you have seen or read on this website. You should always consult a doctor or other qualified health care professional for personal medical advice.