On a shoulder scan report there are two terms that sound like the same thing and are not: glenohumeral osteoarthritis and acromioclavicular osteoarthritis. They often appear together, on the same line. And the difference between the two completely changes how much it is worth worrying.
The first is also called omarthrosis. The second is, in most cases, a finding that almost everyone has.
The two joints of the shoulder
The glenohumeral joint is the shoulder as you picture it: the head of the humerus moving inside the glenoid, the small cavity of the scapula. It is the most mobile joint in the body, and when it wears down the main symptom is not only pain: it is loss of movement, in particular of external rotation, the action of moving your hand outwards while keeping your elbow at your side.
The acromioclavicular joint is something else entirely: a small joint on top of the shoulder, where the end of the clavicle meets the acromion. You can find it with one finger, and it is painful at a very precise spot. The movement that flares it is bringing the arm across the front of the chest.
Acromioclavicular osteoarthritis: the finding almost everyone has
This is where the most useful numbers on this page are.
A systematic review gathered ten studies covering 1,831 shoulders of people who were not seeking treatment. It found changes consistent with acromioclavicular osteoarthritis in 48% of 953 skeletal findings and in 70% of 210 MRI scans of shoulders without symptoms.
A 2025 review of 31 studies goes even higher: in population data the prevalence ranges from 85% on MRI to 95% on X-ray. And the figure that matters most: among studies that included both shoulders with symptoms and shoulders without, the prevalence ranged from 13% to 95% in those without and from 20% to 100% in those with, meaning it often overlaps.
The conclusion of the authors of the first review deserves to be quoted in full, because it is a rare recommendation of caution: since a finding this common greatly lowers the probability that it is the cause of the symptoms in a single case, a diagnosis of symptomatic acromioclavicular osteoarthritis should be made sparingly, bearing in mind the potential harm of a diagnosis that can lead to an operation to remove the end of the clavicle.
In short: finding it written down is the norm. Attributing the pain to it requires that the pain is at that spot, flares with that movement, and that nothing else explains the story better.
Glenohumeral osteoarthritis: the one that takes away movement
Glenohumeral osteoarthritis is less common and behaves differently. The typical picture:
- deep pain, not localisable with one finger;
- stiffness that increases over time, especially in external rotation;
- difficulty getting dressed, reaching your hand behind your back, washing your hair;
- sometimes clicking or grinding during movement.
Progressive stiffness is the element that sets it apart from the more common shoulder pain linked to the rotator cuff, where passive movement usually remains. If your shoulder has stiffened quickly and hurts even at night, however, the first thing to rule out is something else: frozen shoulder.
What the research says about treatment
It needs to be said honestly, because the evidence is less solid than what you read about the knee and hip.
A review dedicated to the rehabilitation of glenohumeral osteoarthritis points out two things. First: few guidelines address this condition as a disease in its own right, and the available recommendations rely largely on low-quality evidence and expert opinion, with few high-level studies guiding decisions. Second: despite this, rehabilitation programmes have proved effective and reliable.
It is an uncomfortable but correct position: you do something reasonable, not something proven with the same degree of certainty as elsewhere.
What you work on, in practice
The movement you have. The realistic goal is not to restore the shoulder to how it was: it is to maintain and use the range you still have, because what is not used is lost quickly. Codman's pendulum exercise is often the starting point when moving hurts.
Rotator cuff strength. A shoulder with a worn joint leans even more on muscular control. The full progression is in shoulder strengthening exercises.
Load management. Not "do nothing overhead", but understanding which movements flare the shoulder, reducing them for a period and bringing them back gradually.
The practical rule on pain. A little discomfort during the exercise is acceptable; what matters is the next day. If the shoulder is worse, the load was too much.
The questions I am asked most often
"Heat or cold?" It is a preference, not a therapy. Neither changes the course of the condition: they make the part that does change it, namely movement, more bearable.
"Which exercises should I avoid?" There is no universal list. What reproduces your pain is temporarily reduced, and everything else is kept.
"Can I get a disability assessment?" This is a medico-legal evaluation that does not fall to a physiotherapist: it is requested from your GP or from a medico-legal doctor.
When you need a doctor
- Pain that appeared after a trauma, with inability to raise the arm.
- Fever, redness or heat over the shoulder.
- Worsening loss of strength, not just pain.
- Progressive night pain that does not change with position.
The other signs for which pain should be checked by a doctor are listed in when it is not physiotherapy.
In summary
These are two different types of osteoarthritis. The acromioclavicular one is found in almost everyone with age, up to 95% on X-ray in population data, and in similar percentages among shoulders with and without symptoms: finding it written down is not a diagnosis, and the authors recommend attributing pain to it sparingly. The glenohumeral one, omarthrosis, is less common and is recognised by the stiffness that advances.
For both, the work is the same, and it is less spectacular than one might hope: use the movement you have, strengthen the rotator cuff, dose the load. The evidence is weaker than for the knee and hip, and that should be said rather than hidden.
If you have a report in hand and do not know which of the two is your problem, the physiotherapists at Ri-Hub can look at it by video call: the session costs 29,90 € and the twenty-minute first consultation is free.
Sources
- Prevalence of acromioclavicular joint osteoarthritis in people not seeking care: A systematic review, Journal of Orthopaedics, 2022
- Imaging abnormalities of the acromioclavicular joint and subacromial space are common in asymptomatic shoulders: a systematic review, Journal of Orthopaedic Surgery and Research, 2025
- Glenohumeral osteoarthritis: overview, therapy, and rehabilitation, Disability and Rehabilitation, 2017
Last source check: September 2026.
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