Your shoulder is the most mobile joint in your body. It can swing through a greater range of motion than any other joint — reaching overhead, rotating behind your back, throwing, lifting. That range is exactly why it's so vulnerable. The more a joint moves, the more structures are in play, and the more ways things can go wrong.
The result is that "shoulder pain" is not one condition. It's a symptom that can come from at least eight distinct causes, each with a different mechanism, a different feel, and a different treatment path. Getting the right answer matters — because physiotherapy for a rotator cuff tear is very different from physiotherapy for a frozen shoulder, and treating the wrong thing delays recovery.
How the Shoulder Works — in Brief
The shoulder joint is a ball-and-socket: the rounded head of your upper arm bone (humerus) sits in a shallow socket on your shoulder blade (glenoid). This shallow socket is what gives the shoulder its range, but it also means the joint relies heavily on the surrounding soft tissue — the rotator cuff muscles and tendons, the labrum, the bursa, and the joint capsule — to stay stable and pain-free. When any of those structures are stressed, torn, inflamed, or deteriorated, pain follows.
There are also two other joints involved in shoulder movement: the acromioclavicular (AC) joint at the top of the shoulder, where the collarbone meets the shoulder blade, and the sternoclavicular joint where the collarbone meets the sternum. Problems in either can cause pain that feels like a shoulder problem.
1. Rotator Cuff Problems
The rotator cuff is a group of four muscles and their tendons that wrap around the shoulder joint. Together they hold the ball in the socket and power the arm's ability to rotate and lift. They're also the most commonly injured structure in the shoulder.
Rotator cuff problems sit on a spectrum. Tendinitis is inflammation of the tendons, often from repetitive overhead activity — swimming, throwing, racquet sports, or work that involves reaching above shoulder height repeatedly. It causes a dull, aching pain, typically on the outside of the upper arm, that worsens with use. Left unmanaged, tendinitis can progress to partial or full thickness tears, where the tendon fibres actually tear.
A rotator cuff tear can happen gradually, as years of wear thin the tendon until it gives, or suddenly from a single injury — a fall, a heavy lift, a forced movement. The pain from a tear is often sharp and may limit your ability to raise your arm or sleep on that side.
According to the American Academy of Orthopaedic Surgeons, rotator cuff injuries can result from direct trauma or from progressive wear and tear, and they're among the leading causes of shoulder pain in adults. They can often be treated without surgery, but some tears do require a procedure — and the right call depends on the size of the tear, your age, and how you're functioning.
2. Shoulder Impingement
Impingement is what happens when the soft tissues of the shoulder — specifically the rotator cuff tendons and the bursa above them — get pinched between the bones of the shoulder with certain movements.
The space between the head of the humerus and the acromion (the bony prominence at the top of your shoulder) is narrow. When the tendons or bursa in that space are inflamed or swollen, or when your shoulder mechanics aren't quite right, that space gets even tighter. Raising your arm in a particular arc produces a catching, painful sensation.
Impingement is closely linked to bursitis — inflammation of the bursa, a small fluid-filled sac that cushions the tendons. The two often occur together, and the treatment is broadly similar: reducing the inflammation, correcting the mechanics through physiotherapy, and addressing the underlying cause. Corticosteroid injections are sometimes used when conservative measures aren't making enough progress.
3. Frozen Shoulder (Adhesive Capsulitis)
Frozen shoulder is one of the most misunderstood shoulder conditions because it doesn't follow the usual rules: it often has no clear trigger, it follows a predictable three-stage course that can span one to three years, and it tends to improve on its own — though treatment can significantly shorten that timeline.
The joint capsule (the tissue sleeve surrounding the shoulder joint) thickens, tightens, and develops adhesions. Movement becomes progressively restricted. The condition moves through three stages:
- Freezing: Pain builds, range of motion starts to reduce. This stage typically lasts six weeks to nine months.
- Frozen: Pain may ease somewhat, but stiffness becomes the dominant problem. Daily tasks — reaching a shelf, putting on a jacket, fastening a seatbelt — become genuinely difficult.
- Thawing: Movement gradually returns, sometimes fully, over several months to a year or more.
Frozen shoulder is more common in people aged 40 to 60, and people with diabetes carry a significantly higher risk. A shoulder that's been immobilised after injury is also vulnerable, which is why early movement is encouraged after shoulder injuries where possible.
4. Shoulder Arthritis
Arthritis in the shoulder is less common than in the hip or knee, but it does occur, and it's worth understanding the different types.
**Osteoarthritis** develops when the cartilage covering the joint surfaces wears down over time. Bone rubs against bone, causing pain, stiffness, and a grinding or clicking sensation. It tends to develop gradually and worsen with activity.
**Rheumatoid arthritis** is an autoimmune condition in which the immune system attacks the joint lining (synovium), causing inflammation, swelling, and joint damage over time. Unlike osteoarthritis, it often affects both shoulders simultaneously and is accompanied by systemic symptoms.
**Post-traumatic arthritis** develops after a significant shoulder injury — a fracture, a dislocation — and can appear years after the original event. If you've had a serious shoulder injury in the past and are now developing stiffness and aching that worsens with activity, post-traumatic arthritis is worth investigating.
Treatment depends on how severe the arthritis is and how much it limits your function. Conservative options come first. Shoulder replacement is reserved for cases where the joint is significantly damaged and quality of life is substantially affected.
5. Shoulder Instability and Dislocation
A shoulder dislocation happens when the ball of the humerus is forced out of the socket — most commonly forward (anterior dislocation), which accounts for the large majority of cases. It's usually the result of a fall on an outstretched arm or a direct impact to the shoulder.
Dislocation is painful and immediately obvious: the shoulder loses its normal shape, arm movement is impossible, and the joint needs to be relocated. What matters beyond the immediate injury is what happens next. A first-time dislocation can stretch or tear the labrum (the cartilage rim that deepens the socket) and the surrounding ligaments, and young patients in particular face a high risk of recurrence.
Shoulder instability describes a shoulder that feels loose, unstable, or prone to giving way, even without a full dislocation. It can develop after a dislocation or gradually from repetitive overhead sport. The shoulder may slip partially out of the socket — a subluxation — and then relocate on its own. This is often described as the shoulder "popping" or "going out."
Some cases of instability respond well to physiotherapy and strengthening. Recurring dislocations or significant structural damage often need a procedure to repair and tighten the damaged tissue.
6. AC Joint Problems
The acromioclavicular joint connects the top of the shoulder blade to the collarbone. AC joint problems are common and often overlooked as a distinct cause of shoulder pain.
**AC joint injuries** (sprains or separations) typically happen from a direct fall onto the shoulder or onto an outstretched hand. They range from a mild sprain of the joint ligaments to a complete separation where the clavicle lifts visibly above the shoulder blade. The pain sits at the very top of the shoulder and is pinpoint — you can usually press on exactly the spot that hurts.
**AC joint arthritis** develops with age or after injury and causes a similar localised tenderness at the top of the shoulder, along with pain that tends to be worst when reaching across the body (crossing the arm in front of the chest). It's a common incidental finding on imaging in people over 40, though it doesn't always cause symptoms.
7. SLAP Tears and Labral Injuries
The labrum is a ring of cartilage that lines the socket and deepens it, giving the ball more to sit against. It also anchors the biceps tendon to the shoulder. A SLAP tear (Superior Labrum Anterior to Posterior) is a specific pattern of tear that starts at the top of the labrum and extends forward and backward.
SLAP tears are associated with two quite different mechanisms: a single acute injury such as a fall on an outstretched arm or a shoulder dislocation, or the cumulative effect of repetitive overhead throwing in cricketers, swimmers, and racquet sport players.
Symptoms can include a deep, catching pain in the shoulder, a sense of instability, weakness, and a popping or grinding sensation with certain movements. They can be difficult to diagnose on examination alone and often require MRI arthrography (an MRI performed with contrast injected into the joint) for confirmation.
8. Fractures
Shoulder fractures most commonly involve the clavicle (collarbone), the proximal humerus (the top of the upper arm bone), or the scapula (shoulder blade). Clavicle fractures are among the most frequent fractures overall, particularly in cyclists, rugby players, and those involved in motor vehicle accidents.
The mechanism and the patient's age both significantly influence treatment. In older patients, proximal humerus fractures often result from lower-energy falls — the same falls that cause wrist or hip fractures in osteoporotic bone. In younger patients, high-energy trauma is usually the cause.
Many fractures around the shoulder heal without surgery. When the bones are significantly displaced, or when the fracture involves the joint surface, surgical stabilisation is sometimes necessary to restore alignment and function.
9. Referred Pain
Not all shoulder pain originates in the shoulder itself. The neck (cervical spine) can refer pain into the shoulder and upper arm, and conditions such as a cervical disc herniation or nerve root compression can closely mimic shoulder pathology. The diaphragm shares a nerve supply with the shoulder (the phrenic nerve, C3–C5), which is why gallbladder problems and some other internal conditions can present as shoulder pain, typically on the right side.
This is one of the reasons a thorough clinical assessment matters — establishing where the pain actually comes from, rather than treating the location where it's felt.
When to See a Specialist
Most shoulder pain doesn't need to be investigated on day one — an acute muscle strain or minor sprain deserves a few days of rest and anti-inflammatories first. But shoulder pain is worth a specialist assessment if:
- It persists beyond two to three weeks with no improvement
- It follows a significant injury — a fall, a dislocation, a direct impact
- You're struggling to lift your arm, sleep on the shoulder, or do basic daily tasks
- You have numbness, tingling, or weakness in the arm alongside the pain
- You've had a previous shoulder problem and the pattern has changed
A precise diagnosis at the start saves weeks of treating the wrong thing. Book a consultation with Dr Andre Human (https://www.durbanorthopaedics.org/contact-us) at Specialist Orthopaedics Incorporated — we consult at Life Entabeni Hospital in Berea and at Hillcrest Hospital.
Author: Dr Andre Human — MBChB (PRET.), HDIP (ORTH)(SA), FCS(ORTH)SA. Shoulder and knee surgery specialist at Specialist Orthopaedics Incorporated, Durban. Active member of multiple surgical societies and ATLS Faculty Member, with over 15 years in private practice.'
**This article is for general patient education and does not replace a consultation with a qualified medical professional. If you are experiencing shoulder pain, please book an appointment for an assessment specific to your condition.**
Sources
- American Academy of Orthopaedic Surgeons, OrthoInfo — [Shoulder Pain and Common Shoulder Problems](https://orthoinfo.aaos.org/en/diseases--conditions/shoulder-pain-and-common-shoulder-problems/)
- American Academy of Orthopaedic Surgeons, OrthoInfo — [Common Shoulder Injuries](https://orthoinfo.aaos.org/en/diseases--conditions/common-shoulder-injuries/)
- American Academy of Orthopaedic Surgeons, OrthoInfo — [Frozen Shoulder](https://orthoinfo.aaos.org/en/diseases--conditions/frozen-shoulder)
- American Academy of Orthopaedic Surgeons, OrthoInfo — [Arthritis of the Shoulder](https://orthoinfo.aaos.org/en/diseases--conditions/arthritis-of-the-shoulder/)