The shoulder is an incredible joint. It has near 360° range of movement, allowing one to place the upper limb virtually anywhere in space. This enables us to throw, perform overhead movements and manipulate tools.
Having sacrificed brute strength for mobility, the shoulder joint exhibits the greatest range of movement in the body: it flexes, extends, abducts, adducts, rotates internally and externally as well as circumducts.
This trade-off requires the shoulder to rely heavily on soft tissues for stability (i.e. muscles, cartilage, tendons and ligaments). Its subsequent diminished natural stability makes it more prone to slipping, straining, or dislocating during sport and daily activities.
Why the Shoulder Is So Unique
The shape of the joint plays a big role in its extreme mobility. The shoulder uses a ‘concavity-compression’ mechanism – generated by the Rotator Cuff – to keep the humerus in its shallow socket – a joint formed between the glenoid (the saucer-like joint surface of the scapular) and humeral head.
This complex mechanism, often compared to a golf ball balancing on a tee, allows free movement, but is not built for stability.
Because of this structure, shoulder health depends heavily on the soft tissues around the joint rather than the bone shapes themselves.
The Team That Keeps the Shoulder Stable
Several structures work together to keep the “ball” centred on the “socket”:
- The Labrum is a ring of cartilage that deepens the glenoid and helps the joint stay secure.
- The Capsule and Ligaments are a sleeve of connective tissue that supports the joint and both allows flexibility and function while preventing excessive movement.
- The Rotator Cuff Muscles are four small but important muscles that steer and stabilise the shoulder during every movement.
- The Scapula (Shoulder Blade) is the foundation of the shoulder joint and affects strength, control, and overhead comfort.
What Happens During a Shoulder Dislocation?
A shoulder dislocation occurs when the ball comes completely out of the socket. This often happens during high-force movements such as a rugby tackle, a fall onto an outstretched arm, or an awkward landing during sport.
Most dislocations (92%) result in displacement of the head of the humerus completely out of the joint and sits forward of the glenoid — known as an anterior dislocation.
Common related terms include:
- Dislocation — the ball fully leaves the socket.
- Subluxation — the ball partially slips out and returns on its own.
- Labral tear— the cartilage around the glenoid can be damaged during a dislocation (medically known as a Bankart lesion).
- Hill-Sachs lesion — is a fracture caused by the traumatic contact between the humeral head and glenoid after a dislocation. The fracture occurs on the head of the humerus.
- Instability — the feeling that the shoulder is loose, unreliable, or likely to slip again.
These terms simply describe the different ways the shoulder responds to excessive force or repeated stress.
Why Some Shoulders Dislocate More Easily
Several factors increase the chance of recurrence:
- Age: Young and active individuals, especially teenagers, have higher rates of repeated instability.
- Activity level: Sports with tackling, overhead movements, or rapid direction changes carry a higher risk.
- Joint flexibility: Naturally flexible shoulders may be more prone to slipping or strain.
Scapular dyskinesia
The scapula acts as the foundation of the shoulder joint and is the base upon which the glenoid arises.
When the scapula moves normally, it keeps the shoulder well-aligned and the rotator cuff working efficiently. Scapular dyskinesia – abnormal or uncoordinated scapular movement – disrupts this foundation.
It alters the position of the glenoid, decreases stability, causes weakness and places extra strain on the ligaments and rotator cuff. As a result, the humeral head is less well-contained, making the shoulder more vulnerable to slipping or dislocating, especially during overhead or high-demand activities.
Scapular dyskinesa, even when sublte, can present as instability and shoulder pain.
Scapular stability is mandatory for preventing impingement, maintaining joint congruency and generating power.
Early Detection: Why Small Symptoms Matter
Common early indicators of instability or soft-tissue stress include:
- A feeling that the shoulder may “give way”
- Recurrent clicking or catching
- Sharp pain during lifting or throwing
- Weakness after a fall or awkward movement
- Loss of overhead confidence
These symptoms don’t always mean a serious injury, but they do suggest the shoulder is working harder to stay stable.
How Shoulder Instability Is Managed
Management usually focuses on:
- Restoring movement
- Supporting healthy scapular mechanics
- Improving rotator cuff and stabiliser strength
- Building control before returning to sport
Some individuals experience repeated dislocations or persistent instability.
While care is always individualised, in many cases of shoulder instability, further investigation may be recommended to both confirm the underlying cause of dysfunction and provide guidance regarding both surgical and non-srugical management options.
Shoulder Stability in South African Sport
From rugby and cricket to swimming, padel and netball, South African athletes rely heavily on shoulder strength and coordination. Many shoulder problems begin with small changes — discomfort during overhead movements, loss of control after a tackle, or stiffness following a fall.
Recognising these early signs supports better outcomes and helps maintain an active lifestyle through the season.
Final Thoughts
The shoulder is built for movement, not stability. Its design allows for remarkable flexibility, but this also means it relies on a delicate balance of muscles, ligaments, and coordinated movement to stay healthy.
Understanding how shoulder stability works — and noticing early changes — can help protect this complex joint for years to come.
While this article briefly explores shoulder stability and important warning symptoms, it is only intended for general informational purposes and should not be used as a substitute for professional medical advice.
This article is intended solely to support general awareness and promote healthy decision-making around shoulder health and joint care. Should you, or someone you know, wish to seek professional medical advice, one is strongly urged to consult a qualified healthcare provider, or contact Dr Maina’s rooms, for an in-person assessment for guidance specific to your health.
Dr Anne Maina
FC Orth (SA), MMed Ortho (Wits), MBBCh (Wits), CIME
