Shoulder instability or dislocation occurs when the shoulder joint is forced out of its normal position, often leading to pain and loss of function.
The shoulder has the greatest range of motion of any joint in the body, a versatility that comes at the cost of comparatively limited bony stability. The socket is shallow, and the joint relies heavily on surrounding ligaments, the labrum and muscles to keep the ball centred during movement.
Dislocation describes the ball being completely displaced out of the socket, an acute and painful event, while instability describes a looser or recurrently unstable shoulder, which may involve full dislocations, partial dislocations known as subluxations, or simply a sense of the shoulder feeling like it might come out of place in certain positions.
Traumatic shoulder dislocation most often follows a fall, a sporting collision, or a direct blow that forces the arm into a position of abduction and outward rotation, levering the ball of the joint out of the socket. This is the most common mechanism, particularly in contact and collision sports.
After a first traumatic dislocation, the risk of further episodes is notably higher in younger patients, likely reflecting a combination of higher activity levels and the specific pattern of ligament and labral injury that occurs at a younger age. Some people also have naturally more flexible ligaments, known as hypermobility, which can predispose to instability without necessarily involving a specific injury.
Symptoms of an acute dislocation include:
For ongoing instability after a first dislocation, symptoms include:
An acute dislocation requires reduction, relocating the joint back into its normal position, typically performed in an emergency department. This is followed by X-rays and often further imaging such as an MRI to assess the labrum, ligaments and any associated bony injury.
After the acute episode, a period of relative rest and a structured physiotherapy programme focusing on rotator cuff and scapular strengthening is the usual first-line approach, particularly for a first-time dislocation.
For recurrent instability, or in younger, active patients after a first dislocation where the risk of recurrence is higher, surgical stabilisation may be recommended. This is most commonly arthroscopic stabilisation (Bankart repair), repairing the torn labrum and ligaments. Where there has been significant bone loss from the socket, a bone-block procedure such as the Latarjet procedure may be considered instead.
The risk of a further dislocation after a first traumatic episode is meaningfully higher in younger patients, which is an important factor in deciding whether to proceed with early surgical stabilisation versus a course of physiotherapy first. Surgical stabilisation generally provides good long-term shoulder stability and function, though, as with any surgery, it cannot completely eliminate the possibility of a future dislocation, particularly with further significant trauma.
Shoulder dislocation and instability reflect the trade-off between the shoulder's exceptional range of motion and its comparatively limited bony stability. Most first-time dislocations are treated with reduction, a period of rest and physiotherapy, while recurrent instability, particularly in younger patients, is often best managed with a structured strengthening programme and, where needed, surgical stabilisation. Following the rehabilitation programme after a first dislocation is one of the most important steps in reducing the risk of further episodes.
