The Unstable Shoulder – with Lewis Craig
The Unstable Shoulder – When Your Shoulder Doesn’t ‘Feel Right’
Shoulder Instability describes a group of conditions where there is loosening of the connective tissue surrounding the shoulder joint. This results in excessive movement within the joint leading to pain, apprehension or the shoulder ‘just doesn’t feel right’ with particular movements. An unstable shoulder can present following an acute traumatic incident or progressively over time due to repeated stresses on the joint.
Anatomy
The shoulder is a ball and socket joint, similar to a golf ball on a golf tee the humerus (ball) sits within the glenoid cavity of the shoulder blade (socket). To provide support to this joint are three major ligaments, the superior, middle and inferior glenohumeral ligaments, which form the joint capsule. Additionally the rotator cuff muscles provide support for the shoulder joint, particularly during movement and loading. Injury to the joint capsule or surrounding supporting musculature can allow the humerus to move excessively within the glenoid cavity, leading to feelings of instability or apprehension with shoulder movement.
Causes
An unstable shoulder can present either from a traumatic event or atraumatic. Atraumatic instability is due to repetitive joint stresses over time, particularly with throwing sports or those with overhead activities, such as water polo, cricket or swimming. The majority of shoulder instabilities are secondary to an acute traumatic incident in which excessive stress to the shoulder joint results in either shoulder dislocation or partial dislocation, termed a subluxation. This results in injury to the joint capsule, surrounding rotator cuff muscles and or the joint surface (including, cartilage, labrum and bone). The injury is usually in a position of abduction (side elevation) and excessive external rotation (outer rotation of the humerus) (see image below) combined with a force to the back of the shoulder, front of the elbow or hand, or both. This forces the head of the humerus anteriorly (forwards), stressing the front of the joint capsule. This results in an anterior instability. Shoulder instabilities can also be classified as posterior instability or multidirectional instability.
Signs and Symptoms
An unstable shoulder may present with little or no pain at all. In many cases, an individual will describe feelings of apprehension or unsteadiness in a particular position, with a certain movement or during an exercise. If the shoulder pain is a result of a traumatic event, it can be accompanied by significant pain localised to the shoulder and reduced shoulder movement. With an acute anterior shoulder dislocation there will also be a prominent forward and inferior position of the humerus. For unstable shoulders without a clear moment of injury special orthopaedic testing by your physiotherapist will also help to confirm diagnosis and type of instability. In some circumstances higher load activities and movements may be needed to reproduce your symptoms for diagnosis and management.
Management
Any shoulder dislocation is a medical emergency. A trained medical professional should reduce the dislocation as soon as possible. This will be greatly beneficial for pain relief and ensure that the shoulder is in correct position and without injury to the axillary nerve or blood vessels. It is important for all first time dislocations to be x-rayed after reduction to rule out bony injury to the glenoid cavity or humerous, termed bankart or hill-sachs lesions. Following an acute dislocation the shoulder will undergo a period of immobilisation in a sling and consultation with an orthopaedic surgeon may be required. Rehabilitation for shoulder instabilities will focus on a progressive motor control and strengthening program for rotator cuff muscles. Surgical management may be indicated if the shoulder undergoes continual subluxations or dislocations or is not responsive to conservative management.
Lewis Craig (APAM)
POGO Physiotherapist
