The scapula bone forms part of the shoulder girdle and sits on the posterior chest wall. It forms part of the glenoid (socket) in the glenohumeral joint. The scapula moves a significant distance in normal shoulder movement and forms the scapulothoracic joint.
Pain around the scapula is common and can be referred from other sites such as the neck, thoracic spine or shoulder itself. The muscles that stabilise the scapula can be a source of pain in problems of the shoulder and neck. These muscles can fatigue leading to local discomfort and loss of the normal scapula control.
There is a bursa which eases the gliding between the shoulder blade and chest wall. This can be inflamed usually leading to pain and noisy movements. This has been referred to as ‘snapping scapula’ and can also occur secondary to extra bone the undersurface of the scapula (which is very rare).
The other main area of scapula problems can be grouped together as ‘winging of the scapula’. This is where the surrounding muscles become dysfunctional. This results in the shoulder blade sticking out and not moving properly. This can have a secondary effect on fatigue of the rotator cuff leading to shoulder pain.
Causes of winging
This is where the nerve supply to some of the muscles is affected with the most common being that the long thoracic nerve stops working. This supplies the muscle serratus anterior which causes the shoulder blade to stick out.
Another pattern is where the trapzius muscle stops working and this is associated with problems affecting the accessory nerve.
There is a muscular dystrophy called fascia-scapulo humeral dystrophy. This is a progressive disorder resulting in muscle weakness affecting facial muscles and muscles around the scapula.
Secondary to pain and instability
The winging that occurs secondarily tends to be less severe than the neurological causes. This will be usually correctable by skilled physiotherapy.