The scapula (shoulder blade) is a triangular shaped bone which sits on the back of the upper body functionally providing a link between the upper limb and the rest of the body.

The scapula has minimal connection to the body via bones and joints; the clavicle (collar bone) being the only such connection; instead it connects via muscles that run from the scapula to the trunk, middle back, and neck, and the resting position of the scapula is dictated by the relative balance (in terms of muscle length and tone) between these muscles.

These muscles have an important role in both stabilising the scapula onto the trunk, but also in moving and re-orientating the scapula in conjunction with movement of the upper limb, especially overhead movements, thus providing a stable yet mobile base for the shoulder and upper limb to function upon.

When we move our arm, such as to reach overhead, these muscles move the scapula so that the socket of the shoulder joint is always pointing and facing in a similar direction to that of the upper limb. This mechanism is vital for shoulder joint stability as it means that the humeral head (ball) is always centred in the socket wherever the arm is in space thus helping to prevent dislocation of what is inherently an unstable joint.

Problems arise when for various reasons the scapula stabilising muscles fail to work correctly. Shoulder impingement can develop when the scapula fails to ‘follow’ the arm resulting in soft tissues of the shoulder impinging against part of the scapula with shoulder movement. Shoulder instability can also result as the humeral head centring mechanism described above fails. Other injuries around the shoulder can also develop as alterations in the mechanics of the shoulder complex leads to increased stress on other tissues in the region with continued activity.

Video of scapula instability with e.g. shoulder flexion

Abnormal scapula control is also associated with neck pain and cervicogenic headaches. Alterations in scapula movement or resting position places increased strain on those scapula muscles that attach to the head and neck, often directly pulling the head / neck into adverse postures. This is especially common in those with poor workstation / desk ergonomics where the long lever arm resulting from excessive and sustained positions of reaching to mouse / keyboard pulls the scapula into a poor position.

Correction of any abnormality of scapula position or movement is achieved with specific exercises to first learn to correct the neutral resting position, moving on to exercises aiming to maintain correct alignment of the scapula with small movements of the arm, before finally progressing onto exercises focusing on keeping scapula alignment with movements against load (e.g. weights) and with speed.