Shoulder Impingement refers to the intermittent entrapment or pinching of one of the rotator cuff tendons on shoulder movement, in particular reaching overhead or behind your back. This causes injury to the tendon and occasionally, the bursa (a fluid filled sac that provides cushioning between a tendon and bone) sitting underneath it. Causes of shoulder impingement include trauma (a direct fall onto the shoulder), overuse or poor posture and biomechanics. Some sufferers can be genetically predisposed to the condition due to bony abnormalities in the shoulder joint, such as bony spurs or ridges.
Rotator Cuff Tears
The rotator cuff is made up of a group of 4 muscles. Their job is to help stabilise the shoulder and to produce the rotation movements of the shoulder. Tears can occur within the muscles and their tendons from trauma or from overuse, gradually forming over time. Occasionally spontaneous tears can occur in the older population, especially those who have taken high doses of steroid medication over the years. If the muscle is completed ruptured, sometimes very little pain can be felt. The main symptom of a rotator cuff tear is reduced mobility in the shoulder, particularly on reaching overhead or out to the side (abduction).
Acromioclavicular (AC) joint injury
The acromioclavicular joint is the joint formed between the end of the clavicle (collarbone) and the acromion (the tip of the shoulder blade). It is commonly injured by either a direct fall onto the point of the shoulder or a fall onto an outstretched hand, two common falls for a horse rider. The ligaments that hold the joint together can either stretch, partially tear or completely tear. In those with a more severe tear, a notable lump will be seen on the top of the shoulder. In this case the ligaments that bind the clavicle and acromion together have torn, causing the end of the clavicle to lift.
Frozen Shoulder (Adhesive Capsulitis)
Frozen shoulder or adhesive capsulitis, is a thickening of the joint capsule and ligaments of the shoulder, causing pain and a restriction of movement. There is no known cause of frozen shoulder, although it is more common in middle aged women and in diabetes sufferers. The condition goes through 3 distinct phases: freezing, frozen and thawing. The freezing stage is characterised by increasing pain and continual loss of movement. In the frozen phase the pain typically subsides and there is no further loss of range, but no improvement either. The thawing stage is when the injury starts to resolve, with an increase in shoulder movement. There is often residual weakness following this last stage. Frozen shoulder can last for up to 18 months.
The shoulder is a common site of referred pain from the neck or thoracic spine (mid back). Pain that is felt across the back of the shoulder is commonly referred pain.