The shoulder comprises three bones – the humerus (bone of the upper arm), the scapula (the shoulder blade) and the clavicle (the collarbone) – which are connected at the shoulder joint (the 'glenohumeral joint') with a ball joint where the ball at the top of the humerus (called the 'head' of the humerus) fits into the socket (the 'glenoid cavity') of the scapula.
The entire joint is contained within a capsule comprising an inner and outer membrane. Making up the components of the joint are the associated muscles and ligaments, nerves and blood supply, a layer of cartilage cushioning the ball and socket and small fluid filled sacs called 'bursae' which act as cushions allowing muscles and ligaments to move smoothly.
All of these components work together to give a wide range of motion to the arm, however problems can develop in the shoulder joint which can cause pain and restrict this range of motion.
The most common conditions affecting the shoulder include:
It is relatively common for arthritis to develop in the shoulder which can in turn cause pain and restrict the range of movement of the arm.
Rotator Cuff Tears
Cuff tears are tears that affect the muscles and tendons that work the shoulder joint, known collectively as the 'rotator cuff', which can in turn cause pain and weakness in the affected arm.
Shoulder Dislocation and Instability
Shoulder dislocation is the term that describes cases where the head of the humerus (the ball joint) comes away from its socket. Shoulder dislocations can thereafter cause shoulder instability.
Shoulder Tendon Pain
It is fairly common to develop tendon pain in the shoulder, sometimes referred to as 'shoulder tendinopathy'.
Frozen shoulder is a painful and debilitating condition where the shoulder can stiffen, and it can be very difficult to move the shoulder without pain. The condition can last for a long time.
Shoulder trauma describes any moderate to severe injury to the shoulder, most often from accidents or when playing some sports.