How is the shoulder joint structured?

The shoulder joint consists of the following bone structures:

  • the head of the humerus: spherical end of the humerus
  • the glenoid cavity: shallow concave surface on the shoulder blade
  • the acromioclavicular joint: connection to the clavicle
Anatomy Shoulder Joint

When in a healthy condition, both joint surfaces are covered with a layer of joint cartilage, that acts as a shock absorber, distributes and reduces the forces acting on the shoulder joint. The synovial fluid is a gel-like substance that lubricates the joint and enables a smooth movement of the joint and reduces friction. The shoulder is the most mobile joint in the human body, and is therefore referred to as a primarily muscle.

Role of the joint capsule and rotator cuff

The shoulder joint is surrounded by a fixed joint capsule, which seals it off from the surrounding tissue. This produces ‘synovial fluid’, which enables the shoulder joint to move free from friction and also supplies the cartilage with nutrients.

Stability and movement thanks to muscles

The spherical head of the humerus is only held very loosely in the small, shallow glenoid cavity of the shoulder blade. For this reason, muscles tendons and ligaments play an important role in stabilising the shoulder joint, while keeping it as mobile as possible. This is mainly achieved by a complex group of muscles known as the rotator cuff. This consists of four muscles which surround the shoulder joint like a cuff, protect it and enable the arm to move. Another important muscle here is the bicep. In addition to the muscles, tendons and ligaments also support the range of movement.