Scapula Anatomy

What is the Scapula?

The scapula is a vital component of the shoulder girdle. This triangular-shaped bone makes up half of the main shoulder joint, called the Glenohumeral Joint, and allows for the extremely high ranges of motion possible at the shoulder. The shoulder is classically called a ‘Ball and Socket’ joint, but in reality, is more like a ‘Golf Ball and Tee’ joint. A major part of the scapula is the Glenoid Cavity, one half of the shoulder joint. This extremely shallow cavity is where the head of the Humerus sits to form the shoulder, the head of the Humerus is the golf ball, and the Glenoid cavity is the Tee. This is not a stable joint on its own.

The shoulder can move in nearly in any direction. This is because, in the human’s natural habit such as the African Savannah, the shoulder was used for throwing, carrying and balance during locomotion, so it needs to be highly mobile. However, the shoulder joint is actually not that mobile on its own. The scapula plays a huge role in the overall mobility of the shoulder. When the shoulder joint moves, in this example in Frontal Plane Abduction, it actually gets stuck as the head of the Humerus collides with structures such as the Acromion and the Coracoacromial ligament. This limitation stops the shoulder joint before it even reaches 90° of abduction in most cases, not exactly a range of motion worthy of the bodies most mobile joint.

What does the Scapula do?

Incomes the scapula, this bone is free to slide and glide over the thoracic ribs. This is often called the Scapulothoracic joint, this is a false joint however as the scapula and thoracic do not share direct contact. The scapula aids the shoulder joints range of motion by upwardly rotating across the thoracic ribs, this movement allows the arm to be raised well above the head.

This can be demonstrated yourself. Try to raise your arms out to the sides and overhead. Now try and do the same thing while trying to squeeze your shoulders together like you’re holding a pencil between your shoulders. I’d be willing to assume you got your hands overhead more so in the first attempt. This is because the scapula gives the shoulder so much more range of motion, and without a free moving scapula the range of motion at the shoulder would be quite pathetic.

For swimmers

Scapula movement is essential in swimming performance and avoiding shoulder injuries. Neglecting the movement of the scapula can lead to increased demands on the tissues of the shoulder such as the capsule, rotator cuff and surrounding musculature, overtime this can lead to shoulder, neck, arm and back pain, reduced ranges of motion, limited motor control and drop out from swimming.