What is the scapula and what does it do?
The body has 206 bones that make up the skeletal system at adulthood. Some of them are the stereotypical bone shape that you might think of if I asked you to picture a bone in the body. You might picture something like the long bone in the thigh, the femur. But there are also lots of bones in unique shapes that contribute to all the variability in movement that we can do. One of these unique bones is the scapula.
The scapula is one of the bones that makes up the shoulder complex. We have two of them — one on each side of the upper part of the back. Each scapula is a roughly triangular-shaped bone that is important for connecting the arm to the torso. The largest section of the bone is located posterior to the ribcage, but each scapula has two bony arms that curve around anteriorly and are part of the shoulder girdle.
Bony landmarks of the scapula
Important bony landmarks on the scapula include:
- Coracoid process
- Spine of the scapula
- Superior angle
- Inferior angle
- Lateral border
- Medial border
- Supraspinous fossa
- Infraspinous fossa
- Glenoid cavity
Muscles that attach to the scapula
The scapula bone is an important site for muscle attachment. There are 17 muscles that attach to the scapula! Muscles that attach to the scapula include the following:
- Serratus anterior
- Teres minor
- Teres major
- Rhomboids major
- Rhomboids minor
- Levator scapulae
- Pectoralis minor
- Triceps brachii
- Biceps brachii
- Latissimus dorsi
The scapula connects with other bones at the:
- Acromioclavicular joint = where the acromion of the scapula meets the clavicle
- Glenohumeral joint = where the humerus meets the glenoid fossa of the scapula
- Scapulothoracic joint (a false joint) = although the scapula “floats” on the ribcage and does not connect with the ribcage in the way that we usually describe bones connecting at a joint, the area where the scapula meets the ribcage is sometimes referred to as the scapulothoracic joint.
Movements of the scapula
Due to its shape, orientation, and the mobility of the joints where the scapula meets other bones, it has a unique suite of possible movements. They include:
- Elevation = scapula moves upward
- Depression = scapula moves downward
- Retraction (also called adduction) = scapula moves closer to the spine
- Protraction (also called abduction) = scapula moves away from the spine and around toward the front of the ribcage
- Downward rotation = scapula rotates around a central axis to bring the inferior angle closer to the spine
- Upward rotation = scapula rotates around on its central axis to bring the inferior angle away from the spine
- Posterior tilt = the medial border of the scapula lifts off the ribcage
The scapula is a unique bone in the body and contributes to the wide range of movements that we can access at the shoulder girdle. If you’d like to learn more, check out our article on the shoulder girdle.