The shoulder is a complex and highly mobile joint that plays a crucial role in our daily activities. It consists of several key components, including the humerus (upper arm bone), scapula (shoulder blade), and clavicle (collarbone), as well as various muscles, ligaments, and tendons. Understanding the anatomy of the shoulder is essential for diagnosing and treating common injuries that can affect this region.
The shoulder complex itself is made up of four separate joints, and each can have individual or overlapping issues, resulting in pain, swelling/ inflammation, loss of strength/range of motion and function.
Glenohumeral – Where the rounded head of the humerus sits meets the shoulder blade, and is stabilized by a shallow socket known as the labrum. Common injuries include osteoarthritis, labral tears, SLAP lesions, biceps and supraspinatus muscle tendinopathies, rotator cuff tears, or strains, external or internal impingement, calcific tendonitis or repetitive strain injuries, dislocations and subluxations.
Acromioclavicular – Commonly known as the AC joint, this is where your collarbone aka clavicle, comes into contact with the top of your shoulder blade. This is an area of common injury, as the glenohumeral joint is just below, and all the muscles of the rotator cuff attach under the acromion. Common injuries include AC joint sprains, osteoarthritis, rotator cuff sprains and strains, separations, dislocations and subluxations.
Scapulothoracic – This Is where the shoulder blade sits on the back of your ribs. Did you know, seventeen muscles attach to the shoulder blade, and all are needed to work in sequence to raise your arm above your head? This sequence of muscle activation while raising your arm, is often known as your ‘Scapulothoracic Rhythm.’ In order to allow your arm to raise above your head, your shoulder blade first rotates, clearing space for your arm to raise above your head without pinching muscles between your arm and your shoulder blade. This ideally means we want our shoulders straight, not rounded, so our shoulder blades can sit flat and ride smoothly against our ribs as we raise our arms. Common injuries include: winging scapula, snapping scapula, thoracic kyphosis, scoliosis.
Sternoclavicular – This is where your clavicle meets your chest. You may not notice often, but your clavicle rotates backwards as your arm raises, again to allow space for muscles to not get pinched at the AC joint. Common injuries include joint separations, sprains and strains, and osteoarthritis.
Common shoulder injuries often include:
- The rotator cuff: overuse, trauma, or degeneration
- Rotator cuff tears
- Shoulder dislocations and instability
- Tendonitis
- Impingement syndrome
- Frozen shoulder/adhesive capsulitis
- Labral tears
- Sternoclavicular joint injury
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