Glenohumeral Joint

The glenohumeral joint is a ball-and-socket synovial joint and is the most mobile joint in the human body. The joint is where the shoulder blade (scapula) meets the upper arm bone (humerus). This is a ball-and-socket joint. The socket (glenoid) is shallow, so it relies on the muscles and tendons around the shoulder to keep the ball (humerus) in place.

The glenohumeral joint is the most mobile joint in the body, allowing the arm to move in a wide range of motion. However, this increased mobility also makes the joint less stable, which can lead to dislocation or other injuries.

The glenohumeral joint is a synovial joint. This type of joint has a thin layer of tissue (synovium) that produces a small amount of fluid. This fluid lubricates the joint and helps to reduce friction. The synovium also provides nutrients to the cartilage and removes waste products from the joint. A synovial joint is the type of joint found between bones that move against each other, other examples include the hip, elbow and knee.

Ligaments of the glenohumeral joint

The capsule of the glenohumeral joint is a fibrous sheath that surrounds the joint and is attached to the margins of the articulating surfaces. The capsule is reinforced by a number of ligaments, which function to provide stability to the joint.

The four main ligaments of the glenohumeral joint are:

Superior glenohumeral ligament (SGHL)

The SGHL is a strong ligament that runs from the superior margin of the glenoid cavity to the lower margin of the neck of the humerus. This ligament provides support to the joint by preventing posterior displacement of the head of the humerus.

Inferior glenohumeral ligament

The inferior glenohumeral ligament attaches the lower part of the shoulder blade (scapula) to the upper part of the arm bone (humerus)

Anterior Band of the Superior Glenoid Labrum

The glenoid labrum is a ring of cartilage that surrounds the socket (glenoid) and deepens it, providing additional stability to the joint.

The Anterior Band of the Superior Glenoid Labrum is a thickened band of tissue that runs from the anterior margin of the glenoid cavity to the lower margin of the neck of the humerus. This ligament provides support to the joint by preventing posterior displacement of the head of the humerus.

Posterior Band of the Superior Glenoid Labrum

The Posterior Band of the Superior Glenoid Labrum is a thickened band of tissue that runs from the posterior margin of the glenoid cavity to the lower margin of the neck of the humerus. This ligament provides support to the joint by preventing anterior displacement of the head of the humerus.

Muscles of the Glenohumeral Joint

The muscles and tendons around the glenohumeral joint are responsible for moving the arm. These include the:

Rotator cuff muscles

The rotator cuff muscles attach the shoulder blade (scapula) to the upper arm bone (humerus). They include the supraspinatus, infraspinatus, teres minor, and subscapularis. The rotator cuff muscles help to lift the arm.

Biceps muscle

This muscle attaches the shoulder blade (scapula) to the upper arm bone (humerus) and the collarbone (clavicle). The biceps muscle helps to lift the arm.

Triceps muscle

This muscle attaches the shoulder blade (scapula) to the upper arm bone (humerus). The triceps muscle helps to extend the arm.

Pectoralis major muscle

This muscle attaches the breastbone (sternum) to the shoulder blade (scapula). The pectoralis major muscle helps to lift the arm.

Latissimus dorsi muscle

This muscle attaches the lower back (lumbar spine) to the shoulder blade (scapula). The latissimus dorsi muscle helps to lift the arm.

Deltoid muscle

The deltoid muscle is a large, triangular muscle that covers the shoulder joint. It attaches the shoulder blade (scapula) to the upper arm bone (humerus) and the collarbone (clavicle). The deltoid muscle is responsible for lifting the arm. The Anterior Deltoid moves the arm upward in front of the body (Flexion). The Medial deltoid moves the arm up to the sides of the body (Abduction). The Posterior Deltoid moves the arm up behind the body (Extension).