Range of Motion
The shoulder is a ball and socket joint made up of three bones, namely the humerus, scapula and clavicle.
The end of the humerus or upper arm bone forms the ball of the shoulder joint. An irregular shallow cavity in the scapula called the glenoid cavity forms the socket for the head of the humerus to fit in. The two bones together form the glenohumeral joint, which is the main joint of the shoulder.
The scapula is a flat triangular-shaped bone that forms the shoulder blade. It serves as the site of attachment for most of the muscles that provide movement and stability to the joint. The clavicle bone or collarbone is an S-shaped bone that connects the scapula to the sternum or breastbone. The ends of all articulating bones are covered by smooth tissue called articular cartilage which allows the bones to slide over each other without friction enabling smooth movement.
Extra stability to the glenohumeral joint is provided by the glenoid labrum, a ring of fibrous cartilage that surrounds the glenoid cavity. The glenoid labrum increases the depth and surface area of the glenoid cavity to provide a more secure fit for the half-spherical head of the humerus.
The shoulder is also supported by soft tissues such as ligaments and muscles. The smooth movement of the shoulder is determined by the bones, joints, cartilage, ligaments, tendons and muscles.
Shoulder Range of Motion
The shoulder is the most flexible joint in the body, enabling a wide range of movements. The normal range of movement of the shoulder joint is the ability of the joint to move in various directions without difficulty or pain. These movements include:
- Forward flexion: lifting your arms forward
- Abduction: lifting your arms to the side
- Adduction: moving your arm towards your body, in the form of a hug
- Medial rotation: bending your elbow to 90 degrees and moving your palm towards your body
- Lateral rotation: bending your elbow to 90 degrees and moving your palm away from your body
- 360-degree circumduction: moving your arm in a circular manner – at 360 degrees
Conditions Affecting Range of Motion
The shoulder joint is considered the most insecure joint of the body but the support of ligaments, muscles and tendons function to provide the required stability. Some of the conditions that can affect the range of motion of your shoulders include:
- Sprains and Strains