Injuries and Conditions: Forearm and Elbow

Forearm
The forearm is located between the wrist and the elbow and contains two long arm bones, the radius and the ulna, which together form the radioulnar joint. The radius and ulna form a pivot joint, which is a joint that allows bones to rotate around one another. View illustrations.

The radius is a long arm bone that sits laterally to the ulna and extends from the inside of the elbow to the thumb side of the wrist. The lower end of the radius, or distal end, connects to the wrist and forms a significant portion of the wrist joint. The upper end of the radius connects to the elbow to form the elbow joint. The ulna is the larger of the two long arm bones and extends from the elbow to the wrist at the side opposite to the thumb. The ulna runs parallel to the radius, connecting to the humerus at the elbow to create a hinge joint.

The forearm can be divided into two compartments, the flexor compartment supplied by the median nerve and the extensor compartment supplied by the radial nerve - while the ulnar nerve runs the entire length of the forearm. The radial and ulnar arteries and their branches provide blood to the forearm.

Most of the muscles in the forearm run parallel to one another - originating near the elbow and extending to the tips of the fingers. The muscles located diagonally near the elbow and wrist facilitate the twisting motions of the forearm.

The flexor muscles, which are located on the palmer side of the forearm, allow the fingers to curl towards the palm. They also allow the action of lifting, grasping and holding, as well as bending of the wrist towards the palm. The extensor muscles are located on the opposite side and allow bending of the wrist towards the back of the hand.

Distal radius fractures are among the most common forearm injuries among athletes and average individuals alike, as outstretched arms are frequently used in many sports, shielding in an accident and in cushioning in a fall. These types of injuries should be carefully examined as there is often associated injury to the wrist joint, which, if undetected, could lead to an unstable joint and eventual joint degeneration.

Elbow
The elbow is located between the forearm bones (ulna and radius) and the upper arm humerus bone. Identified as a hinge joint, it is able to achieve flexion and extension - though only a limited amount of rotation.

Ligaments at the elbow joint work to assist in stabilizing the joint, which is surrounded and lined by articular cartilage that provides a cushion between bones and aides in movement. The ligaments, which connect bones to bones, form a joint capsule at the elbow joint - providing a lubricating synovial fluid.

Within the flexor and extensor compartments lay the muscles assisting movement and their corresponding nerve and vascular supplies. Biceps and triceps tendons work to provide elbow stability and function. The biceps tendon allows elbow bending and attaches the large biceps muscle to the radius at the front of the arm. The triceps tendon allows straightening and connects the large triceps muscle to the ulna at the back of the arm. The muscles of the forearm cross the elbow, attaching to the humerus at the outer or lateral side of the elbow. This is often the source of lateral epicondylitis, or tennis elbow.

The apparent "bump" located to the outside of the elbow is called the lateral epicondyle, which is where most of the muscles responsible for straightening the fingers and wrist meet - attached by one tendon. The inside or medial portion just above the elbow is called the medial epicondyle, where most of the muscles that bend the fingers and wrist come together. This is often the site of medial epicondylitis, or golfer's elbow.

Working together to connect and stabilize the arm bones are the medial collateral ligament (MCL), the lateral collateral ligament and a network of tendons. The medial and lateral collateral ligaments provide the main source of stability for the elbow.

The ulnar nerve that travels down the arm allows bending motion and assists in the sensation and movement of the hand and wrist. The nerve passes through the cubital tunnel, which is a tunnel of bone, muscle and ligament located just inside the elbow joint. As a result of the bending motion the elbow joint can achieve this is often the site of a common elbow condition called Cubital Tunnel Syndrome. This is often confused with Golfer's Elbow, also known as medial epicondylitis, as a result of the location and similarity of symptoms.

The amount of activity that the elbow joint experiences in day to day and sports activities, combined with the large number of tendons and nerves passing through and located within the joint make it vulnerable to injury and many common overstress conditions.