The incredible elbow

At first glance the elbow seems like a fairly simple joint. It is a hinge joint and has roughly 160 degrees of movement.

However, when we consider that the same bones that interact at the incredibly mobile wrist interact at the elbow, the picture becomes more complex. In fact, the ability to twist the wrist really occurs at the elbow. Evaluation of the elbow is necessary to treat not only elbow problems, but wrist problems as well. The ability to have free, mobile hands and wrists requires stable healthy elbow joints.

There are three bones that articulate at the elbow. The largest bone is the upper bone that connects to the shoulder; the humerus. There are two bones in the forearm; the ulna (which is on the side of the pinky finger) and the radius (on the thumb side). The hinge of the elbow is easy to see, and occurs between the humerous and the ulna.

Hidden within the elbow is a second joint that allows the forearm to twist. This twisting can be palm up (supinate) or palm down (pronate).

This rotating joint is between the top of the radius and the ulna. This rotating joint allows the radius to twist around the ulna. No where else in the body does one bone twist over another – unless you cross your legs.

Articular cartilage caps the ends of our bones at the joints. Articular cartilage is white, shiny, and has a rubbery consistency. It is slippery, which allows the joint surfaces to slide against one another without causing any damage.

The function of articular cartilage is to absorb shock and provide an extremely smooth surface to make motion easier. In the elbow, articular cartilage covers the end of the humerus, the end of the radius, and the end of the ulna.

The ability to flex and extend the elbow is largely thanks to the biceps and triceps muscles. The biceps tendon attaches the biceps muscle to the radius. It is possible to feel the biceps tendon in the front of the elbow when you bend your elbow.

The triceps tendon attaches the triceps muscle to the back of the ulna. This powerful muscle is the source of power when straightening the arm.

Every power-lifter knows that to increase their bench-press weight they need to develop the triceps muscles.

The muscles of the forearm can be broken down into two groups. There are those muscles that bend the wrist and curl the fingers (Flexors) and those that extend the wrist and straighten the fingers (Extensors).

The Extensor muscles all share one tendon that attaches to a bump on the side of the humerous. Tendonitis of the extensor muscles tendon is the source of tennis elbow. Similarly, the Flexor muscles also share tendon that attaches to the other side of the humerous. Tendonitis of the flexor tendon is the source of Golfers Elbow, also known as Little Leaguer’s Elbow.

All of the nerves that travel from the neck down the arm must cross the elbow. Since the elbow bends and rotates the nerves must bend and twist as well.

There are three main nerves that cross the elbow; the radial nerve, the ulnar nerve, and the median nerve. Each of the nerves travels through its own tunnel as it crosses the elbow joint.

The constant bending and twisting of the elbow can lead to irritation of the nerves within their tunnels and cause pain, numbness, or weakness in the arm and hand.

The blood supply to the arm is provided by arteries that travel along with the nerves. The largest of these arteries is the brachial artery. The pulse of the brachial artery can be felt in the front crease of the elbow.

Damage to the brachial artery can be very serious as it is the only blood supply to the hand. Just below the elbow the brachial artery splits into the ulnar artery and the radial artery.

It is surprising just how complex the elbow is really. It allows both incredible stability and a large range of movement in multiple directions of not only the elbow but the wrist as well.

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