The elbow joint connects the upper arm and the forearm. It is one of the body’s most frequently used joints, and many important structures pass through or around it. The elbow contains a large amount of lubricating liquid (which is, sadly, not called elbow grease). This lubricant allows the elbow to make smooth, precise movements even when it is bearing a substantial weight load.
The joints in the upper body correspond with those in the lower body: shoulders have a similar structure to hips, wrists have similar functions as ankles, and elbows correspond with knees.
Movements of the Elbow
Elbows help put the hand in space properly, and allow the arm to engage in two pairs of opposing motions:
● Flexion (e.g., touching your fingers to your shoulders)
● Extension, the opposite of flexion (dropping your hands towards your legs)
● Supination (turning your thumbs away from your body)
● Pronation, the opposite of supination (turning your thumbs toward your body)
The Bones of the Elbow
Three bones meet at the elbow:
● One upper arm bone coming down from the shoulder called the humerus;
● One slightly larger lower arm bone extending to the little finger called the ulna;
● One slightly smaller lower arm bone extending to the thumb called the radius.
The bony center of the elbow that you can feel is the head of the ulna, also called the olecranon. The bony landmarks just to the inside and outside of it are the ends of the humerus. They are attachment points for muscle tendons and are called epicondyles.
The Joints of the Elbow
Elbows are primarily hinge joints, allowing the forearm to swing along one plane of motion like a door. However, there are actually three joints at the elbow:
● one where the humerus and the ulna connect;
● one where the humerus and the radius connect;
● one where the radius and ulna connect.
The humerus-ulna connection provides the hinge joint.
The humerus-radius connection is technically a ball-and-socket joint. Still, its motion isn't as free as other ball-and-socket joints like shoulder and hip because a ligament binds the two forearm bones together and restricts their movement.
The radius-ulna connection is a pivot joint, allowing for one bone to moderately rotate inside of the space of another, a bit like the wash cycle of a washing machine.
The Muscles of the Elbow
The biceps are the muscles that help flex the elbow. When your biceps contract, they pull your forearm towards your upper arm and shoulder. The biceps are assisted by two deeper muscles called the brachialis and brachioradialis muscles. The biceps also helps supinate, or turn, your hands palm side up.
The triceps are the muscles that help extend, or straighten, the elbow.
Pronation, or turning palm side down, is controlled mainly by forearm muscles that do not cross the elbow. Those muscles are considered those of the hand/wrist.
The Connections of the Elbow
Like all joints, the elbow is held together by tendons and ligaments. Tendons are stretchy and attach muscles to bones. Ligaments are tough and connect bones to each other. Two important ligaments of the elbow are the ulnar collateral ligament and the annular ligament.
The elbow gets its blood supply from a large artery called the brachial artery, which branches out like an irrigation system to ensure the elbow gets a full supply. There are several different nerves of the elbow, too, including the median, radial, and musculocutaneous nerves.
The one you might know best is the ulnar nerve at the back of the elbow; when you hit it accidentally, it causes the "funny bone" sensation and can be felt all the way down to the tip of your pinky finger!
The Health of the Elbow
Our elbows get plenty of use throughout the day. Certain movements repeated over and over again can often cause pain or soreness, especially in the world of sport. In fact, two common elbow injuries are named due to their prevalence in players of specific sports:
- Golfer's Elbow: caused by the over-stretching of the tendons if the flexor muscles at the medial epicondyle (i.e., the inside of the elbow)
- Tennis Elbow: caused by overworking the tendons of the extensor muscles at the lateral epicondyle (i.e., the outside aspect of the elbow)
Throwing a baseball at high velocity puts large torque forces on the ulnar collateral ligament on the inside aspect of your elbow. (Refresher: that's the ligament that connects your humerus to your ulna). Thus, ulnar collateral ligament damage is common in baseball pitchers. If the ligament tears, it often requires ulnar collateral ligament reconstruction, popularly known as Tommy John surgery after the 1970s pitcher who first underwent the procedure.
The fluid-filled sac at the olecranon (the bony center) of the elbow can get inflamed, red, warm, and swollen. This condition is called olecranon bursitis. It is often managed by draining the excess fluid from the elbow with a needle.
With three bones meeting at the elbow, fractures are fairly common, especially from falls. X-rays can help rule fractures out.
Knowing about the structure and functions of joints like your elbows can help you utilize them properly to meet your exercise and fitness goals.