How does the elbow work?
The elbow joint is the site where the long bone at the top of your arm (the humerus) meets the two bones of your forearm (the radius and the ulna). It's a hinge joint, which means that you can bend your arm. The upper part of your radius can also rotate on the smooth surface of the capitellum, a part of your humerus, which helps you to twist your forearm.
The end of your humerus has two main bony parts which you can feel at the sides of your elbow. These are:
- the lateral epicondyle on the outside of your arm
- the medial epicondyle on the inside of your arm.
The lateral epicondyle is attached to the muscles involved in straightening (extending) your wrist and fingers. These extensor muscles are connected to your brain and nervous system primarily through your radial nerve, which travels on the outside of your elbow.
The medial epicondyle is attached to the muscles involved in flexing your wrist and fingers, which let you grasp objects. These flexor muscles are connected to your brain and nervous system primarily through your median nerve, which runs in front of your elbow.
Your ulnar nerve, which lies just below the medial epicondyle, is mainly responsible for the movements of the small muscles in your hand. These are useful for precise and delicate hand movements. If you hit your funny bone, you're pressing on your ulnar nerve.