The elbow joint is made up of 3 articulations: Humero-Ulnar joint (main one), Humero-Radial joint and the proximal Radio-Ulnar joint. While the Humero-Ulnar(mainly) and Humero-Radial joints are designed to provide Flexion and extension (bending and straightening) of the elbow the proximal (upper) Radio-Ulnar joint provides supination and pronation (rotation) of the forearm.
The elbow serves as the origin of muscles which are responsible for moving the wrist. The Lateral (outer) surface serves as the origin of the muscles that extend the wrist forming what is known as Common Extensor Origin”. The Medial surface serves as the origin of the muscles that Flexes ( bends) the wrist forming the “Common Flexor Origin”.
Both of these origins are common sites to Tendinitis and Tendinopathy as seen in Tennis Elbow and Golfer’s Elbow.
