The joints of the forearm are the distal radio-ulnar joint, and the interosseous membrane of the forearm.

Figure 1. The joints of the forearm (Credit: OpenStax, CC BY-SA 4.0)

Distal radio-ulnar joint

The distal radio-ulnar joint is a pivot type of synovial joint (diarthrosis), made up of the articulation between the articular surface of the head of the ulna, the ulnar notch of the distal end of the radius, and a fibrous articulating disc, separating this joint from the wrist joint.

Movement

The distal radio-ulnar joint facilitates two movements, together with the proximal radio-ulnar joint -- pronation, and supination.

Muscles

There are four muscles involved in the pronation and supination of the forearm, along with one stabilizer muscle. Two muscles are supinators, and two muscles are pronators.

  • Supinators:
    • Biceps barchii: The largest of the supinators. Supination is most effective when the forearm is flexed.
    • Supinator muscle: Located in the posterior compartment of the forearm, and has a wide origin.
      • Its tendon, together with the biceps brachii tendon, wrap around the distal end of the radius

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