Proximal radioulnar joint | The elbow joint

Proximal radioulnar joint

In the proximal radioulnar joint (Articulatio radioulnaris proximalis), the edge of the radial head (Circumferentia articularis radii) and the corresponding notch on the inner side of the ulna (Incisura radialis ulnae) are joined together in an articulated manner. They form a wheel joint which allows rotation around the longitudinal axis of the bones. This joint thus plays a major role in the turning and rotational movements of the hand.

Joint capsule and strap lock

The common large joint capsule encloses all three partial joints and thus functionally combines them into the elbow joint. The joint capsule is attached to all three bones involved, i.e. the upper arm, radius and ulna. In the area between the ring ligament (explanation to follow) and the neck of the radial head, the joint capsule forms a bulge, the so-called recessus sacciformis.

This excess of capsule tissue serves as a reserve fold and is utilized when the forearm is completely rotated in one direction. The humeroulnar and humeroradial joints have strong ligament connections (collateral ligaments) that lie laterally against the joint capsule. These ligaments (ligamentum collaterale ulnare and ligamentum collaterale radiale) run in strong, fan-shaped paths, so that they support the joint laterally in any position: The ring ligament (Ligamentum anulare radii) originates at the ulna, moves around the head of the radius, and then returns to the ulna.

In this way it secures the proximal radioulnar joint.

• The Lig. collaterale ulnare extends from the bony prominence above the central humerus (Epicondylus medialis humeri) to the joint attachment of the upper arm at the ulna (Incisura trochlearis)
• The Lig. collaterale radiale originates from the bony protrusion above the lateral humerus (Epicondylus lateralis humeri) and then moves into the ring band.

Bursa sacs

Bursa sacs are fluid-filled, capsule-like, delimited cavities that lie outside the joint space and cushion strong mechanical stress. Bursae are either congenital or acquired (reactive bursae). Depending on the mechanical stress, each person develops bursae of different sizes in different places.

Due to this high individual variability, it is not possible to give an exact figure for the bursae of the elbow joint. The largest bursa in the elbow joint is called bursa subcutanea olecrani. It lies between the upper end of the ulna and the skin. High mechanical stress or an open wound can lead to bursitis.