Küünarliigese

The küünarliigese, or elbow joint in English, is a complex hinge joint formed by three bones: the humerus, the ulna, and the radius. Its primary function is to allow for flexion and extension of the forearm, bringing the hand closer to or further from the shoulder. It also facilitates pronation and supination, the movements that turn the palm downwards and upwards, respectively.

The humerus, the bone of the upper arm, articulates with the ulna at the trochlear notch, forming the main hinge of the joint. This articulation is responsible for the bending and straightening motion. The distal end of the humerus also has a rounded capitulum which articulates with the head of the radius. This radial-humeral joint allows for the rotation of the radius during pronation and supination.

The ulna, the larger of the two forearm bones, is also involved in the hinge movement through its olecranon process, which forms the point of the elbow. The radius, the smaller forearm bone, runs parallel to the ulna. Its head is a disc-shaped structure that fits into a shallow depression on the capitulum of the humerus and also articulates with a notch on the ulna, enabling the rotational movements.

Ligaments play a crucial role in stabilizing the küünarliigese. The ulnar collateral ligament on the medial side and the radial collateral ligament on the lateral side provide stability against forces that could dislocate the joint. The annular ligament encircles the head of the radius, holding it in place against the ulna and allowing it to rotate freely. The joint is further enclosed by a capsule filled with synovial fluid, which lubricates the surfaces and nourishes the cartilage. Injuries to the küünarliigese can range from sprains and fractures to dislocations, affecting the intricate mechanics of arm movement.