1. Bones Involved:
The elbow joint is a hinge-like joint primarily composed of three bones:
- Humerus: The lower end of the humerus, known as the distal humerus, forms the upper part of the elbow joint.
- Ulna: The ulna, one of the two forearm bones, forms the main joint with the humerus.
- Radius: The radius, the other forearm bone, moves along the ulna during elbow movements.
2. Joint Configuration:
- The distal humerus has two condyles (rounded articular surfaces): the trochlea medially and the capitulum laterally.
- The ulna has a concave structure called the trochlear notch that articulates with the trochlea of the humerus.
- The radius has a rounded head that articulates with the capitulum of the humerus.
3. Ligaments:
Several ligaments provide stability and support to the elbow joint:
- Medial Collateral Ligament (MCL): Located on the inner side of the elbow, the MCL prevents excessive outward bending.
- Lateral Collateral Ligament (LCL): Situated on the outer side of the elbow, the LCL limits excessive inward bending.
- Annular Ligament: Surrounds the head of the radius, holding it in place against the capitulum of the humerus.
4. Muscles and Tendons:
- Biceps brachii: This muscle is responsible for bending (flexing) the elbow.
- Triceps brachii: The triceps extends (straightens) the elbow.
- Brachioradialis: Helps flex the elbow and supports forearm rotation.
- Supinator: Involved in forearm rotation, aiding in turning the palm upward.
- Pronator teres and pronator quadratus: Work together to turn the palm downward.
5. Joint Movements:
- Flexion: Bending the elbow joint, decreasing the angle between the upper and lower arm.
- Extension: Straightening the elbow joint, increasing the angle between the upper and lower arm.
- Pronation: Turning the palm downward so that it faces the ground.
- Supination: Turning the palm upward so that it faces the sky.
The elbow joint's coordinated movement is essential for performing daily tasks, such as lifting, reaching, grasping objects, and fine motor activities like writing. Proper functioning of the joint depends on the harmonious interplay of bones, ligaments, muscles, and tendons, which work together to provide stability and mobility to the elbow.