Elbow Joint: Anatomy and Movement

• The elbow joint is a uniaxial, synovial hinge joint.

Articulation

• Superiorly, the elbow joint articulates with the humerus, specifically the trochlea and capitulum.
• Inferiorly, it articulates with the head of the radius and the trochlear notch of the ulna.

Capsule

• The elbow joint capsule encloses the three articulating bones.
• It is lax anteriorly and posteriorly to allow for full flexion and extension.
• The capsule is reinforced on each side by collateral ligaments.

Ligaments

• The elbow's lateral (radial collateral) ligament consists of one fan-shaped band.
• The medial (ulnar collateral) ligament has three bands: an anterior strong cord-like band, a posterior weaker fan-like band, and a transverse band.

Movement

• Flexion is enabled by the brachialis, biceps brachii, and brachioradialis (in mid-prone position)
• Flexion is also facilitated by the superficial flexors of the forearm.
• Extension is enabled by the triceps brachii and anconeus.
• Superficial extensors of the forearm also aid extension, excluding the brachioradialis.

Carrying Angle

• With the elbow fully extended, the ulna makes an angle of approximately 170° with the long axis of the humerus.
• The angle is more acute (by 10°) in females than in males.

Stability

• The elbow joint is considered a stable joint due to the shape of its articulating bones and the presence of strong medial and lateral ligaments.

Clinical Anatomy - Dislocation

• Elbow dislocations can result from hyperextension or a blow driving the ulna posteriorly.
• Posterior dislocation of the elbow joint can occur when children fall on their hands with their elbows flexed.

Clinical Anatomy - Avulsion of Medial Epicondyle

• Avulsion of the medial epicondyle is common in children and is typically caused by a fall on the extended elbow.
• Traction on the ulnar collateral ligament pulls the medial epicondyle distally.
• The epiphysis for the medial epicondyle may not fuse with the distal end of the humerus until around age 20.
• This injury can lead to ulnar nerve injury.

Clinical Anatomy - Fracture of Olecranon

• Fracture of the olecranon is common due to being subcutaneous and protrusive.
• A fall on the elbow combined with sudden powerful contraction of the triceps brachii often causes the fracture.
• The fractured olecranon is pulled away due to active and tonic contraction of the triceps.

Clinical Anatomy - Epicondylitis

• Lateral epicondylitis is known as tennis elbow.
• Medial epicondylitis is called golfer's elbow.