Elbow MRI Anatomy Overview

Overview

This lecture reviews the anatomy of the elbow joint as seen on MRI, covering bones, tendons, muscles, ligaments, and nerves, to help identify normal structures and distinguish pathology.

Bones of the Elbow Joint

• The elbow joint consists of the humerus (proximal), radius (lateral), and ulna (medial).
• The distal humerus includes the lateral and medial epicondyles, trochlea, and capitellum.
• The radius is divided into head, neck, shaft, and radial tuberosity (biceps tendon attachment).
• The ulna features the olecranon (posterior), trochlear notch, coronoid process (anterior), shaft, and ulnar tuberosity (brachialis insertion).

Major Muscles and Tendons

• Biceps brachii (two heads) forms a tendon attaching to radial tuberosity; major elbow flexor.
• Brachialis originates from humerus and inserts on ulnar tuberosity; assists in elbow flexion.
• Triceps brachii (three heads) inserts on the olecranon; main elbow extensor.
• Common extensor tendon (lateral) gives rise to extensor carpi ulnaris, extensor digitorum, extensor digiti minimi.
• Common flexor tendon (medial) gives rise to pronator teres, flexor carpi ulnaris/radialis, flexor digitorum superficialis, palmaris longus.

Ligaments of the Elbow

• Ulnar collateral ligament (UCL) has anterior, posterior, and transverse bundles; anterior is most important for stability and injury (e.g. throwers).
• Radial collateral ligament (RCL) connects lateral epicondyle to annular ligament.
• Annular ligament encircles the radial head, allowing pivot motion.
• Lateral ulnar collateral ligament (LUCL) and posterior ligament contribute to stability.

Nerves Crossing the Elbow

• Ulnar nerve passes posterior to the medial epicondyle ("funny bone"), enters forearm via flexor carpi ulnaris.
• Radial nerve wraps posteriorly around humerus, divides into superficial and deep branches near elbow, deep branch passes between brachioradialis and supinator.
• Median nerve passes anteriorly through cubital fossa.

Common Anatomic Variants and MRI Findings

• Trochlear ridge: normal cartilage gap seen laterally and medially; not a foreign body or cartilage defect.
• Posterior capitellum lacks cartilage naturally on MRI; normal variant.

Key Terms & Definitions

• Trochlear notch — concave ulna surface articulating with humeral trochlea.
• Olecranon — proximal bony prominence of ulna, triceps insertion.
• Epicondyle — bony humerus projection (medial/lateral), tendon/ligament attachment.
• Radial tuberosity — bony prominence on radius, biceps tendon insertion.
• Annular ligament — ligament encircling radial head, stabilizing proximal radioulnar joint.
• Ulnar collateral ligament (UCL) — medial elbow stabilizer; prone to injury in throwers.
• Cubital fossa — anterior elbow crease; median nerve location.

Action Items / Next Steps

• Review elbow radiograph tutorial if basic anatomy is unclear.
• Study normal elbow MRI anatomy to recognize pathology.
• Prepare for next week's lecture on foot and ankle imaging.