Human Anatomy: Elbow

Elbow Joints

3 joints proximal-radioulnar joint: small point of contact between concave radial notch of ulna and convex radial head (of radius) radiohumeral/humeroradial joint: between shallow radial head and ball-shaped capitellum. Not very congruent humeroulnar joint: medial part of joint contains trochlea within trochlear notch, very congruent. The coronoid and olecranon processes surround the joint. Joint itself is angled "carrying angle" so when the elbow is flexed, it doesn't move fully in the sagittal plane.

Osteology of Humerus

Distal End anterior: medial side: Coronoid fossa (depression) for the coronoid process of ulna to fit in during flexion lateral side: radial fossa for the radial head (of radius) during flexion Below fossa are articular surfaces: capitellum (lateral side, rounded, ball shaped) and trochlea (medial side, hourglass shape) Condyles and associated epicondyles (on the ends of the condyles) are points for muscle attachments Has an anterior inclination on distal end to allow for full ROM for from extension to flexion. From a posterior view of the distal end: trochlea is the only articular surface that is visible. Olecranon fossa where olecranon process of ulna fits during extension Medial and lateral supracondylar ridges -> points of muscle attachment

Cubital Fossa

Inverted triangular space on the inside of the elbow. Where blood is drawn. Superior bound: medial/lateral epicondyle Medial bound: pronator teres muscle Lateral bound: brachioradialis muscle Floor bound: brachialis and supinator muscle

Elbow Joint Capsule

Joint capsule encloses all three elbow joints. During flexion/extension some aspects of the capsule are on slack and some are on tension. Capsule ligaments reinforce medially and laterally Humerus, radius, and ulna must stay together to keep joint capsule intact. Fibrous part of the anterior join capsule has the brachialis muscle running over it. Only joint in the body where there's only muscle belly running over the capsule, making it difficult to return to full ROM (esp extension) after immobilization.

Collateral Ligaments of Elbow Joint (Lateral)

Lateral Collateral Ligament (also known as radial collateral ligament or LCL Complex) provides lateral stability, but is not as important as the MCL. Originates at lateral epicondyle and attaches to annular ligament and ulna. The part that attaches to the ulna is called the lateral ulnar collateral ligament. Has no direct attachment to radius (only attaches to annular ligament which wraps around radial head and ulna) to allow for pronation/supination. LCL is attachment site for forearm extensor muscles and those that attach on the lateral epicondyle. Muscles that attach here run posterior on forearm and are innervated by the radial nerve.

Collateral Ligaments of Elbow Joint (Medial)

Medial Collateral Ligament (also known as ulnar collateral ligament): triangular in structure. Has anterior, posterior, and transverse bands. Transverse band runs from olecranon process to coronoid process; only stretched if medial side of humerus is pushed towards it -> acts to keep medial part of humerus in place. Posterior band runs from medial epicondyle to olecranon process. Anterior band runs from medial epicondyle to coronoid process. Ligaments are also an attachment site for forearm muscles on medial side of forearm. Medial forearm muscles (innervated by median nerve or branches from ulnar nerve) run from medial epicondyle to anterior side of hand/wrist

pronation/supination of forearm

Occur at the proximal and distal radioulnar joint ONLY In supination, radial head sits laterally to ulna. As the forearm moves into pronation, the radius spins at the proximal radioulnar joint and roll/slides at the distal radioulnar joint. Concave surface of distal races moves on convex surface of ulna.

Osteology of Ulna

Proximal End of Ulna Trochlear notch: trochlea of humerus sits in trochlear notch. Contains a ridge in the middle, which aligns with the groove in humeral trochlea to make the joint more congruent. Olecranon process: creates the tip of the elbow. Joins with the coronoid process. Coronoid process, radial notch, and trochlear notch are covered with articular cartilage. Medial proximal side of ulna doesn't have an articular surface with the radius. Lateral proximal side has a radial notch for the head of the radius.

Osteology of Radius

Proximal end of radius Articular cartilage covers the radial head and edges Neck of radius is more narrow than the radial head Anterior side: radial tuberosity where biceps brachii attaches. Medial surface: "sharp" appearance, attachment site for interosseous membrane Distal end: flares laterally and projects posteriorly to create a bi-concave articular surface

Interosseous Membrane

flexible membrane connecting radius and ulna that provides stability between shafts of ulna and radius. Fibers run in an oblique direction

Proximal Radioulnar Joint

head of radius (convex) articulates with radial notch of ulna (concave) Annular ligament wraps around head of radius to provide support to joint

Distal Radioulnar Joint

head of ulna articulates with ulnar notch of radius