MSK I Elbow and Forearm - Vocabulary Flashcards

Vocabulary flashcards covering the key elbow and forearm anatomy, joints, ligaments, biomechanics, and resting/packed positions from the notes.

Humeroulnar joint

The true hinge joint between the humerus (trochlea) and the ulna (trochlear notch); primary elbow joint for flexion-extension; normally valgus 10–15° with ROM ≈140°; contributes to stability of the elbow.

Humeroradial joint (Radiocapitellar joint)

Articulation between the radial head and the capitellum; stabilizer against valgus forces; contact changes with flexion; about 57% of load can travel through this joint.

Proximal radioulnar joint (PRUJ)

Site of forearm rotation near the elbow; allows ~240° of rotation for pronation/supination; works with the DRUJ; stabilized by the interosseous membrane.

Distal radioulnar joint (DRUJ)

Distal counterpart to the PRUJ allowing pronation-supination at the wrist; functionally interdependent with the PRUJ and interosseous membrane.

Interosseous membrane

Fibrous partition between the radius and ulna; distributes load and provides additional stability for PRUJ/DRUJ during rotation.

Annular ligament

Ligament surrounding the radial head, attaching to the ulna; acts as a sling to keep the radial head in place (~80% of radial head covered); stabilizes during rotation.

Medial Collateral Ligament (UCL)

Elbow ligament on the medial side resisting valgus stress; comprises anterior, posterior, and transverse parts; forms the floor of the cubital tunnel.

Lateral Collateral Ligament (RCL)

Radial collateral ligament on the lateral elbow resisting varus stress; includes anterior, posterior, and transverse components.

Carrying angle

Natural valgus angle of the elbow (about 10–15°); influences distribution of stress and susceptibility to valgus injury.

Trochlea

Medial spool-shaped part of the distal humerus that articulates with the ulna’s trochlear notch; central to the hinge mechanism.

Trochlear notch

Concave anterior portion of the ulna that articulates with the trochlea; key component of the hinge joint.

Coronoid fossa

Fossa on the anterior distal humerus that accommodates the coronoid process of the ulna during flexion.

Olecranon fossa

Posterior distal humerus fossa that accommodates the olecranon of the ulna during full extension.

Capitulum

Rounded lateral distal humeral surface that articulates with the head of the radius.

Radial head

Proximal end of the radius that articulates with the capitellum; contact increases with flexion; stabilizes against valgus stresses.

Radial notch of the ulna

Ulna notch that articulates with the radial head to form the PRUJ.

Joint capsule

A single capsule enclosing the elbow complex; allows for variable laxity in open packed positions and becomes taut in closed packed positions.

Open packed position (elbow joint)

Elbow position with greatest capsular/ligament laxity; commonly cited as around 80° of flexion in the elbow capsule.

Closed packed position (elbow joint)

Position with maximal ligamentous tension and joint stability: 0° extension for the trochlear joint and ~90° flexion for the radiocapitellar joint.

Normal elbow ROM

Typical flexion-extension range about 140°; used as a reference for functional movement.

Load distribution between joints

Axial loads transmitted through the elbow are distributed approximately 43% via the humeroulnar joint and 57% via the humeroradial joint.

Forearm rotation (pronation/supination)

Rotational movements of the forearm around the PRUJ/DRUJ, enabling palm orientation changes.

Adaptive shortening and contracture

Prolonged shortening of periarticular structures leading to stiffness and eventual joint contracture; the “unforgiving joint.”

Annular ligament coverage

Annular ligament surrounds about 80% of the radial head, aiding stability of the PRUJ during rotation.

Valgus stress and MCL injury risk

The elbow’s natural carrying angle predisposes to valgus stress; excessive valgus loading increases risk to the MCL and related structures.

Best resting position for the elbow

Open packed position with joints least constrained; in this context, elbow flexion around 80° is noted as a lax position for rest.

Elbow joints count (anatomical quiz note)

Elbow involves two main joints (humeroulnar and humeroradial) and the proximal radioulnar joint (forearm) functioning as part of the elbow complex.