BIOMECHANICS OF ELBOW COMPLEX LECTURE-1 BIOMECHANICS OF ELBOW COMPLEX Prepared by: Dr. Ishaq Ahmed MSPT(KMU), BSPT(UHS), t-DPT(KMU)

Arthokinametics

Elbow Joint Characteristics and Arthokinametics The elbow is a compound joint with a lax joint capsule, supported by two major ligaments—the medial (ulnar) and lateral (radial) collateral—which provide medial and lateral stability, respectively.

Humeroulnar Articulation The humeroulnar (HU) articulation is a modified hinge joint. The medially placed hourglass shaped trochlea at the distal end of the humerus is convex. It faces anteriorly and downward 45 from the shaft of the humerus The concave trochlear fossa, on the proximal ulna, faces upward and anteriorly 45 from the ulna The primary motion at this articulation is flexion and extension

Arthokinametics During flexion/extension the concave fossa slides in the same direction in which the ulna moves, so with elbow flexion the fossa slides around the trochlea in an anterior and distal direction With elbow extension, the fossa slides in a posterior and proximal direction

Arthrokinematics There is also slight medial and lateral sliding of the ulna, allowing for full elbow range of motion (ROM); it results in a valgus angulation of the joint with elbow extension and a varus angulation with elbow flexion

Carrying angle

Humeroradial Articulation The humeroradial (HR) articulation is a hinge-pivot joint. The laterally placed, spherical capitulum at the distal end of the humerus is convex. The concave bony partner, the head of the radius, is at the proximal end of the radius. Flexion/extension and pronation/supination occur at this articulation.

Arthrokinematics As the elbow flexes and extends, the concave radial head slides in the same direction as the bone motion so with elbow flexion the concave head slides anteriorly and with elbow extension it slides posteriorly With pronation and supination of the forearm, the radial head spins on the capitulum

Proximal (Superior) Radioulnar Articulation The proximal radioulnar (RU) articulation is within the capsule of the elbow joint but is a distinct articulation The convex rim of the radial head articulates with the concave radial notch on the ulna and the annular ligament. This ligament encircles the rim of the radial head and stabilizes it against the ulna. The primary motion is pronation/supination.

Arthrokinematics As the forearm rotates into pronation and supination, the convex rim of the radial head slides opposite the bone motion, so with pronation the head slides posteriorly (dorsally) on the radial notch and with supination it slides anteriorly (volarly). It also slides in the annular ligament and the proximal surface spins on the capitulum.

Distal (Inferior) Radioulnar Articulation The distal RU joint is an anatomically separate joint at the distal end of the radius and ulna. The concave ulnar notch on the distal radius articulates with the convex notch on the head of the ulna. It, along with the proximal RU joint, participates primarily in pronation/supination.

Arthrokinematics As the forearm rotates, the concave radius slides in the same direction as the physiological motion. It slides anterior (volar) with pronation and posterior (dorsal) with supination.

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