BIOMECHANICS OF ELBOW
COMPLEX
LECTURE-1

Introduction
“ The elbow complex includes the elbow joint
(humeroulnar and humeroradial joints) and
the proximal and distal radioulnar joints.”

Introduction
 The elbow joint is considered to be a compound
joint that functions as a modified or loose hinge
joint made up of humrus, ulna and the radius
bones
 Function: properly place hand in space by
shortening and lengthening the upper limb
 Most upper extremity movements involve the
elbow and radioulnar joints
 One degree of freedom is possible at the elbow,
permitting the motions of flexion and extension,
which occur in the Sagittal plane around a coronal
axis

Introduction
 A slight bit of axial rotation and side-to-side
motion of the ulna occurs during flexion and
extension, and that is why the elbow is considered
to be a modified or loose hinge joint rather than a
pure hinge joint

Introduction
 The proximal and distal radioulnar joints
are linked and function as one joint
 The two joints acting together produce
rotation of the forearm and have 1 degree of
freedom of motion.

Bones and Landmarks

Bones and Landmarks

Humeroulnar Joint
 The hinge joint at the elbow is the
humeroulnar joint, where the ovular
trochlea of the humerus articulates with the
reciprocally shaped trochlear fossa of the
ulna . Flexion and extension are the primary
movements, although in some individuals, a
small amount of hyperextension is allowed.
The joint is most stable in the close-packed
position of extension

Humeroradial Joint
The humeroradial joint is immediately lateral to the
humeroulnar joint and is formed between the
spherical capitellum of the humerus and the proximal
end of the radius . Although the humeroradial
articulation is classified as a gliding joint, the
immediately adjacent humeroulnar joint restricts
motion to the sagittal plane.
In the close-packed position, the elbow is flexed at
90° and the forearm is supinated about 5°

Proximal Radioulnar Joint
The annular ligament binds the head of the
radius to the radial notch of the ulna, forming
the proximal radioulnar joint. This is a pivot
joint, with forearm pronation and supination
occurring as the radius rolls medially and
laterally over the ulna . The close-packed
position is at 5° of forearm supination

Carrying Angle
 The angle between the longitudinal axes of
the humerus and the ulna when the arm is in
anatomical position is referred to as the
carrying angle. The size of the carrying
angle ranges from 10° to 15° in adults and
tends to be larger in females than in males.
The carrying angle changes with skeletal
growth and is always greater on the side of
the dominant hand.

Ligaments
Ulnar collateral ligament
 medial side of the elbow
 extends from medial epicondyle of humerus
to proximal portion of ulna
 function is to prevent excessive abduction
of elbow joint

Ligaments
Radial collateral ligament
 lateral side of the elbow
 extends from lateral epicondyle of humerus
to head of radius
 function is to prevent excessive adduction
of elbow joint

Ligaments

Ligaments
 Ulnar collateral ligament is critical in
providing medial support to prevent the
elbow from abducting when stressed in
physical activity
 Many contact sports and throwing activities
place stress on the medial aspect of the
joint, resulting in injury.
 Radial collateral ligament provides lateral
stability and is rarely injured

Medial Ligament stress

Ligaments
Annular ligament
 provides stability for
radial head during
pronation and
supination
 commonly injured in
children when arm
pulled forcefully

Interosseous Membrane
 The joint between
shafts of radius & ulna
held tightly together
between proximal and
distal articulations by
an interosseous
membrane

MOVEMENTS AT THE
ELBOW
 Flexion and Extension
Elbow flexors
Brachialis strongest flexor (effective in both
supination / pronation )
Biceps brachii (effective in supination )
Brachioradialis Weak assistance from Pronator teres
( effective in neutral )
Elbow extensor
Triceps brachii (70 to 90 % extension )
Anconeus provides assistance (15%)

 The major pronator muscle is the pronator
quadratus.
 The major supinator muscle is the supinator
 When the elbow is in flexion, tension in the
supinator lessens, and the biceps assists
with supination. When the elbow is flexed
to 90° or less, the biceps is positioned to
serve as a supinator.

COMMON INJURIES OF THE
ELBOW
 Forced hyperextension of the elbow can
cause posterior displacement of the
coronoid process of the ulna with respect to
the trochlea of the humerus. Such
displacement stretches the ulnar collateral
ligament, which may rupture (sprain)
anteriorly.

 Elbow dislocations in young children age
1–3 are sometimes referred to as
“nursemaid’s elbow” or “pulled elbow.”
Adults should avoid lifting or swinging
young children by the hands, wrists, or
forearms, as this type of injury can result

Lateral epicondylitis
 involves infl ammation or microdamage to
the tissues on the lateral side of the distal
humerus, including the tendinous
attachment of the extensor carpi radialis
brevis and possibly that of the extensor
digitorum

Medial epicondylitis,
 which has been called Little Leaguer’s
elbow, is the same type of injury to the
tissues on the medial aspect of the distal
humerus.