MEDICAL UNIVERSITY OF SOUTH CAROLINA
COLLEGE OF HEALTH PROFESSIONS
REHABILITATION SCIENCES DEPARTMENT
Functional Anatomy of the Elbow
The elbow is sometimes termed a "power" joint, and is
important in lifting. The elbow is operated largely by powerful
muscles of the arm, and is created by the humeroulnar joint, where
the articulation actually occurs. The humeroradial joint which
is created by the surrounding articular capsule, is not an actual
functional joint, but represents a bony relationship which is
included in the elbow complex.
A. Classification of the joints of the elbow complex:
- Humeroulnar joint - the joint is a hinge joint, and extension,
flexion are the only motions occurring here.
- The humeroradial joint is unclassified.
B. Direction of excursion of the humeroulnar joint and elbow ligaments
and muscles:
- In the normal subject, full extension should be achieved to
180o; whereas 0° to
145° flexion is considered normal.
The forearm, however, does not normally hang along the line of
the humerus, but rather achieves a laterally produced angle of
about 170o (males) to 165°
(females). This is called the "carrying angle" and is
produced by the lateral shaft of the trochlea of the humerus as
it articulates with the trochanteric notch of the ulna.
- The normal subject should be able to achieve up to approximately
145o flexion of the forearm upon the humerus.
- Elbow ligaments:
a. Articular capsule - This capsule is loose and surrounds the
elbow complex. Thinner posteriorly, the capsule allows for movement
of the elbow, while offering good protection for the integrity
of the joint. Most dislocations of the elbow, however, occur posteriorly,
due to the relatively thin aspect of the posterior capsule.
b. Anconeus - The anconeus is a small muscle attaching to the
articular capsule of the elbow and ulna. Its function is to pull
the capsule out of the elbow joint upon active extension of the
elbow. The anconeus also assists the triceps brachii in extending
the elbow.
c. Collateral ligaments: The collateral ligaments support the
elbow complex, and may be observed running along either side.
The collateral ligaments strengthen the articular capsule medially
and laterally. They are termed the ulnar (medial) collateral ligament
of the elbow and the radial (lateral) collateral ligament of the
elbow.
- The ulnar collateral ligament (UCL) is a broad, triangular
shaped ligament. The band consists of an anterior, posterior,
and intermediate portions. The apex of the UCL is attached to
the medial epicondyle of the humerus; the ligament thendivides
into anterior and posterior portions, with the anterior portion
coursing to attach distally to the coronoid process, and the posterior
portion coursing to attach distally to the olecranon process.
The intermediate portion of the ulnar collateral ligament has
fibers which run between and connect the anterior and posterior
portions.
- The radial collateral ligament is a cord-like ligament and
may be observed coursing the elbow laterally. Arising from the
lateral epicondyle, it courses distally in a single division to
attach to the annular ligament (the annular ligament is a circular
ligamentous structure which encircles the head of the radius and
attaches to either side of the radial notch of the ulnar notch,
thus forming the proximal radioulnar joint.
- Muscles acting on the elbow include the large muscles of the
arm, i.e. for flexion, the biceps brachii and brachialis, and
for extension the triceps brachii. A muscle of the posterior compartment
of the forearm, the brachioradialis also functions as an elbow
flexor.
Innervation, Blood Supply and Tendons of the Wrist and Hand-Muscles of the Hand -Movements of the Hand - Surface Anatomy of the Hand -Skeleton of the Hand - Wrist and Hand Index
Last modified: 9:18 PM on 10/19/96
© 1996 Reigart, Murphy