Download Inferior (Distal) Radioulnar Joint Flexion and Extension

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Chapter 6
Table 6-1.
PHYSIOLOGIC MOTION
Physiological
Movement of the
Humeroradial Joint
Direction of
Slide of the
Radius on Capitulum
Flexion
Anterior
Extension
OF THE
ELBOW
Physiologic Motion
of the Radius
Direction of Slide of the
Distal Radius on the Ulna
When you pronate
The radial head moves posteriorly
(dorsal)
Posterior
When you supinate
The radial head moves anteriorly
(volar)
Physiological
Movement of
the Ulna
Direction of Slide
of the Ulna on
the Trochlea
Physiologic Motion
of the Radius
Direction of Slide of the
Distal Radius on the Ulna
Flexion
Distal/anterior
Varus angular with elbow
Lateral
Pronation
Anterior (volar)
Supination
Posterior (dorsal)
flexion
Extension
Proximal/posterior
Valgus angulation with
Medial
elbow in extension
at the elbow or in providing additional stability to the joint. The
resting position of the proximal radioulnar joint is 35 degrees of
supination and 70 degrees of elbow flexion. The position of greatest stability (close packed position) is in 5 degrees of supination.
The primary muscles involved at the radioulnar joint are the
supinator and the pronator quadratus.
Arthrokinetics
With pronation and supination of the forearm, the direction of
slide of the proximal radius on the ulna is opposite to the motion.
This is because the convex rim of the radial head articulates with
the concave radial notch on the ulna. With rotation of radius, the
convex rim moves opposite to the bone motion (Kisner & Colby,
1990) (see Table 6-1).
Inferior (Distal) Radioulnar Joint
This joint is at the distal end of the forearm near the wrist
where the ulnar notch of radius articulates with the head of the
ulna. This is an extremely stable joint due to the articular disk, the
interosseus between the radius and ulna and the pronator quadratus muscle.
Osteokinematics
Like the proximal radioulnar joint, the distal radioulnar joint is
a uniaxial pivot joint. In order to produce pronation and supination, the distal end of the radius must be free to move about the
ulna at its distal end as well as at the proximal portions (Jenkins,
1998). Rotation of the lower end of the radius around the head of
the ulna occurs at the distal radioulnar joint. The resting position
is in 10 degrees supination, and close packed position is in 5
degrees supination.
Arthrokinetics
The articulating surface of the radius slides in the same direction as the bone motion because the concave ulnar notch on the
distal radius articulates with the convex portion of the head of the
ulna (Kisner & Colby, 1990) (see Table 6-1).
MOVEMENTS
AT THE
ELBOW JOINT
Flexion and Extension
The flexion and extension movements that occur at the
humeroradial and humeroulnar joints are primarily gliding motions
until the last 5 to 10 degrees, when the surface joint motion
changes to rolling. The rolling in flexion occurs when the coronoid
process of the ulna comes into contact with the floor of the numeral coronoid fossa. During flexion, there is distal (inferior) glide of
the ulna in the trochlea. Supination and adduction of the ulna in
the trochlea and distal movement and pronation of the radius on
the humerus also occurs at the same time (Hamil & Knutzen,
1995). The capsule limits flexion more than extension and total
range of elbow flexion ranges from 135 to 146 degrees.