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Functions of Humeroulnar and humeroradial joints - Coggle Diagram
Functions of Humeroulnar and
humeroradial joints
Axis of Motion
Not a fixed axis
Because the elbow is not a pure hinge joint
The axis of motion for flexion and extension
is
centered in the middle of trochlea on a line that
intersects the longitudinal axis of the humerus
Variations in the axes appear to be greater in the
frontal plane than in the horizontal plane
Ulna is guided progressively medially from extension to flexion
In extension forearm moves laterally until it reaches
a position slightly lateral to the axis of humerus
Long axes of humerus and forearm
In anatomical position
Long axis of humerus and the long axis of forearm form an
acute angle medially at the elbow joint
Carrying angle (around 15 degrees)
Due to the configuration of the articular surfaces of
humeroulnar joint
Cubital Valgus
Normal valgus angulation
Lateral deviation of ulna in relation to humerus
Cubital Varus
Abnormal angulation
Medial deviation of ulnar in relation to humerus
Variations in carrying angle
Shorter individuals have a greater angle
Younger individuals have a lesser angle
Females have a greater angle
Mobility
ROM is dependent on a number of factors
1.Type of Motion
Active
from 135 -145 degrees of flexion
Passive
from 150 - 160 degrees
2.Position of the forearm
(relative supination or pronation)
Pronated or neutral position of foreram, ROM is less when compared to supinated forearm
3.Body mass index
High BMI has limited range of motion at elbow
5.position of the shoulder
Dependent on 2 joint muscles that cross both shoulder and elbow
Biceps brachii and triceps brachii
Limits ROM at elbow joint if full ROM is attempted at both joints simultaneously
4.Swelling and pain may also reduce ROM
Stability related ROM
Dependent on the
configuration of joint surfaces,
ligaments and
the joint capsule
Close-packed position of humeroulnar joint is the
full extension
Olecranon process in the olecranon fossa
Provides valgus and varus stability
Bony components, medial collateral ligament, anterior joint capsule
will resist valgus stress equally
Flexor carpi ulnaris and the pronator teres contribute to the
medial support of elbow
Bony components can only provide half resistance to limit varus stress,
while the other half is provided by the
lateral collateral complex and the
joint capsule
Resistance to joint distraction is provided by the
soft tissue structures
Anterior component of the joint capsule
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At the extreme of Flexion
Approximation of coronoid process with the coronoid fossa
Approximation of the rim of the radial head in the radial fossa
At 90 degrees of flexion
Anterior part of the medial collateral ligament provides resistance to both distraction
and valgus stress
If overstretched, can become instable
Majority of resistance to varus stress provided by the bony components
Anterior joint capsules contribution is only slightly when flexed
During forceful motions,
co-contraction of the flexors and extensors of the
elbow, wrist and hand
provide stability for the elbow joint