Origin:
Long Head:
Scapula (blends
above with the capsule of the glenohumeral joint
Lateral Head:
Humerus (shaft: oblique ridge, posterior surface)
Lateral intermuscular septum
Medial Head:
Humerus (shaft:
entire length of posterior surface)
Medial and lateral intermuscular septa
Humerus (medial
border)
Insertion: All heads
have a common tendon to:
Ulna
(olecranon process, upper surface); blends with antebrachial fascia capsule of
elbow joint
Innervation: Cervical root(s): C6–C8
Nerve:
radial (ventral rami)
Grading of muscle strength:
Grade
|
Strength
|
Description
|
5*
|
Normal
|
Normal strength
|
4*
|
Good
|
Movement against
external resistance but less than normal
|
3
|
Fair
|
Movement against
gravity but not against added resistance
|
2
|
Poor
|
Movement at the joint
with gravity eliminated
|
1
|
Trace
|
Trace of contraction
but no movement at the joint
|
0
|
Zero
|
No contraction or
muscle movement
|
*The distinction between
Grades 4 and 5 is based on comparison with the normal hand and, barring that,
extensive experience in testing the hand.
|
Position of patient's hand and upper
extremity
- The patient lies prone on a table and starts the
test with the arm in 90° abduction and the forearm is flexed and hanging
vertically over the table’s side. Some suggest that for Grades 0 and 1, the
patient be seated with the arm abducted to 90° and the shoulder in neutral
rotation and the elbow flexed to about 45°. The entire limb is horizontal to
the floor.
Examiner’s Actions
- For the prone patient, the examiner provides
support just above the elbow, while using the other hand to apply downward
resistance on the dorsal surface of the forearm. Some suggest that the examiner
support the limb at the elbow, and that for Grades 0 and 1, the examiner also
palpates the limb under the forearm and the triceps on the posterior surface of
the arm just proximal to the olecranon process.
Instructions for the patient
- “Straighten your elbow. Hold it. Don’t let me
bend it.” Some suggest “Try to straighten your elbow” for Grades 0–2.