Muscle Test and Tendon Exam: Extensor Carpi Ulnaris (ECU)

Exams and Signs

Origin:	Humerus (lateral epicondyle via common extensor tendon) Ulna (posterior border by an aponeurosis)
Insertion:	5th metacarpal bone (tubercle on medial side of base)
Innervation:	Cervical root(s): C7 and C8 Nerve: Radial nerve (posterior interosseous branch)

Grading of muscle strength:

Grade	Strength	Description
5*	Normal	Completes full range of motion against maximal finger resistance
4*	Good	Tolerates moderate resistance
3	Fair	Completes full range of motion with no resistance
2	Poor	Completes partial range of motion
1	Trace	Slight contractile activity
0	Zero	No contractile activity
*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

Sitting with elbow flexed, the forearm is fully pronated, and both are supported on a table. Some suggest that for Grade 2, the forearm is supported on a table in neutral position, and for Grades 0 and 1, the forearm is supported on a table with the hand fully pronated.

Examiner’s Actions

Sitting or standing at a diagonal in front of patient, support the patient’s forearm and place the hand used for resistance over the dorsal (extensor) surface of metacarpals. Some suggest that for Grade 2, the examiner supports the patient’s wrists for testing, and for Grades 0 and 1, the examiner supports the patient’s wrist in extension. For these Grades, the examiner palpates the tendon on the dorsal surface proximal to the fifth metacarpal and just distal to the ulnar styloid process.

Instructions for the patient

“Bring your wrist up. Hold it. Don’t let me push it down.” Some suggest “bend your wrist back” for Grade 2, and “Try to bring your wrist back” for Grades 0 and 1.

Presentation Photos and Related Diagrams

ECU Muscle Testing
ECU anatomy illustration
This illustration represents the anatomy of the muscle and tendon origin and insertion. Should an individual sustain a laceration as depicted, the observer can assume that the underlying tendon may be at risk for complete transection. A proper examination is needed to determine the integrity of the tendon.

Definition of Positive Result

In muscle testing, a normal result is a positive one. During a normal muscle test, the examiner should observe a normal muscle contraction that can move the joint or tendon against full resistance.

Definition of Negative Result

In muscle testing, an abnormal result is a negative one. During an abnormal muscle test, the examiner should observe an abnormal muscle contraction that can move the joint or tendon. In a complete denervation injury, such as a complete nerve laceration, there will be no evidence of any muscle function and the muscle testing grade will be

Comments and Pearls

The ECU is considerably weaker than the extensor carpi longus or extensor carpi brevis.
A patient with complete quadriplegia at C5–C6 will have only radial wrist extensors remaining; radial deviation during extension is therefore the prevailing extensor motion at the wrist.

Diagnoses Associated with Exams and Signs

References

Hislop JH, Avers D, Brown M. Daniels and Worthingham's Muscle Testing, Techniques of Manual Examination and Performance Testing. 9th ed. St. Louis, Missouri: Elsevier Saunders, 2014, pp. 138–202.
Kendall FP, McCreary EK, Provance PG. Muscles Testing and Function. 4th ed. Baltimore, MD: Williams & Wilkins, 1993, pp. 235–298.