An important component of an orthopedic exam is assessment of muscle strength. Generally speaking, significant differences in strength between limbs are a sign of current or prior injury. Sophisticated strength measuring devices which measure forces generated isometrically, concentrically, or eccentrically exist but are both expensive and require a great deal of space.
Additionally, measurements are time consuming. It has long been a goal of NISMAT to develop a manual device for rapid measurement of strength, especially for the muscle groups which link the limbs to the torso. If you would like to read published abstracts regarding development and reliability of the MMT or Manual Muscle Tester, click here. The techniques that we describe for manual muscle testing are basically those described by Kendall and Kendall.
The device pictured here is called the Nicholas Manual Muscle Tester and is manufactured by Lafayette Instruments. The Nicholas MMT is a hand held device which quantifies the “breaking force” necessary to depress a limb held in a specific position by the patient. It is designed to be easily held in the palm of the hand and reports the force in kilograms.
NO TEST SHOULD BE PERFORMED IF THE SUBJECT IS FEELING ANY PAIN. The test is begun by first stabilizing the patient with the limb held in the desired position. The examiner instructs the patient to resist as hard as possible and then gradually applies a force to depress the limb.
The device records the peak force during the movement but care must be taken to stop applying force before the limb touches the side of the body, the floor or the table, depending on the motion being tested. Reliability of the measurements are high as long as the breaking forces being measured are 10% less than the maximum force that can be generated by the examiner.
The average of three trials in which a maximum effort is supplied following some practice trials gives the most reliable results. Allow at least 15 seconds between trials. Suggested positions for testing different muscles follow. Persons interested in purchasing an MMT should contact Lafayette Instruments (they manufactured the original, and still manufacture and sell this version of the device).
Hip Flexion
The examiner stands in front of the patient, seated on a bench that does not allow the feet to touch the ground. The patient flexes the hip approximately 8 inches off the bench and a downward force is applied by the examiner.
POINTS TO REMEMBER: position the curved plate just proximal to the top of the patella (not on the patella), do not impact the leg into the bench, have the subject maintain a torso position that is perpendicular to the table, have the patient grip the sides of the table for stabilization, examiner should use two hands if necessary.
CLINICAL PEARL: weakness in this motion is frequently associated with patella (knee cap) pathology.
Hip Abduction
The examiner stands behind the patient who is side lying on the bench. The contralateral leg is bent at the knee and the patient grasps the table with the ipsilateral hand to provide stabilization and to prevent rolling. The leg to be tested is raised about 12 inches off the table and the examiner applies a downward force.
POINTS TO REMEMBER: position the curved plate just proximal to the lateral malleolus, do not impact the leg into the table, have the subject maintain a torso position that is neutral with respect to trunk flexion, do not allow the subject to roll backwards to recruit the hip flexor muscles, be sure that the knee is locked in extension, DO NOT PERFORM THIS TEST ON SOMEONE WITH AN UNSTABLE KNEE.
CLINICAL PEARL: weakness in this motion is frequently associated with ankle sprains.
Hip Adduction
The position is similar to the test for abduction, except that the lower leg is being tested and the upper leg is bent and crossed in front the body so that the sole of the foot rests on the table. The lower leg is adducted about 6 inches off the table and a downward force is applied.
POINTS TO REMEMBER: position the curved plate just proximal to the medial malleolus, do not impact the leg into the table, be sure that the knee is locked in extension, DO NOT PERFORM THIS TEST ON SOMEONE WITH AN UNSTABLE KNEE.
CLINICAL PEARL: weakness in this motion is associated with most knee pathologies. You can document atrophy of this muscle group easily by having the patient do a full squat and comparing the muscle mass on the inside of the thigh to the other thigh.
Shoulder Abduction
The patient is seated either on a chair with a straight firm back or on a table. The arm is abducted to approximately 90 deg. with the palm facing down. The subjects contralateral hand grabs the side of the table to help stabilize. A downward force is administered by the examiner.
POINTS TO REMEMBER: position the curved plate just proximal to the styloid process on the dorsum of the wrist, do not impact the arm into the patient’s side, be sure the elbow remains locked.
CLINICAL PEARL: weakness is apparent in this motion in people with rotator cuff tears and impingement.