Comparative Assessment of Knee Strength Using Hand-Held Myometry and Isometric Dynamometry in Patients with Inflammatory Myopathy

Inflammatory myopathy is a group of disorders with progressive muscle weakness being the major symptom. Quantitative assessment of muscle function is important when evaluating the response of these conditions to treatment and various methods, including manual muscle testing, myometry and isokinetic dynamometry, have been used for the assessment of muscle strength. The aims of this study were to compare, in patients with inflammatory myopathy, the maximum isometric quadriceps and hamstrings torques using a hand-held myometer and a dynamometer (Kin-Com), and to compare make and break tests using myometry. The results showed that in stronger quadriceps the myometer tests underestimated maximum torque as measured with the dynamometer, and that in weaker quadriceps there was no difference in torque with the different methods. There was no difference in hamstrings make torques for the two instruments. The break myometer torques were greater than the make torques for both muscle groups. These findings indicate that when using myometry, break tests measure maximum torque more accurately than make tests, and that isometric dynamometry is preferable to myometry when testing maximum strength of large muscles of near normal strength.