Reliability of hand-held dynamometry in assessment of knee extensor strength after hip fracture

Objectives: To examine the reliability of hand-held dynamometry in assessing knee extensor strength in inpatients undergoing rehabilitation after hip fracture and to examine the discriminant validity of this measure. Design: A total of 16 subjects (114 women; mean +/- SD, 79 +/- 7 yrs) undergoing inpatient rehabilitation after hip fracture volunteered to participate. Isometric knee extensor strength of the fractured and unfractured sides was determined with a hand-held dynamometer. Subjects were retested 1-2 days after the initial testing session. Results: Test-retest intraclass correlation coefficients were high for both the fractured (0.91) and unfractured legs (0.90). A low coefficient of variation was observed for both the fractured (15.3%) and unfractured (14.7%) sides. The maximal knee extensor strength was significantly different when comparing the fractured (7.9 +/- 3 kg) and unfractured (15.6 +/- 4 kg) legs. When comparing test 1 and test 2 mean values for the fractured leg, the scores significantly differed (t = 3.14, P < 0.01), with 13 of 16 subjects scoring higher on test 2. Conclusions: Hand-held dynamometry is a reliable and valid tool for assessment of knee extensor strength after hip fracture. Reduced knee extensor strength in the fractured leg may be an important component limiting rehabilitation progress in these patients.