Relationship between hardness and deformation of the vastus lateralis muscle during knee flexion using ultrasound imaging.

The aims of this study were to clarify the relationship between deformation of the VL during knee flexion and the stiffness of the VL. 40 lower limbs of 20 male normal volunteers were divided into control and tightness groups using the Ely test. Deformation of the VL in the transverse plane during active knee flexion from 0 to 90° was recorded using B-mode ultrasonography. Hardness of the VL was measured on the middle lateral thigh using a durometer. The reaction force at fully passive flexion was measured using a hand held dynamometer. The deformation of the VL and the hardness and passive torque showed significant differences between the 2 groups. The deformation of the VL showed a significantly higher correlation with hardness of the VL. Measurements of the deformation of the VL might be predicted by the elasticity around the VL.