Factors related to extension lag at the knee joint

Twenty patients were examined in an investigation of the relationships between extension lag at the knee and other measures taken from the injured and uninjured extremity. The results of the study show: 1) there were no significant correlations between extension lag and the depth of squat, the extension force or flexion force, the circumference at the joint line or the circumference 5 and 15 centimeters cephalad to the patella pole, and active or passive knee flexion; 2) that the mean for flexion force was greater than the mean for extension force in the injured extremity, and there was no difference between the means for flexion and extension force in the uninjured extremity; and 3) that the means of the measures for active and passive flexion, flexion force, and circumference measures of the thigh taken from a group of patients who had stiff rotational movements at the tibiofemoral joint.were different from the means of the same measures taken from a group of patients who had normal rotational movements. There is limited evidence to suggest that weakness of the quadriceps muscle may be a factor in extension lag at the knee, but the support for this conclusion is based on comparison between groups of patients and not from the correlations between other variables and extension lag. For future studies, it is recommended that an attempt be made to secure patients with extension lags greater than 3Oin an effort to improve the prospect of detecting any relationships.J Orthop Sports Phys Ther 1982;3(4):178-182.