The Difference between Active Extension Lag and Passive Flexion Contracture After Total Knee Replacement - Rating Tip of the Month

When rating Impairment of the lower extremity after Total Knee Replacement, an examiner must know to examine and document both passive and active motion in the knee so as insure measurement of Extension Lag and Flexion Contracture, if present. These terms are not interchangeable.

Extension Lag is defined as the maximum extension measurement when performing active motion testing. Flexion Contracture is the maximum extension measurement when performing passive motion testing.

These values can be the same but can also be different. An example being if an examinee has -10 degrees of active extension lag but only -5 degrees of passive flexion contracture. Under Table 17-35 (5th Ed., p 549), these values would have separate deduction values since they are not identical in measurement.

A circumstance discussed in The Guides Casebook on page 309 documents another situation when active extension lag and passive flexion contracture are identical in measurement. In this case, no points would be deducted for extension lag as the flexion contracture deduction would adequately consider the loss of full extension.