The process of assessing lower extremity impairment described in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, differs from that in previous editions. This article addresses common questions that arise in knee and hip impairment rating according to the new edition. Anatomic, diagnostic, or functional methods can be used to estimate lower extremity impairments. Functional methods include ratings based on diminished range of motion, weakness, or gait derangement. In general, only one method should be used to rate impairment associated with an injury or illness. Section 3.2i, Diagnosis-related Estimates, in the AMA Guides lists impairment ratings for many knee conditions and operative procedures. Decreased range of motion, ankylosis, diminished muscle function, and joint space narrowing are some rating methods for the knee. Similar anatomic, diagnostic, and functional methods may be used to rate impairment due to hip pathology, but most hip impairments are estimated by range-of-motion deficits. Assessing lower extremity impairments requires a thorough medical evaluation, careful analysis, experience, and clear judgment; evaluators must determine the applicable rating methods, use the methods to rate the impairment, and then decide which method or combination best describes the impairment, without overlooking or duplicating ratings. [A related Lower Extremity Impairment Checklist and Worksheet appears on page 4 of this issue of The Guides Newsletter. A related Quick Reference, Motion at the Wrist, Elbow, and Shoulder, appears on page 5.]

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