Chapter 17, The Lower Extremities, in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth Edition, continues to provide three means of assessing impairment: anatomic, diagnostic, and functional. Changes from the AMA Guides, Fourth Edition, include the following: The principles of assessment have been expanded to clarify when the different evaluation methods should be used (eg, less specific functional methods typically should not form the basis for a rating if more specific anatomic or diagnostic methods are available). A new cross-usage chart, Guide to the Appropriate Combination of Evaluation Methods (Table 17-2), indicates which methods can and cannot be appropriately used in combination. The evaluation of causalgia and complex regional pain syndrome now follows the same principles used to evaluate central nervous system lesions, and additional case examples are provided. Corresponding tables from the AMA Guides, Fourth and Fifth Editions, are compared. Guidance is provided about how to approach range-of-motion deficits in multiple directions in the same joint, and additional tests are discussed. Finally, the chapter provides Figure 17-10, Lower Extremity Impairment Evaluation Record and Worksheet, a useful template to simplify making the assessment and recording the evaluation, along with six case examples.