The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, takes approaches to the lower extremities that are consistent with Chapter 15, Upper Extremities (reviewed in the March/April 2008 issue of The Guides Newsletter). Because there is a comparatively smaller spectrum of diagnoses in the lower extremities, Chapter 16 is less complex and is shorter than Chapter 15. The purposes of the lower extremity are transfer and mobility, and, in comparison to the upper extremity, the lower extremity provides greater stability than flexibility. This chapter's principles of assessment define the standards for interpreting symptoms and signs, functional history, physical examination, and clinical studies. Examiners may use the Lower Limb Instrument developed by the American Academy of Orthopaedic Surgery as an adjunct to defining functional ability, but values are not provided to define a specific grade modifier. Most lower extremity impairments are based on Diagnosis-related impairments, and an impairment example case demonstrates the use of the Knee Regional Grid to asses a partial meniscus repair. An associated table illustrates the resulting whole person impairment values associated with these examples and gives the probable impairments based on the fifth edition. The article also discusses impairments of the peripheral nerves, amputation, and range of motion. Mastery of one chapter of the AMA Guides facilitates performing ratings using other chapters.