Workers who kneel for major portions of their workday (eg, floor and roof installers) may be prone to inflammation of the knee bursae and patellofemoral pain. In the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), range-of-motion (ROM) and diagnosis-based impairment (DBI) are the two possible stand-alone methods for rating knee impairment. The ROM method was widely used in previous editions of the AMA Guides, but at present DBI is the method of choice for calculating impairment. To rate knee impairment using the DBI method, the physician first chooses the appropriate diagnosis from the Knee Regional Grid in the AMA Guides, Sixth Edition. Next, the physician chooses the appropriate impairment class for the diagnosis and then selects the appropriate grade modifiers. The physician applies the net adjustment formula to determine lower extremity impairment and finally converts the final lower extremity impairment to whole person impairment. Two or more conditions often are found in the knees and require causation analysis in which the physician should choose the single causally related diagnosis that will yield the highest impairment rating. Modifiers should be chosen based on reliable findings that have not been used previously to assign either the diagnosis or impairment class. The ROM method can be used to select the physical examination grade modifier or as a stand-alone rating if the physician offers a rationale that is supported by the AMA Guides.