Criteria: Table 17-4 Leg Length Discrepancy (528); Table 17-5 Lower Limb Impairment Due to Gait Derangement (529); Table 17-6 Impairment Due to Unilateral Muscle Atrophy (530); Table 17-8 Impairment Due to Lower Extremity Muscle Weakness (532); Table 17-9 Hip (537), Table 17-10 Knee Impairment (537), Table 17-11 Ankle Motion Impairment Estimates (537),Table 17-12 Hindfoot Impairment Estimates (537), Table 17-13 Ankle or Hindfoot Deformity Impairments (537), and/or Table 17-14 Toe Impairments (537); Table 17-31 Arthritis Impairments Based on Roentgenographically Determined Cartilage Intervals (544). Measurements should be compared to the opposite extremity; Table 17-32 Impairment Estimates for Amputations (545); Table 17-33 Impairment Estimates for Certain Lower Extremity Impairments (546-547); Table 17-36 Impairment for Skin Loss (550): Table 17-37 Impairments Due to Nerve Deficits (552); Table 17-38 Lower Extremity Impairment Due to Peripheral Vascular Disease (554).
Guidance: The process of assessing lower extremity permanent impairment is described in Chapter 17 Lower Extremities (523-564). Thirteen methods can be used to assess the lower extremities. The Guides state: “Typically, only one method will adequately characterize the impairment and its impact on the ability to perform ADL.” (527) A cross-usage chart (Table 17-2, 526) indicates which methods and resulting impairment ratings may be combined. The approaches include: 17.2b Leg Length Discrepancy: This approach is rarely used to assess impairment, unless there is documented significant shortening of the leg due to the injury, in which case Table 17-4 (528) is applicable. 17.2c Gait Derangement: This is a stand-alone methodology and rarely is applicable. In an unusual case where there is not other basis impairment is based on Table 17-5 Lower Limb Impairment Due to Gait Derangement (529), The Guides state: “Whenever possible, the evaluator should use a more specific method. When the gait method is used, a written rationale should be included in the report. The lower limb impairment percents shown in Table 17-5 stand alone and are not combined with any other impairment evaluation method. Section 17.2c does not apply to abnormalities based only on subjective factors, such as pain or sudden giving-way, as with, for example, an individual with low-back discomfort who chooses to use a cane to assist in walking.” (529) 17.2d Muscle Atrophy, 17.2e Manual Muscle Testing: Table 17-6 Impairment Due to Unilateral Muscle Atrophy (530) is used to rate atrophy (measurements are compared 10 cm. above the patella and at the maximum circumference of the calf) and Table 17-8 Impairment Due to Lower Extremity Muscle Weakness (532) is used to rate weakness, when the finding of muscular weakness is consistent. 17.2f Range of Motion: Section 17.2f states “Lower extremity impairment can be evaluated by assessing the range of motion of its joints, recognizing that pain and motivation may affect the measurements. If it is clear to the evaluator that a restricted range of motion has an organic basis, three measurements should be obtained and the greatest range measured should be used. If multiple evaluations exist, and there is inconsistency of a rating class between the findings of two observers, or in the findings on separate occasions by the same observer, the results are considered invalid. Figures 17-1 to 17-6 illustrate one method of measuring range of motion in the lower extremity. The ranges listed in Tables 17-9 through 17-14 are examples of mild, moderate, and severe impairments and are to be used as guides. Range-of-motion restrictions in multiple directions do increase the impairment. Add range-of-motion impairments for a single joint to determine the total joint range-of-motion impairments.” Depending on the joints involved, the following tables may used: Table 17-9 Hip (537), Table 17-10 Knee Impairment (537), Table 17-11 Ankle Motion Impairment Estimates (537), Table 17-12 Hindfoot Impairment Estimates (537), Table 17-13 Ankle or Hindfoot Deformity Impairments (537), and/or Table 17-14 Toe Impairments (537). 17.2g Ankylosis: This is less common approach, except for surgical fusions. Optimal fusion of an ankle results in 4% whole person permanent impairment or 10% lower extremity permanent impairment. 17.2h Arthritis: Ratings are based on radiographic findings and the use of Table 17-31 Arthritis Impairments Based on Roentgenographically Determined Cartilage Intervals (544). Measurements should be compared to the opposite extremity. 17.2i Amputations: Based on Table 17-32 Impairment Estimates for Amputations (545). 17.2j Diagnosis-based Estimates: Specific conditions are rated per Table 17-33 Impairment Estimates for Certain Lower Extremity Impairments (546-547). 17.2k Skin-loss: Less commonly used; based on Table 17-36 Impairment for Skin Loss (550). 17.2l Peripheral Nerve Injuries: Based on Table 17-37 Impairments Due to Nerve Deficits (552) specifies maximum loss for motor, sensory, and dysesthesia deficits. Deficits are graded using Table 16-10 (5th, 482) for sensory deficits and 16-11 (484) for motor deficits. 17.2m Causalgia and Reflex Sympathetic Dystrophy: The process defined in the Section 13.8 Criteria for Rating Impairments Related to Chronic Pain (343-344), Chapter 13, The Central and Peripheral System is used to rate complex regional pain syndrome (causalgia and RSD). 17.2n Vascular Disorders: Based on Table 17-38 Lower Extremity Impairment Due to Peripheral Vascular Disease (554). The final rating is typically based on a single method.
