38 C.F.R. § 4.59
With any form of arthritis, painful motion is an important factor of disability, the facial expression, wincing, etc., on pressure or manipulation, should be carefully noted and definitely related to affected joints. Muscle spasm will greatly assist the identification. Sciatic neuritis is not uncommonly caused by arthritis of the spine. The intent of the schedule is to recognize painful motion with joint or periarticular pathology as productive of disability. It is the intention to recognize actually painful, unstable, or malaligned joints, due to healed injury, as entitled to at least the minimum compensable rating for the joint. Crepitation either in the soft tissues such as the tendons or ligaments, or crepitation within the joint structures should be noted carefully as points of contact which are diseased. Flexion elicits such manifestations. The joints involved should be tested for pain on both active and passive motion, in weight-bearing and nonweight-bearing and, if possible, with the range of the opposite undamaged joint.
38 C.F.R. §4.59