38 CFR § 4.45 - The joints.
As regards the joints the factors of disability reside in reductions of their normal excursion of movements in different planes. Inquiry will be directed to these considerations:
(a) Less movement than normal (due to ankylosis, limitation or blocking, adhesions, tendon-tie-up, contracted scars, etc.).
(b) More movement than normal (from flail joint, resections, nonunion of fracture, relaxation of ligaments, etc.).
(c) Weakened movement (due to muscle injury, disease or injury of peripheral nerves, divided or lengthened tendons, etc.).
(d) Excess fatigability.
(e) Incoordination, impaired ability to execute skilled movements smoothly.
(f) Pain on movement, swelling, deformity or atrophy of disuse. Instability of station, disturbance of locomotion, interference with sitting, standing and weight-bearing are related considerations. For the purpose of rating disability from arthritis, the shoulder, elbow, wrist, hip, knee, and ankle are considered major joints; multiple involvements of the interphalangeal, metacarpal and carpal joints of the upper extremities, the interphalangeal, metatarsal and tarsal joints of the lower extremities, the cervical vertebrae, the dorsal vertebrae, and the lumbar vertebrae, are considered groups of minor joints, ratable on a parity with major joints. The lumbosacral articulation and both sacroiliac joints are considered to be a group of minor joints, ratable on disturbance of lumbar spine functions.