Diagnostic Code 5224 · 38 CFR §4.71a
Ankylosis of the thumb means complete loss of motion in the thumb joints. The thumb is responsible for approximately 40% of hand function due to its opposition capability. Loss of thumb motion significantly impairs pinch grip, grasping, and fine motor tasks. The rating depends on whether the ankylosis is in a favorable position (thumb can still be used somewhat for grasping) or unfavorable position (thumb is fixed in a position that prevents functional use).
| Rating | Criteria |
|---|---|
| 20% | 20% — Favorable ankylosis: thumb fixed but in a functional position |
| 30% | 30% — Unfavorable ankylosis: thumb fixed in a non-functional position |
Medical records documenting complete loss of motion (ankylosis) in the affected finger joints. X-rays or imaging showing joint fusion or fixation. Range of motion testing showing zero degrees of motion. Documentation of whether ankylosis is in favorable or unfavorable position. Service treatment records or nexus opinion linking the condition to military service.