The thumb is stiff or locked in place, limiting its ability to move.
Medical records that document which joint or joints of the thumb are ankylosed — the carpometacarpal joint, the interphalangeal joint, or both — are central to the rating. A VA or private examination should include a measurement of how close the thumb pad comes to the fingers when you try to oppose them, since the two-inch gap is the dividing line between favorable and unfavorable ankylosis. Notes about whether any bone shows rotation or angulation also matter, because those findings can shift the evaluation toward an amputation rating.
Imaging such as X-rays can confirm the fixed position of each joint. If both joints are ankylosed, the images may show whether either is fixed in extension or full flexion. Statements from you or people who see you daily can show how the fixed thumb affects grip, pinch, writing, tool use, or other tasks at work and at home. If other fingers are also affected, examination findings for those digits support consideration of an additional evaluation for overall hand function.
Conditions that are often caused or made worse by this one. If you have any of these, they may be claimable as secondary service connection.
