All joints
Joint guide
Thumb digit (ray) — overview
The thumb has three main levels: the saddle joint at the base, the knuckle (MCP), and the end hinge (IP). Together they let the thumb oppose the fingers for power and fine pinch.
Diagram
Schematic for orientation — not a substitute for imaging or an in-person exam.
Related joints
Related anatomy topics
Sources & further reading
We cite major society patient education, NIH institute pages, and MedlinePlus for naming and general joint context. Links open in a new tab; access dates help you judge currency when guidelines update.
- Arthritis of the thumb (thumb CMC / basal joint context) — OrthoInfo — American Academy of Orthopaedic Surgeons(accessed 2026-04-24)
- Hand and wrist anatomy — American Society for Surgery of the Hand(accessed 2026-04-24)
- Hand problems and arthritis — National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH)(accessed 2026-04-24)