📖 Static demo — read-only snapshot
You’re browsing a static build of the Body IQ knowledge graph, so everything loads with no backend. A few things that need the live server are turned off here:
- Global search (sidebar) is disabled — it queries the API.
- The JSON API and the API “Try it” playgroundaren’t included.
- The data is a snapshot — it refreshes only when the demo is rebuilt, not live from the database.
Everything else — the body map, progression ladders, coverage heatmap, exercise finder, and all anatomy/exercise/source pages — works fully. The full app (live search + API + database) runs from the source on GitHub.
Thumb Extension (MCP)
Thumb Metacarpophalangeal Joint • Hand • sagittal plane
Straightening the thumb at the metacarpophalangeal joint.
Axis: medial-lateral
Normal Range of Motion
Normal thumb MCP extension is recorded as return to the 0-degree neutral position; AAOS and Norkin & White list no positive extension value. The AMA Guides allow up to about 10 degrees of hyperextension as normal, and individual passive hyperextension varies considerably.
Source: AAOS Joint Motion / Norkin & White 2016
Muscles (2)
| Muscle | Role | Notes |
|---|---|---|
| Extensor Pollicis Longus | Primary | — |
| Extensor Pollicis Brevis | Primary | Extends thumb at MCP joint |
Exercises (1)
Sources
- Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation — Biomechanics of Thumb Extension (MCP)