Joint Classification — Visual Reference
Three Major Joint Types
| Classification | Technical Name | Movement | Examples |
|---|---|---|---|
| Fibrous | Synarthrosis | Immovable | Skull sutures, gomphosis (teeth in socket) |
| Cartilaginous | Amphiarthrosis | Slightly movable | Pubic symphysis, intervertebral discs |
| Synovial | Diarthrosis | Freely movable | See 6 subtypes below |
Six Synovial Joint Subtypes (Must Memorize ALL)
| Subtype | Description | Example | Movement Allowed |
|---|---|---|---|
| Hinge | Convex fits into concave | Knee, elbow | Uniaxial: flexion + extension |
| Pivot | Peg rotates in ring | Atlas-axis (C1-C2), proximal radioulnar | Rotation only |
| Ball-and-socket | Sphere in cup | Shoulder (glenohumeral), hip | Multiaxial: all planes + rotation |
| Gliding (plane) | Flat surfaces slide | Intercarpal, intertarsal | Sliding in multiple planes |
| Saddle | Two concavo-convex surfaces | Thumb CMC (carpometacarpal) | Biaxial: 2 planes, no rotation |
| Ellipsoid (condyloid) | Oval in elliptical socket | Wrist (radiocarpal), knuckles | Biaxial: 2 planes, no rotation |
Key Distinction: Saddle vs Ellipsoid
Both allow biaxial movement without rotation. The thumb CMC is the ONLY saddle joint example in NEET. The wrist is the classic ellipsoid example. The key structural difference: saddle has two concavo-convex surfaces (like two saddles interlocked); ellipsoid has one oval surface fitting into one elliptical socket.
Memory Aid
"Happy People Ball Glide Sideways Easily" — Hinge, Pivot, Ball-and-socket, Gliding, Saddle, Ellipsoid.