Three structural classes. Look at what fills the space between the bones.
Three functional classes, from locked to free.
| Structure | Synarthrosis immovable | Amphiarthrosis slightly movable | Diarthrosis freely movable |
|---|---|---|---|
| Fibrous | Sutures (skull), gomphoses (teeth) | Syndesmoses (distal tibiofibular joint, interosseous membranes) | none |
| Cartilaginous | Synchondroses (epiphyseal plate, first sternocostal joint) | Symphyses (pubic symphysis, intervertebral discs) | none |
| Synovial | none | none | All synovial joints (shoulder, hip, knee, elbow, wrist...) |
Notice the pattern: the less a joint moves, the more stable it is. The more it moves, the easier it is to injure.
Tap a part in the list to light it up in the diagram. Every synovial joint has the same basic parts.
Each model shows the shape of the joint surfaces, the axes it can turn around (dashed lines), and the motion it allows (arrows). Blue caps are articular cartilage.
1Structure: what holds these bones together?
2Which kind?
3Function: how much can it move?
Drag each joint card into the right box: rows are structure, columns are function. No dragging? Tap a card, then tap a box. Some boxes stay empty in real life, and that is part of the lesson.
Cards to place (tap a placed card and then this tray to send it back)
What movement is this?
Which joint is doing the moving?
Which plane is the movement in?
Every movement is shown from anatomical position (standing, palms forward). Wrong answers just show you what to watch for.