Joints may be classified based on the articulation surfaces involved:
- simple joints - when two articulation surfaces meet (e.g. shoulder joint)
- compound joints - when three or more articular surfaces are involved (e.g. radiocarpal joint)
- complex joints - when 2 or more articular surfaces and an articular disc or meniscus are involved (e.g. knee joint)
Synonym: articulation joint, facies articularis.