Which type of joint is immovable (fixed) and found in the cranium and distal tibiofibular joint?

• A. Fibrous (synarthrodial)
• B. Synovial (diarthrodial)
• C. Cartilaginous (amphiarthrodial)
• D. Bony (synostosis)

Answer: (A)

The movement of a joint is determined by the tissue that binds it and how much it allows. Immovable joints are synarthroses, and they’re typically fibrous, held together by dense collagen. In the cranium, the skull bones are joined by sutures—dense fibrous connections that cement the bones together and permit essentially no motion. The distal tibiofibular joint is a fibrous connection (a syndesmosis) held by ligaments between the tibia and fibula; in adults this joint provides stability with negligible movement. So, when a question points to immobility and examples like the skull sutures and a distal tibiofibular connection, the fibrous synarthrodial category is the best fit. Other joint types involve fluid-filled capsules (synovial joints that move freely) or cartilage bridges with limited movement (cartilaginous joints), and a fully fused bone (bony synostosis) is a different end state that isn’t what these examples illustrate.