Synovial joints have greater flexibility than fixed (fibrous) and cartilaginous joints primarily because of their unique structural features. Synovial joints contain a joint cavity filled with synovial fluid, which acts as a lubricant, reducing friction between the bones and allowing smooth, free movement. These joints also have articular cartilage covering the ends of the bones, helping absorb shocks and providing a smooth surface for flexible motion. Additionally, ligaments around synovial joints provide stability while still permitting a wide range of motion. In contrast, fixed joints like those in the skull are immovable, designed mainly for stability rather than flexibility. Cartilaginous joints, which connect bones with cartilage, allow limited movement and provide more stability than synovial joints but less flexibility. The absence of a joint cavity, synovial fluid, and the restricted nature of cartilage limit their range of motion compared to synovial joints. Thus, the combination of a lubricated joint cavity, protective cartilage, and flexible yet stabilizing ligaments in synovial joints collectively enables them to have greater flexibility than fixed and cartilaginous joints.
