The joint space means the space inside the human joint. In the knee joint, for example, the middle of the knee is the cruciate ligament and the meniscus, above the meniscus is the femur and below the meniscus is the tibia; around the joint there are ligaments, bursae, synovial membranes, muscles, tendons, fat and many other structures, which are not closely connected when the knee joint is relaxed. Gaps in the joint make the joint more flexible, but if the joint loses its gaps, the resistance to the joint increases, which reduces the flexibility of the joint, just like when a room is filled with people and no one can move around in the room. There are also joint gaps, such as the spinal joint gaps, where many important structures such as nerves and blood vessels pass through to ensure that other structures such as nerves and blood vessels function properly.