Final answer:
The least movable joints are immovable joints, which include fibrous connections such as those in the skull, as well as joints between certain bones in the arm and leg, allowing little to no movement.
Step-by-step explanation:
The least movable joints are immovable joints. These joints allow little to no movement and are primarily the fibrous joints found in the body. Among the immovable joints are those that make up the bones of the cranium, securing the skull bones tightly together. The joints between the tibia and fibula in the lower leg and between the radius and ulna in the forearm are other examples of immovable joints. In contrast, partly movable joints, such as those between the vertebrae and between the ribs and sternum, permit slight movement. The most common joints in the body, however, are movable joints, such as the shoulders, hips, elbows, and knees, which are also known as synovial joints and allow a wide range of movements.