What Are Semi-Mobile Joints?

Generally speaking, joints are the connections between two bones or between a bone and cartilage. Scientists who study bones, arthrologists, employ two classification schemes for joints. In one of these systems, range of motion determines the type of joint. One type of joint, a synarthrosis, is completely immovable. A second type, a diarthrosis, allows for a large range of motion. Lying in between these two extremes are amphiarthroses, or semi-mobile joints.

Types of Semi-Mobile Joints

• Semi-mobile, or semi-movable joints, permit a limited range of motion. These joints can be divided into two types based on their structures. A syndesmosis is a fibrous semi-mobile joint. In this type of joint, a strong band of fibrous connective tissue, called an interosseous ligament, connects the bones. A symphysis is a cartilaginous semi-mobile joint, with cartilage connecting two bones.

Syndesmoses

• The two bones that make up the lower leg, the tibia and the fibula, as well as the two bones that make up the lower arm, the radius and the ulna, are connected by interosseous ligaments. The syndesmoses provide stability to the lower arm and leg while simultaneously allowing movements in the wrist, hand, foot and ankle.

Pubic Joint

• At the front of the body, the two pelvic halves join together with the help of a cartilage disk and the interpubic ligaments. This symphysis allows the two halves of the pelvis to move independently, with a small range of motion. The range of motion is enough to absorb shock while you run and walk, and, for women, is large enough to give birth.

Vertebral Column

• In your vertebral column, you have 33 vertebrae. These vertebrae are connected by intervertebral disks made of cartilage. These symphyses give a limited amount of mobility between any two vertebrae. However, the combined motion of each of these symphses allows you to flex and extend your spine with ease.