Alternating compression and decompression of the joint cartilage supplies it with nutrients
There are various types of joint:
- saddle joints
- ball and socket joints and
- hinge joints
These ensure that we can move (around) harmoniously.
There are various types of joint in the human body: hinge joints in the knees, elbows and fingers; a pivot joint between the radius and ulna and saddle joints at the base of the thumbs. Ball and socket joints provide for movement of the hip and shoulder joints.
Joints generally consist of a joint head and a socket. These are separated by a layer of cartilage. The joint capsule surrounds the joint and, together with ligaments, tendons and muscles, forms a protective outer envelope.
The synovial membrane lines the capsule and supplies the joint space with synovial fluid that provides the cartilage with nutrients. In rheumatoid arthritis, for example, the synovial membrane begins to proliferate strongly and fluid leaks out of the blood vessels. After some time, this proliferation begins to attack the cartilage, bone and ligaments.
The articular cartilage covers the ends of the bones and can both even out irregularities in the joint surfaces and absorb impacts due to its plasticity. The constant alternation between loading and unloading ensures a constant supply of nutrients to the articular cartilage to keep it healthy.
The range of movement depends not only on the geometry of the joint, but is also controlled by the surrounding structures (muscles, ligaments, capsule).
Arthritis: a common joint disorder
The synovial membrane lines the capsule and supplies the joint space with synovial fluid that provides the cartilage with nutrients. In rheumatoid arthritis, for example, the synovial membrane begins to proliferate strongly and fluid leaks out of the blood vessels. After some time, this proliferation begins to attack the cartilage, bone and ligaments.