In anatomy, the term "articulation" refers to an arrangement of structures that keeps two or more contiguous bony surfaces together. Thus, articulation represents a set of elements (fibrous tissue and/or cartilage, ligaments, capsules, membranes) that regulate the connection between two skeletal segments.
A joint is a point in the body where bones meet. They make movement possible by making the skeleton flexible. The main bones that form the joints include the following:
- Synovial joints: knee, wrist, shoulder, elbow, ankle, and hip joints
- Semi-mobile joints: articulation of the spine
- Fixed joints: joints of the bones of the skull or pelvis
Joints are classified by how much movement they allow (function) or what they are made of (structure). Most allow free movement, some only allow movement in certain ways and others allow no movement. By use of scientific terminology, we speak respectively of synovial joints, synarthrosis joints and amphiarthrosis joints.
In regards to joint disorders, the three most common types include: osteoarthritis, arthritis, and traumatic injuries. Osteoarthritis is the most common joint disorder and occurs when the joints become swollen and more difficult to move. Arthritis refers to a joint condition that causes inflammation of one or more joints. Traumatic injuries are characterized by two bones separating from their meeting point. They may caused by a fall, sudden impact or other form of trauma. Other disorders may involve cancers and birth defects (such as hip dislocation).
What are moveable joints?
Synovial joints, also known as movable joints, refer to the joints that are capable of moving in a variety of directions (allow mobility). Such examples include the knee joints, elbow joints, wrist joints, shoulder joints, hip joints and ankle joints. The joint surfaces are smooth, covered with cartilage, and gathered in a so called joint capsule. The joint capsule is a fibrous connective tissue which ensures that the joint is secure. Externally, it is surrounded by a fibrous membrane which is capable of secreting and reabsorbing the synovial fluid (colorless, viscous substance), whose role is to fill the joints to keep them lubricated and make them move more easily.
What function do moveable joints serve?
The main function of the joints is to allow both movement and flexibility. They tend to be classified by the degree of their possible movement, the number of bones involved and the complexity of the joint.
The main function of the movable joints is to allow the execution of a wide range of movements, as in the case of the knee joint or the elbow joint. The types of synovial joints are based on the shapes and can be classified in various forms: flat, spherical, ellipsoidal- and are typically consistent (embracing each other).
The six different types of synovial joints include the following:
- Condyloid joints (ex: the wrist joint)
- Plane joints (ex: some joints in the foot and wrist)
- Hinge joints (ex: knee, elbow and finger joints)
- Saddle joints (ex: base of the thumb)
- Pivot joints (ex: the first and second vertebrae of the neck that allows the head to move back and forth)
- Ball-and-socket joints (ex: shoulder and hip joints)
