Identifying Types of Joints - Anatomy

Joints allowing a great range of motion require lubrication. This lubrication is provided by sinovial fluid, which is present in sinovial joints. The fluid is encased inside a membrane to provide this lubrication, allowing a greater degree of motion.

Fibrous joints and suture joints are significantly less mobile, while cartilaginous joints are somewhat less mobile. Synarthrosis is a term used to describe any type of joint that does not allow for motion.

The atlantoaxial joint connects the C1 vertebra (atlas) and the C2 vertebra (axis). This joint allows for side-to-side turning of the head, classifying it as a pivot joint. The atlantoaxial joint has the greatest range of motion of any intervetebral joints in the body.

The humeroulnar joint is a a hinge joint (the elbow), capable of flexion and extension in a single plane. The sternoclavicular joint is a saddle joint joining the medial end of the clavicle to the sternum. The acromioclavicular joint is a gliding joint joining the distal end of the clavicle to the acromion process of the scapula. The glenohumeral joint is a ball and socket joint securing the proximal end fo the humerus to the glenoid fossa of the scapula.

Synchondroses are joints connecting two bones by a band of cartilage. Commonly, this type of joint is found at the ends of developing long bones between the diaphysis and epiphyses, where a thin band of cartilage is responsible for bone growth during intramembranous ossification. This joint eventually fuses as growth ends. In contrast, the ribs are connected to the sternum via permanent synchondrosis joints: the costochondral joint, which joins the rib and the cartilage band, and the sternocostal joint, joining the cartilage and the sternum.

Syndesmosis joints are held together by bands of connective tissue (ligaments), but lack the synovial fluid and capsule structure of a synovial joint. This limits their mobility; while some motion between the bones is possible, the joint is fairly rigid. The inferior (or distal) tibiofibular joint is a syndesmosis in which the tibia and fibula are connected near the ankle. Damage to this joint is known as a high ankle sprain.

Cartilaginous joints encompass the classifications of synchondroses and symphyses. Synchondroses are cartilaginous joints in which bones are joined by hyaline cartilage, while symphyses are joined by fibrocartilage. The pubic symphysis is a cartilaginous joint that connects the pelvic bones via fibrocartilage.

Synovial joints are surrounded by a joint capsule, which holds the joint in a matrix of synovial fluid. This fluid provides the joint with lubrication for a wide range of motion. Many of the joints commonly associated with movement and locomotion are synovial joints. The intercarpal joints, found between the bones of the wrist, are synovial joints.

These are all types of synovial joints, defined by their apparent shapes and mechanisms of motion. For example, the knee is a hinge joint, which allows flexion and extension along a single axis, but not adduction or rotation.

Ginglymus joints are also known as hinge joints, which only permit flexion/extension movements. The humeroulnar joint of the elbow is the best example of this. Cotyloid and ball and socket joints are synonymous, and permit motion in all three planes. Pivot joints and lateral ginglymus are synonymous, and permite transverse plane movement.

There are only two ball and socket joints in the human body. They are the hip and the shoulder joints (there are two in the hip and one in each shoulder). Of the two areas where there are ball and socket joints, the shoulder is the weakest. More shoulder dislocations occur than any other joint. The greater the range of movement, generally the weaker the joint is. Unlike the hip which has a deeper depression for the femur to fit into, the shoulder joint has a relatively shallow depression for the humerus to fit into. This coupled with its weaker tendons makes it the weaker of the two ball and socket joints.

The shoulder is a ball and socket joint, which allows a wide range of movement. The elbow is a hinge joint, which only allows movement in one plane. The thumb is a saddle joint, which allows movements in a variety of directions. Finally, the knuckles are a condyloid joint which is a rounded bone moving within a shallow "bowl" shape of another bone.

Diarthroses like the elbow and knee allow free movement. Amphiarthroses allow slight movement and are found in areas where flexibility is needed, but a lot of flexibility would be unwanted such as the vertebral joints. Synarthroses allow no movement. The sutures of the skull are an example.

The shoulder and the hip form the only ball-and-socket joints in the entire human body. Ball-and-socket joints give rise to multidirectional movement of all types except for gliding. Hinge joints, such as the elbow and knee, can only move in one plane. Pivot joints, such as the radioulnar joints allow rotation. Plane/gliding joints only allow gliding movements.

Synovial joints contain a synovial cavity that contains synovial fluid. This joint structure allows for many different types of movement. Neither cartilaginous nor fibrous joints contain fluid-filled cavities.

A diarthrosis is another name for a synovial joint. Synovial joints (diarthroses) allow more movment than synarthroses. The tibiofemoal joint (the knee), the humero-ulnar joint (one of the elbow joints), and the glenohumeral joint ("the shoulder") are all synovial joints. Although the proximal tibiofibular joint is a diarthrosis, the distal tibiofibular joint is not; it is a type of synarthrosis.

Intra-articular discs are structures made of fibrocartilage that increase joint congruency, and improve shock absorption. They can be found in the AC joint, the SC joint, the TMJ, and several other joints. Similarly, the acetabular labrum in the coxafemoral joint is comprised of fibrocartilage, and improves joint congruency. However, it is not an intra-articular disc.

The knee is composed of the femur and the tibia, which creates a hinge joint. The ball in socket would be the shoulder or hip, composed of a ball like structure that rotates around a socket like bone. The saddle joint is a special joint located in the thumb and allows for multiple motions. A plateau joint does not exist in the body.

Fibrous joints, also known as synarthroses, are joined by fibrous tissue, have no joint cavity, and allow little movement. An example of this is a suture, which is found between the flat bones of the skull. Cartilaginous joints are joined by cartilage, have no joint cavity, and allow little or no movement. An example of this is the epiphyseal plate. Synovial joints, in contrast, do contain a joint cavity and allow a great deal of free movement. An example of this is the hip joint.

The sternoclavicular and trapeziometacarpal (thumb) joints are unique in that the involved bones have both convex and concave portions that give their saddle shape.

Gliding joints, also called plane joints, have flat articular surfaces that allow movement in all different directions. (There are eight carpal bones in the wrist: scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate.)

Ball and socket joints, such as the glenohumeral joint in the shoulder and acetabulofemoral joint in the hip, allow for the widest range of movement.

A syndesmosis is a type of immovable fibrous joint that is made up of collagen. This same interosseous membrane also exists between the radius and ulna. Sutures and gomphoses are other examples of fibrous joints.