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The location where two bones come together in the body is known as a joint. There are three main types of joints in the human body, fibrous, cartilaginous, and synovial. Fibrous joints are stationary and do not allow for movement between the articulating bones. Cartilaginous joints allow for slight movement between the touching bones, and synovial joints provide a free range of movement between the converging bones.
Of all the joints in the human body, the fibrous joint is the least flexible. In these fixed joints, two bones are connected and held together with connective tissue or ligaments. There are three types of fibrous joints in the human body, sutures, syndesmosis, and gomphosis. Sutures fibrous joints are found between the bone plates in the skull, and syndesmosis fibrous joints can be found in the back where broadly separated vertebrae are linked together. Gomphosis fibrous joints are used to hold an immobile bony process inside a socket, as occurs in a tooth in a tooth socket.
Cartilaginous joints connect two bones together using cartilage and allow for limited mobility. There are two types of cartilaginous joints in the human body, symphysis and synchondrosis. Symphysis cartilaginous joints are permanent joints that use hyaline cartilage to connect the bones. An example of a symphysis joint is the pubic symphysis formed where the bottom of the left and right pelvic bones meet.
Synchondrosis cartilaginous joints are similar to symphysis joints except that these joints are occasionally temporary. In some parts of the body, the hyaline cartilage is transformed into bone during childhood growth. An example of this type of transforming joint is found at the base of the tibia bone in the leg.
The synovial joints are the most flexible types of joints in the human body. To allow for the assorted movements needed in the body, this joint comes in a seven different variations. Hinged, pivot, ball and socket joints allow for flexible and wide-ranging movement while gliding, compound, condyloid, and saddle joints are slightly less flexible. Joints that are hinged allow for movement similar to a hinge on a door and work to bend and unbend various body parts. An example of a hinge joint is the elbow.
A synovial pivot joint allows for the revolution of one bone around another. The neck is an example of a pivot joint. The ball and socket joint occurs between a bone ending in a ball shape and another concave bone. This joint allows for a wide range of movements and can be found in the hip. A gliding joint enable two bones to slip across one another, as can be found in some of the joints in the hand. The knee is an example of a compound joint that allows three or more bones to move together.
The condyloid joint occurs where two articulating bones have a unique but complementary shape. In this type of joint, one bone often has a bowl shape and the other bone has a process that fits into the bowl shape. Several condyloid joints can be found in the wrist. A saddle joint is similar in structure to a condyloid joint, but the shape of the bones resembles a saddle and rider. An example of this type of joint can be found in the thumb.