1. A part of the body where bones are connected; such as, the knee, the elbow, or the skull.

Many joints have supporting ligaments, protective cartilage, and a particular range of movement, while others; such as, those between the bones of the vault of the skull are immobile.
2. The place at which two things, or separate parts of one thing, are joined or united, either rigidly or in such a way as to permit motion; a juncture.
3. Done or produced together with others; such as, a joint investment.
4. To plane and to shape the edge of a board so that it fits with another edge to form a joint.
5. Any of the points of connection between movable segments of the body in an insect, spider, crab, or other invertebrate.
6. The part of a plant stem on which a leaf or branch grows.
7. A crack or fissure in a rock, without any looseness or displacement of the surrounding area.
8. Either of the creases between the spine and the front and back covers of a book; especially. a hardback.
9. A place where parts or pieces of something are joined together.
10. A large piece of meat which is prepared and cooked for several people; especially, that which is roasted.
11. A place of entertainment; such as, a nightclub, especially one considered cheap or disreputable.
12. A slang term for a prison or similar penal institution: "He spent the last two years in the joint."
13. A slang description of a cigarette containing marijuana: "He was caught smoking a joint as he was walking down the street."

1. An articulation or the point of connection between two bones or elements of a skeleton; especially, if the articulation allows motion.

An area where two bones are attached for the purpose of the movements of certain body parts and such a joint is usually formed with fibrous connective tissue and cartilage.

2. The point, or points, of a juncture between two bones which are classified according to either their construction or based on the degree of movements which they allow.

It is classified as being immovable (synarthrosis), slightly movable (amphiarthrosis), or freely movable (diarthrosis).

• Synarthrosis is a joint in which the two bones are separated only by an intervening membrane; such as, the cranial sutures.
• Amphiarthrosis is a joint that has a fibrocartilaginous disk between the bony surfaces (symphysis); such as, the symphysis pubis; or one with a ligament uniting the two bones (syndesmosis); such as, the tibiofibular articulation.
• Diarthrosis is a joint in which the adjoining bone ends are covered with a thin cartilaginous sheet and joined by a ligament lined by a synovial membrane, which secretes a lubricant.

Joints are also grouped according to motion:

• Ball and socket (enarthrosis, a joint in which the rounded head of one bone is received into a socket, or rounded cavity, in another bone that allows motion in any direction).
• Hinge (ginglymus, a hinge joint which is an articulation, allowing flexion and extension, or motion in just two directions like a door hinge; for example, the elbows and the ankles).
• Condyloid (a reference to a round bump, or articular surface, on a bone where it forms a joint with another bone).
• Pivot (trochoid, that which is capable of rotating aroung a central axis; resembling or functioning in the body like a pivot or pulley).
• Gliding joint (arthrodia, where the joint surfaces are flat and only allow a gliding motion; such as, some wrist and ankle articulations).
• Saddle joint (two saddle-shaped joints at right angles to each other or they permit movements of all kinds except for rotations).

Bones connected entirely by cartilage which allow only slight movements.

Cartilaginous joints exist where the ribs connect to the sternum or breast bone and these joints allow movements during breathing.

A type of synarthrosis in which the bones are united by cartilage consisting of fibrous joints and the cartilaginous joints in which the bones are held together by cartilage.

Two or more bones that are joined and which allow motion or articulation: The two parts of the skeleton that are fitted together in the spine are known as .

Each vertebra has two sets of facet joints in which one pair faces upward (superior articular facets) and one pair faces downward (inferior articular facets).

Facet joints are synovial in that each joint is surrounded by a capsule of connective tissue which produces a fluid to lubricate all of them so they can move or slide (articulate) with each other.

Inflexible layers of dense connective tissues that hold the bones tightly together.

In adults, these joints or sutures, do not allow any movement; while in new-born babies and very young children, some fibrous joints, or fontanelles known as "soft spots", are movable before they have solidified.

These fontanelles on a baby’s head enable the soft bony plates of the skull to flex during the second stage of labor making it possible for the head to pass through the birth canal.

As the baby matures, the sutures close and the fontanelles gradually harden and are usually completely hardened by the child's second birthday.

The point at which two bones meet between the femur (thigh bone) and the tibia (shin): The knee joint is a modified hinge or junction that is capable of slight rotation in a bent position.

Each of these wedge-shaped crescents of knee joints have shock absorbers that resist impacts when running, jumping, etc.

Violent rotational movements of the thighs or legs while the knee joints are flexed; as in, football, soccer, skiing, or other sports, can severely damage the menisci or cartilage disks when they are squeezed between the bones of the knee joints.

Any of the four projections that link one vertebra of the spine to an adjacent vertebra: Lumbar facet joints are increasingly held responsible for low back aches.

The lumbar facet joints are subjected to continuous stresses throughout life and by degeneration, reactive remodeling, and hypertrophy (enlargement); all of which can affect the joints.

An articulation between two bones; that is, the point of connection between two bones or elements of a skeleton; especially, if the articulation allows motion.

An area where two bones are attached for the purpose of moving body parts.

An articulation, or joint, is usually formed of fibrous connective tissue and cartilage and the joints are grouped according to their motion:

• A ball and socket joint.
• A hinge joint.
• A condyloid joint (a joint that permits all forms of angular movement except axial rotation).
• A pivot joint.
• A gliding joint.
• A saddle joint

Joints can move in four and only four ways:

• Gliding, one bony surface that glides on another without angular or rotatory movement.
• Angular, occurs only between long bones, increasing or decreasing the angle between the bones.
• Circumduction, occurs in joints composed of the head of a bone and an articular cavity, the long bone describing a series of circles, the whole forming a cone.
• Rotation, a bone that moves around a central axis without moving from this axis.

Joints where two bones articulate (come together) to allow a variety of motions where the union of the bony elements are surrounded by an articular capsule enclosing a cavity lined by a synovial membrane.

These joints include "ball and socket joints"; such as, the hips and shoulders that permit a wide range of movements in several directions; and the "hinge joints"; such as, the knees and elbows which allow movements primarily in one direction or plane.

Synovial joints consist of several components which make complex movements possible

• Synovial capsule, the outermost layer of strong fibrous tissue which resembles a sleeve as it surrounds the joint.
• Synovial membrane which lines the capsule and secretes synovial fluid.
• Synovial fluid, which flows within the synovial cavity, acts as a lubricant to make the smooth movement of the joint possible.
• Ligaments, bands of fibrous tissue that form joints by connecting one bone to another bone, or joining a bone to cartilage and complex hinge joints; such as, the knee, are made up of a series of ligaments which permit movements in different directions.
• Bursa (s), bursae (pl), a fibrous sac which acts as a cushion to ease movement in areas that are subject to friction; such as, in the shoulder, elbow, and knee joints; where a tendon passes over a bone.

This joint is formed at the back of the mouth where the maxillary and mandibular arches come together.

The maxillary arch, which is part of the skull, does not move. The mandibular arch, which is a separate bone, is the moveable component of this joint.