Classification of Joints

Inner Synovial Membrane

Composed of areolar connective tissue with elastic fibers.

Two principle interosseous membrane joints

(1) Between the radius and ulna in the forearm (2) Between the tibia and fibula in the leg

Structural classification of joints

(1) the presence or absence of a space between the articulating bones called synovial cavity (2) the type of connective tissue that holds bones together

Movement of joints is determined by

(1) the shape of the articulating bones (2) the flexibility (tension or tautness) of the ligaments that bind the bones together (3) the tension of associated muscles and tendons

Synovial Joint is immovable

the fluid is quite viscous (gel-like), but as joint movement increases, the fluid becomes less viscous.

Synchondrosis

A cartilaginous joint in which the connecting material is hyaline cartilage. Functionally, a synchondrosis is a synarthrosis, an immovable joint. When bone growth stops, bone replaces the hyaline cartilage.

Symphysis

A cartilaginous joint in which the ends of the articulating bones are covered with hyaline cartilage, but the bones are connected by a broad, flat disc of fibrocartilage. Functionally, a symphysis is an amphiarthrosis, a slightly movable joint.

Suture

A fibrous joint composed of a thin layer of dense irregular connective tissue. Sutures unite the bones of the skull. Amphiarthrosis in infants and children. Synarthrosis in older adults.

Syndesmosis

A fibrous joint in which there is a greater distance between the articulating surfaces and more dense irregular connective tissue than in a suture. It permits slight movement so it's classified as Amphiarthrosis.

Diarthrosis

A freely movable joint. The plural is diarthroses. Types are gliding, hinge, pivot, condyloid, saddle, and ball-and-socket

Bursae

A sac or pouch of synovial fluid located at friction points, especially about joints. Bursae are not strictly part of synovial joints, but do resemble joint capsules because their walls consist of connective tissue lined by a synovial membrane.

Amphiarthrosis

A slightly movable joint. The plural is amphiarthroses.

Interosseous Membrane

A substantial sheet of dense irregular connective tissue that binds neighboring long bones and permits slight movement (amphiarthrosis).

Synarthrosis

An immovable joint. The plural is synarthroses.

Ligaments

Fibers of some fibrous membranes are arranged in parallel bundles that are highly adapted for resisting strains. The main mechanical factors that hold bones close together in a synovial joint.

Articular Discs or Menisci

Fibrocartilage pad between articular surfaces of bones of some synovial joints.

Articular Fat Pads

At many synovial joints the synovial membrane includes accumulations of adipose tissue.

Outer Fibrous Membrane

Consists of dense irregular connective tissue that attaches to the periosteum of the articulating bones.

Articular Cartilage

Covers bones at a synovial joint. Also known as hyaline cartilage. It reduces friction between bones in the joint during movement and helps to absorb shock.

Double-Jointed

Does not mean a person has extra joints. It means the person has greater flexibility in their articular capsules and ligaments. And the joints are less structurally stable and more easily dislocated.

Synovial Fluid

Forms a thin film over the surfaces within the articular capsule. This viscous, clear or pale yellow fluid. Its several functions include reducing friction by lubricating the joint, and supplying nutrients to and removing metabolic wastes from the chondrocytes within articular cartilage.

Gomphosis

Or dentoalveolar joint, in which a cone-shaped peg fits into a socket. Ex. Roots of the teeth and their sockets. It permits no movement so it's classified as Synarthrosis.

Articulating Capsule composed of two layers:

Outer fibrous membrane and inner synovial membrane.

Articular (Joint) Capsule

Sleevelike, surrounds a synovial joint, encloses the synovial cavity and unites the articulating bones.

Synovial Joints

The bones forming the joint have a synovial cavity and are united by the dense irregular connective tissue of an articular capsule, and often by accessory ligaments.

Synovial Joint Cavity

The space between the articulating bones of a synovial joint, filled with synovial fluid. Also called a joint cavity. It allows a joint to be freely movable. All synovial joints are classified functionally as diarthroses.

Cartilaginous Joints

There is no joint cavity. The bones are held together by a bridge of cartilage

Fibrous Joints

There is no synovial cavity and the bones are held together by dense irregular connective tissue that is rich in collagen fibers

Accessory Ligaments

most synovial joints have these in addition to the ligaments formed by thickenings of the fibrous capsule.

The functional classification of joints

relates to the degree of movement they permit