A Joint is nothing but a junction between two or more bones or cartilages. It is a device to permit movements. In this post we shall talk in brief about the classification of joints.
There are more joints in a child than in an adult because as growth
proceeds some of the bones fuse together, Ex: infant mandible, ischium, pubis, etc.
CLASSIFICATION OF JOINTS
A. Structural Classification
- Fibrous joints
(a) Sutures
(b) Syndesmosis
(c) Gomphosis - Cartilaginous joints
(a) Primary cartilaginous joints or synchondrosis
(b) Secondary cartilaginous joints or symphysis - Synovial joints
(a) Ball-and-socket or spheroidal joints
(b) Sellar or saddle joints
(c) Condylar or bicondylar joints
(d) Ellipsoid joints
(e) Hinge joints
(f) Pivot or trochoid joints
(g) Plane joints
B. Functional Classification (according to the degree of mobility)
- Synarthrosis (immovable), like fibrous joints
- Amphiarthrosis (slightly movable), like cartilaginous joints
- Diarthrosis (freely movable), like synovial joints
C. Regional Classification
- Skull type: immovable.
- Vertebral type: slightly movable.
- Limb type: freely movable.
D. According to number of articulating bones
Now lets see each heading in the Classification of Joints in brief.
FIBROUS JOINTS
The bones are joined by fibrous tissue in fibrous joints. They can be immovable or slightly moveable.
Sutures: These are only found in skull, and are immovable. According to the shape of bony margins, the sutures can be:
(i) Denticulate, Ex: lambdoid suture
(ii) Plane, Ex: internasal suture
(iii) Serrate, Ex: interparietal suture
(iv) Squamous, Ex: temporo-parietal suture
(v) Schindylesis type, Ex: rostrum of sphenoid & upper border of vomer.
Syndesmosis: Connected by the interosseous ligament. Ex: inferior tibiofibular joint
Gomphosis: Peg and Socket Joint. Ex: root of the tooth in its bony socket
CARTILAGINOUS JOINTS
The bones are joined by cartilage in Cartilaginous Joints.
Primary cartilaginous joints: Bone are held together by plate of hyaline cartilage so the joint is immovable and strong. Ex: Costochondral joints
Secondary cartilaginous joints: Bone are helpd together by a thin layer of hyaline cartilage, and united by a disc of fibrocartilage. Ex: Symphysis pubis
SYNOVIAL JOINTS
Ball-and-Socket (Spheroidal) Joints: A globular head (male surface) fits into a cup-shaped socket (female surface). Movements can occur many axes which have one common centre. Ex: Shoulder Joint
Saddle (Sellar) Joints: Articulating surfaces are concavoconvex. Movements are similar to those permitted by an ellipsoid joint, with some rotation around a third axis which, cannot occur independently. Ex: Femur and Patella
Condylar (Bicondylar) Joints: Two distinct condyles (convex male surfaces) fitting into reciprocally concave female surfaces. Ex: Knee joint
Ellipsoid Joints: Articular surfaces include an oval, convex, male surface fitting into an elliptical, concave female surface. Ex: Wrist Joint
Hinge Joints (Ginglymi): Articular surfaces are pulley-shaped. Ex: Ankle joint
Pivot (Trochoid) Joints: Articular surfaces comprise a central bony pivot (peg) surrounded by an osteoligamentous ring. Ex: Median atlanto-axial joint
Plane Synovial Joints: Articular surfaces are more or less flat (plane). They permit gliding movements (translations) in various directions. Ex: Intercarpal joints
Synarthrosis
Fixed joints at which has no movement. The articular surfaces are joined by tough fibrous tissue. Often the edges of the bones are dovetailed into one another as in the sutures of the skull.
Amphiarthroses
Joints at which slight movement is possible. A pad of cartilage lies between the bone surfaces, and there are fibrous ligaments to hold the bones and cartilage in place. Ex: intervertebral discs
Diarthroses or synovial joints
Freely movable joints, though at some of them the movement is restricted by the shape of the articulating surfaces and by the ligaments which hold the bones together.
Simple joint:
When two bones articulate, Ex: interphalangeal joints
Compound joint:
More than two bones articulate within one capsule, Ex: elbow joint, wrist joint
Complex joint:
When joint cavity is divided by an intra-articular disc, Ex: temporomandibular joint
Last updated on April 15th, 2020 at 12:50
