Write a note on Joints. Explain the Classification of joints?

 JOINTS:

Joints are defined as, When two or more bones or cartilages come in contact with each other an articulation or joint is formed.

The study of joints is known as Arthrology.

Classification Of Joints:

The joints are classified into following:

1. Fibrous joints
2. Cartilaginous Joints
3. Synovial Joints

1. Fibrous Joints: 

They are fixed, immoveable joints. In Fibrous joints, the union is due to dense fibrous tissue and mainly limited to the skull. They are furthur divided into three major groups:

• Sutures
• Gombhosis
• Syndesmosis

Sutures: These are the joints of skull bones. They are immoveable and fixed. These are the sites of active bone growth. There are following types of sutures:

• Serrate Sutures ( Saw-like, Sagittal sutures between two parietal bone)
• Denticulate Sutures ( Tooth-like, lambdoid suture between parietal and occipital bone)
• Squamous Sutures( Overlap bones, Temporo-parietal suture )
• Limbous Sutures( Serrated or ridged,  Temporo-parietal suture)
• Plane Suture( Zygomatico-palatine suture)

https://www.shutterstock.com/image-photo/suture-between-skull-bones-228474442

Gombhosis:  Peg and socket joint

It is a specialized joint in which the teeth fit in to their sockets situated in the maxilla and mandible. The ligament which connects the tooth with the socket or alveolus called periodontal ligament.

Syndesmosis: It is a type of fibrous joint in which the two bones are united with each other by interosseous ligament. For example, Inferior tibio-fibular joint, Coracoclavicular joint.

2. Cartilaginous Joints:

These are slightly moveable joints, In these joints, the bones are united by a cartilage. They are subdivided into two major groups:

1. Primary Cartilaginous joints             2. Secondary Cartilaginous joints

Primary cartilaginous joints: They are also known as Synchondroses.

• These are the joints seen mainly in developing appendicular bones.
• They are completely immoveable.
• These joints are temporary, because at the age of 18 -20 years the epiphyseal cartilage is ossified.
• For Example; Joints between the ends and shaft of growing long bones.

Secondary Cartilaginous Joints: ( Symphyses )

• These joints are seen in Axial bones.
• These joints are permanent.
• They are slightly moveable and mobility depends on white-fibro cartilage.
• For Example: Public symphysis, Joints between the bodies of vertebrae.

3. Synovial Joints:

They are moveable joints, also known as Diarthrosis, At these joints, the articulating bone surfaces are covered with articular cartilage, an articular capsule surrounds the joint.

These are many types of synovial joints:

• Gliding: In it, the articulating bone surfaces are nearly flat. Such as, intermetatarsal, intercarpal joints.
• Hinge Joint; In it, One articulating bone surface is convex and the other is concave. For example, Ulnohumeral joints.
• Pivot joints: In it, Rotation is permitted around one axis. For example, Atlantoaxial joints.
• Condyloid Joints: One articulating bone surface is an ovular convex shape , and the other is reciprocally shaped concave surface.  For example, Radiocarpal joints.
• Ball and Socket joint: In these joints, Rotation is permitted in all directions. Examples include: Hip and shoulder joints.

Explanation: Synovial joints vary widely in structure and movement capabilities. Two synovial structures are associated with synovial joints are Bursae and tendon sheaths. 

Bursae are small capsules, lined with synovial membranes and filled with synovial fluid. 

Tendon sheaths are double-layered synovial structures that surrounds tendons associated with bones.

References: 

General Anatomy by Dr. Ghulam Ahmad.

Basic Biomechanics By Susan J. Hall.

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About Author;

Tayyba Saleem ( PT )

Doctor Of Physical Therapy.