Joints

Joints aka articular surface can be defined as a point where two or more bones are connected in a human skeletal system. Cartilage is a type of tissue which keeps two adjacent bones to come in contact (or articulate) with each other. 3 Types of joints are Synovial Joints, Fibrous Joints, and Cartilaginous Joints. Joints help in bringing about movements in different parts of the body. Let us see the classification of joints and anatomy of different types of joints.

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Classification of Joints

Joints can be classified in different ways depending on:

1. The amount of mobility permitted by the joints
2. Type of tissue connecting the bones

Each of these types can be further subdivided. Let’s look at each classification individually.

A] The amount of mobility permitted by the joint

(Source: TeachPE.com)

Depending on the degree of mobility permitted by the joint, we can classify them as:

• Fixed Joint or Synarthroses– The word ‘syn-‘ tells us that the bones are fused and therefore permit minimal or no movement. These joints are fibrous joints which means that the binding tissue between two bones is ‘fibrous’ in nature. Example of a fixed joint is the sutures between skull bones.
• Slightly Movable Joint or Amphiarthroses– This joint permits slight mobility that is more than what is seen in a fixed joint. The binding tissue in this type of joint is cartilaginous in nature. Example of a slightly moveable joint is those found between intervertebral discs.
• Freely Moveable Joint or Synovial Joints– These joints permit maximum movement between the bones involved. They are also called as ‘diarthroses’ and are further classified into 6 types depending on the kind of movements possible.

Types of Synovial Joints

(Source: opencurriculum.org)

• Ball and socket joint– This kind of joint involves two bones. One of the bone has a large rounded end which fits into a cup-like socket of the other bone. This kind of joint is generally found in large bones such as the shoulder joint and hip joint. A ball and socket joint provides the greatest degree of movement among different kinds of joints including rotation, flexion, extension, abduction, and adduction.
• Hinge joint-This joint is said to be a very simple joint that allows movement only in one axis. It allows only two kinds of movements- flexion and extension. Example of this joint is the joints found between in the elbow and knee.
• Pivot joint– This type of joint allows rotation along one axis only. A common example of this type of joint is the atlantooccipital joint in the neck.
• Ellipsoid/gliding joint– This joint is very similar to the ball and socket joint but without rotation. It allows movements only in two axes. Example of this is the wrist joint.
• Saddle joint– It is similar to an ellipsoid joint which involves two bones- one of the bones has a convex surface while the other has a concave surface. The convex surface of one bone articulates with the concave of the other to allow limited rotational movement. A very classic example of this kind of a joint is the carpo-metacarpal joint in the thumb.

B] Type of Tissue Connecting the Bones

Based on the type of tissue connecting the bones, we can classify joints as:

• Fibrous– The tissue connecting the two bones is fibrous in nature
• Cartilaginous– Cartilage forms the connecting tissue between two or more bones
• Synovial– The two bones form a synovial cavity with synovial fluid which forms the connecting tissue

Apart from movement and locomotion, joints also help stabilize the different parts of the body.

You can download Locomotion and Movement Cheat Sheet by clicking on the download button below

Solved Example for You

Q: What kind of a joint is in the wrist?

1. Saddle Joint
2. Pivot Joint
3. Gliding Joint
4. Ball and Socket Joint

Sol: The correct answer is  (c) Gliding Joint

This joint allows movement only in two axes and is found in the wrist joint between the radius, scaphoid and lunate bones.

FAQ’s for You

Q1. Describe the various kinds of skeletal joints in human body according to their mobility, giving one example for each.

Answer:  On the basis of mobility, joints are classified into three main groups:
1. Fibrous joint: These do not allow any movement because the bones are firmly fixed together by strong collagen fibres. Example: skull and tooth joint.
2. Cartilaginous joint: The two bones are joined together with the help of a disc or pad of white fibrous cartilage. Example: sternum, ribs, vertebral column, etc.
3. Synovial joint: These are freely movable joints which allow movement in one or more directions. The bones are covered by a membrane called synovial membrane and cavity is filled with synovial fluid.

These are further of various types:

A. Ball and socket joint in the shoulder and hip joint.
B. Hinge joint in elbow and knee joint.
C. Pivot joint in radius and ulna below the elbow.
D. Gliding joint in wrist and tassels.
E. Saddle joint in carpels and metacarpals of a human thumb.
F. The condyloid joint in fingers.

Q2. Fixed joints are also called as?

Answer: Synarthrosis joint or fixed joint or immovable joint – these joints do not allow any movement because the bones are firmly fixed together by strong fibres. These joints in the skull are called sutures. The attachment of tooth with socket in jaw is example.
B. Amphiarthroses joint or slightly movable joint or cartilaginous joint or imperfect joint – these joints, the two bones are joined together with the help of a disc or pad of white fibrous cartilage. The disc of cartilage restricts the movement in these joints due to which these joints show limited or slight movement. The movement in these joints are only possible because of compression of the pads of cartilage present on the articulated or ends of the bone taking part in the joints. Examples are in sternum-ribs, pubic symphysis.
C. Diarthrosis joint or synovial joint or free movable joint – these are freely movable joint which allow movement in one or more directions. Examples are shoulder joint, hip joint, elbow joint.
So, the correct answer is ‘Synarthrosis joint’.

Q3. The joint which helps in movement in all directions is called as?

Answer: Ball and socket joints are found at the shoulder and the hip. They are able to move in all directions or in all three dimensions. Hinge joints are found at the elbow and knee and they only allow movement in one direction or in only one plane. Hinge joints are formed between two or more bones where the bones can only move along one axis to flex or extend. A pivot joint (trochoid joint, rotary joint, lateral ginglymus) is a type of synovial joint. In pivot joints, the axis of a convex articular surface is parallel to the longitudinal axis of the bone. Pivot and hinge joints can be both considered cylindrical joints. These joints are also called “fixed” or “immovable” joints, because they do not move. These joints have no joint cavity and are connected via fibrous connective tissue. The skull bones are connected by fibrous joints. Sutures are found between bones of the skull.

Q4. Name the type of joint between between phalanges.

Answer: Hinge joint is the type of joint present between the phalanges. Hinge joint is a type of synovial joint. The articular surfaces of this joint are moulded in such a way that the movement takes place only in one plane. So the fingers are able to move one to one side ie flexed as they have hinge joint.