Synovial Joints: Definition, Meaning, Examples, Types, Diagram, Classification

What are Synovial Joints?

A synovial joint is one of the most paramount structural formations of the skeletal system. It plays a significant role in the elevation of movement and supports the body structure in various sections of the human structure. One of the major peculiarities is the shape of their design which allows people to move in different sections from other kinds of joints.

Structural Features of Synovial Joints

There are several key structural components of the synovial joint that are responsible for defining the functionality of the same:

Synovial Fluid

A viscous fluid fills the joint cavity lubricating the articulating surfaces and also reducing any friction inside the joint.

The Articular Capsule

It is a sheath that surrounds the joint and encloses the joint cavity, providing structural support to the joint.

Articular Cartilage

Its smooth, white tissue covers the articulating surface of the bones forming the joints. It provides frictionless, smooth motion, so the wear and tear are reduced.

Reinforcing Ligaments

Ligaments are dense bands of fibrous connective tissue that stabilize the joint and help guide the movements of the articulating bones.

Joint Cavity

A space that exists between the articulating bones in the digits, padded by the synovial fluid enabling the free, nonbinding movement of bones.

Types of Synovial Joints

Six major types of synovial joints are distinguished based on the shapes of their articulating surfaces and the movements they allow:

Plane (Gliding) Joints

Flat articulating surfaces that allow for sliding or gliding movements. Carpals of the wrist and tarsals of the ankle allow for movement and nonaxial playing.

Hinge Joints

Hinge joints have a hinge shape configuration, thus allowing for uniaxial movement either in flexion or extension, along one plane.

Elbow Joint

Interphalangeal joints of the fingers and toes.

Pivot Joints

The rounded end of a bone rests against another bone that has a ringlike structure, thereby allowing rotational movement along with the main axis.

A representative example is the proximal radioulnar joint, which allows the bones of the forearm, the radius, to cross over the ulna when rotating the hand from palm down to palm up positions.

Condyloid Joints

These are characterized by an oval-shaped convex surface fitting into a complementary concave surface. It permits biaxial movements (flexion-extension and abduction adduction). It is found in the wrist joints (radiocarpal) and knuckle joints (metacarpophalangeal).

Saddle Joints

This joint resembles a saddle shape with concave and convex surfaces that fit together. It allows for biaxial movements similar to condyloid joints. It is present at the carpometacarpal joint of the thumb; it allows the opposition of the thumb.

Ball and Socket Joints

Ball and socket joints have the ball in one bone and a socket in another. Ball and socket joints allow the largest range of motion of all synovial joints and also allow movement in multiple axes. Examples include the shoulder joint and hip joint.

Importance of Synovial Joints

Importance of synovial joints is:

• Enable free movement

• Essential for locomotion & manipulation

• Allow complex body actions

• Maintain flexibility and posture

Disorders of Synovial Joints

Synovial joints play an extremely crucial role in movement and general body functionality. However, these joints happen to be susceptible to many disorders, such as:

Osteoarthritis

• Degenerative joint disease of the articular cartilage.

Rheumatoid Arthritis

• Inflammatory disease that leads to joint destruction.

Sprains and Strains

• Injuries of the ligaments and tendons around a joint, leading to its stability and mobility being compromised.

Synovial Joints NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Classification of synovial joints

• Disorders of synovial joints

Practice Questions for NEET

Q1. Which of the following options correctly identifies the location of a pivot joint?

1. The hip and shoulder joint

2. Between the atlas and the odontoid process of the axis

3. Sternoclavicular joint

4. Temporomandibular joint

Correct answer: 2) Between the atlas and the odontoid process of the axis

Explanation:

A pivot joint is a type of synovial joint that allows rotational movement. It occurs specifically between the first (atlas) and second (axis) cervical vertebrae in the neck. The atlas is the topmost vertebra that connects to the skull while the axis lies just below the atlas. The odontoid process is a bony projection on the axis that acts as a pivot point. The pivot joint formed between the atlas and the odontoid process allows for the rotation of the head from side to side, as in shaking the head to indicate "no." This joint enables the important function of head rotation and is an example of a pivot joint in the human body.

Hence, the correct answer is option 2) Between the atlas and the odontoid process of the axis.

Q2. The pivot joint between the atlas and the axis is a type of:

1. Fibrous joint

2. Cartilaginous joint

3. Synovial joint

4. Saddle joint

Correct answer: 3) Synovial joint

Explanation:

The pivot joint connecting the atlas (C1) and axis (C2) vertebrae is a unique synovial joint, commonly referred to as the atlantoaxial pivot joint. It is essential for the head's rotational movement, such as when one nods in disagreement or affirmation. This joint's structure includes the odontoid process (dens) of the axis, which serves as the pivot, while the anterior arch of the atlas and the transverse ligament provide stability and keep the dens in position. The primary function of this joint is to allow the atlas to rotate around the dens, facilitating the head's rotation. It is a key component of the cervical spine, contributing significantly to neck flexibility and overall body coordination. It is crucial to recognize that pivot joints are designed for rotation around a single axis, and the atlantoaxial joint exemplifies this, playing a pivotal role in head and neck mobility.

Hence, the correct answer is option 3) Synovial joint.

Q3. The elbow joint is an example of:

1. Hinge joint

2. Gliding joint

3. Ball and socket joint

4. Pivot joint

Correct answer: 1) Hinge joint

Explanation:

One type of synovial joint, also referred to as a freely moving joint, is the hinge joint. The elbow and knee both have hinge joints. The pivot joint is located between the atlas and axis, the gliding joint is located between the carpals and the ball and socket joint is located between the shoulder and hips.

Hence, the correct answer is option 1) Hinge joint.

Also Read:

• MCQs on Types of Synovial Joints

• Fibrous Joints

• List of the 206 Bones in Our Body