Our bones are connected by joints. Joints let us move, bend, and stay stable. They can be sorted into different types based on how they are built and how they work.

I. Different Types of Joints Based on Structure

1. Fibrous Joints

   • What They Are: Joints joined by strong tissue.
   • Types:
     • Suture Joints: These joints don't move at all. They are found between the bones in our skull (like the seam on a cap).
       • Fun Fact: Adults have 22 bones in their skull that connect with sutures.
     • Syndesmoses: These joints allow a little movement and are held together by tough bands (like the joint between lower leg bones).
     • Gomphoses: These are peg and socket joints (like where our teeth sit in our gums).

2. Cartilaginous Joints

   • What They Are: Joints where bones are joined by cartilage, which is a strong, flexible tissue.
   • Types:
     • Synchondroses: These joints are connected by a smooth type of cartilage (like the growth plates in long bones).
       • Fun Fact: During childhood, about 80% of a long bone's growth happens at these joints.
     • Symphyses: These joints are connected by tougher cartilage and allow a little movement (like the joint in our pelvis).

3. Synovial Joints

   • What They Are: These are the most common joints and are very movable.
   • Features:
     • Articular Cavity: This space has a special fluid to help our joints move smoothly.
     • Articular Cartilage: This covers the ends of the bones, making it easier for them to slide against each other.
     • Joint Capsule & Ligaments: These hold everything together and keep the joint stable.
   • Types:
     • Hinge Joints: These move in one direction (like our elbow and knee).
     • Ball-and-Socket Joints: These can move around in many directions (like our shoulder and hip).
     • Pivot Joints: These allow one bone to rotate around another (like the joint in our neck).
     • Condyloid Joints: These let us bend and extend without rotation (like our wrist).
     • Saddle Joints: These can move in two directions (like our thumb).
     • Plane Joints: These allow bones to slide over each other (like in our wrists).

II. Different Types of Joints Based on Function

Joints can also be classified by how much they can move:

1. Synarthroses (Immovable Joints)

   • Function: These joints don't move at all, providing support.
   • Examples: The sutures in the skull.

2. Amphiarthroses (Slightly Movable Joints)

   • Function: These give a little bit of flexibility and support.
   • Examples: The discs between our spine bones and the pubic symphysis.

3. Diarthroses (Freely Movable Joints)

   • Function: These joints can move a lot, giving us a wide range of motion.
   • Examples: All synovial joints, like the knee and shoulder.

III. Why Joints Matter in Our Bodies

• Number of Joints: Most adults have about 230 to 360 joints, depending on different factors.
• Movement: Joints help us walk, run, grab things, and more. They play a big part in how we live our lives.
• Support: Joints like the knee help support our body weight when we stand.

Conclusion

Knowing about the different types of joints and what they do helps us understand how amazing our bones and body are. Joints give us the ability to move and do our daily activities, balancing movement and support in our bodies.