TYPES OF JOINTS

Joints occur at regions where two bones meet. They are classified as

• Immovable joints: Also known as fixed joints.  There is relatively no movement between the bones. There is no cartilage between the joints. Examples: Bones of the cranium and facial bones that articulate with the teeth
• Movable joints: Also known as synovial joints. The bones of this joints are capable of movements. The bones are separated by cartilage called articular cartilage. The movement may be partial or freely moveable.
• Partially moveable joints: Very limited range of movement.            Example: The joint between the vertebrae; The joints of the cranium; The joints of the hip bones.
• Freely moveable joints: There are free movements between the articulating bones. The articular surfaces are covered with cartilage. This articular cartilage reduces the friction between the two surfaces of bones making the joint. It is covered by a synovial membrane which forms a closed sac. This sac contains a fluid called synovial fluid. The synovial fluid helps in lubricating the joint to reduce friction. 

Types of freely moveable joints 

Classification is based on the degree of movement that they allow. 

• Hinge joints: These joints allow the backward and forward movement in only one plane. Examples: Elbow and knee joints
• Ball and Socket joints: These joints allow movements in multiple planes. Examples: Shoulder and hip joints
• Pivot joints:  Only rotational movements are possible in these joints. Examples: The joint between the first and second cervical (neck) bones.