Skeletal system - WJECJoints

A joint is a place where two or more bones meet and is also called an articulation.

The role of joints and connective tissue

• Connective tissues consist of ligaments, cartilage and tendons.
• A joint is held together by ligaments which give the joints their stability.
• Cartilage is found at the ends of bones and where joints meet.
• Tendons attach muscles to the skeleton.

Synovial joints

Synovial joints (freely movable joints) allow us the free movement to perform skills and techniques during physical activity.

Synovial joints have synovial fluid in the joint cavity that lubricates or 'oils' the joint so it moves smoothly. Synovial fluid is made by the synovial membrane.

In synovial joints, the ends of the bones are covered with cartilage (called articular cartilage) which cushions the joint and prevents friction and wear and tear between the bone ends. Cartilage is a soft, spongy connective tissue. The articular capsule prevents wear and tear on the bones.

The bones in a synovial joint are connected by ligaments.

• Ligaments are a type of connective tissue and are tough, fibrous and slightly elastic.
• They connect bone to bone and help keep the joint together.
• They stabilise the joints during movement and prevent dislocation by restricting actions outside the normal joint range.
• They can absorb shock because of their elasticity, which protects the joint.
• They help maintain correct posture and movement.

The movement at a synovial joint is caused by the muscles attached across the joint. Muscles are attached to bone by tendons. Tendons are very strong, inelastic connective tissues that allow a muscle to pull on a bone to move it.

Types of synovial joints

Different types of synovial joints allow varying degrees of movement. These include:

1. Hinge - these can be found in the elbow, knee and ankle. Hinge joints are like the hinges on a door, and allow you to move the elbow and knee in only one direction. They allow flexion and extension of a joint.
2. Ball and socket - these types of joint can be found at the shoulder and hip and allow movement in almost every direction. A ball and socket joint is made up of a round end of one bone that fits into a small cup-like area of another bone.
3. Pivot - this joint can be found in the neck between the top two vertebrae. It allows only rotational movement such as moving your head from side to side as if you were saying 'no'.