A joint is a point where two or more bones meet. The three main types of joints are fibrous, cartilaginous, and synovial.
Fibrous Joints
Fibrous or ‘synarthrodial’ joints are fixed or immoveable joints. Ligaments hold the bones together. They have no or virtually no movement, for example, teeth in their bony sockets, the radioulnar joint in the elbow, and tibiofibular joints at the knee and ankle.
Cartilaginous joints
Cartilaginous joints occur where the connection between the articulating bones is made of cartilage. For example, between vertebrae in the spine and pubis symphysis in the pelvis. Other names for cartilaginous joints are synchondroses and symphyses.
Synchondroses are temporary joints, only present in children until the end of puberty. For example, the epiphyseal plates in long bones.
Symphysis joints are permanent cartilaginous joints, for example, the pubic symphysis.
Synovial Joints
- Synovial (diarthrosis): Synovial joints are by far the most common classification of a joint within the human body.
- They are highly moveable and all have a synovial capsule (collagenous structure) surrounding the entire joint, a synovial membrane (the inner layer of the capsule) that secretes synovial fluid (a lubricating liquid), and cartilage is known as hyaline cartilage which pads the ends of the articulating bones.
- There are 6 types of synovial joints which are classified by the shape of the joint and the movement available.
Types of Synovial Joint
Hinge joint
- Movement – Flexion/Extension
- Examples – Elbow/Knee
Pivot joint
- Movement – Rotation of one bone around another
- Examples – Top of the neck (atlas and axis bones)
Ball & Socket
- Movement – Flexion/Extension/Adduction/Abduction/Internal rotation/External Rotation
- Examples – Shoulder/Hip
Saddle
- Movements – Flexion/Extension/Adduction/Abduction/Circumduction
- Example – CMC joint at the base of the thumb
Condyloid
- Movements – Flexion/Extension/Adduction/Abduction/Circumduction
- Examples – Wrist/MCP in the hand & MTP joints in the foot.
Gliding
- Gliding movements
- Intercarpal joints in the hands
