Joints and their classifications

what are joints? A joint is a place where two or more bones meet. There are several different types of joints, each producing different types and amounts of movement. Image © 2006 Jupiterimages Corporation

Joint Classification The structural classification of joints Fibrous joints (bones held together by dense collagen fibers) Cartilaginous joints (bones held together by cartilage) Synovial joints (bones held together by ligaments) The functional classification of joints Synarthrosis (an immovable joint) Amphiarthrosis (a slightly movable joint) Diarthrosis (a freely movable joint)

Different types of joint There are 3 different types of joint: 1. Immovable (or fixed) joints 2. Slightly movable joints Reference to skeletal structures could be enhanced by using a skeleton or skeletal models if available. Use this presentation to remind students of the names of a range of bones. Students must be confident in naming the bones of the skeleton and their position/ location in the body. Without this understanding they will struggle to identify the bones that form joints. 3. Movable (or synovial) joints

1. Fixed or immovable joints They are also called fibrous joints because the bones are held together by tough fibres. Immovable joints are found in the skull Fixed or immoveable joints such as those of the flat bones of the skull allow very slight movement – ask students why they should allow a little movement. Movement is necessary for expansion of the soft tissues of the brain and to absorb some of the force of impacts – if joints were completely fixed they might crack with an impact such as a blow on the head.

Fibrous Joints Sutures Occur only between bones of the skull Syndesmoses Interosseous membrane Between the tibia and fibula in the leg Gomphoses Articulations of the teeth with the sockets of the maxillae and mandible

2. Slightly movable joints Slightly movable joints are also called cartilaginous joints. The bones are separated by a cushion of cartilage. The bones can move a little bit, but ligaments stop them moving too far. bone cartilage bone Discuss with students the structure of the spinal column and why slightly moveable joints are the most suitable type of joint for the cervical, thoracic and lumbar spine areas. Ask them why the sacrum and coccyx areas of the spine are fixed joints? Answer: for attachment of lower back muscles (Sacrum) and balance (coccyx). ligaments

Cartilaginous Joints Two types of cartilaginous joints Synchondroses ( primary) Symphyses(secondary)

Cartilaginous Joints Synchondroses Connecting tissue is hyaline cartilage Epiphyseal (growth) plate Symphyses Slightly movable joint Ends of the articulating bones are covered with hyaline cartilage, but a disc of fibrocartilage connects the bones

3. Freely movable or synovial joints 90% of the joints in the body are synovial joints. They are freely movable. Synovial joints contain synovial cavity, synovial fluid which is secreted by the synovial membrane. This lubricates the joint. These are highly mobile joints, like the shoulder and knee. Synovial fluid Synovial joints offer a wide range of sporting movement. Synovial membrane Knee

Types of synovial joints In ball and socket joints, the rounded end of one bone fits inside a cup-shaped ending on another bone. Ball and socket joints allow movement in all directions and also rotation. The most mobile joints in the body are ball and socket joints. Examples: Shoulders and hips. Hip Describe ball and socket joints at the hip and shoulder. Discuss the movements possible at these joints. How do they help during sport?

Types of synovial joints Pivot joints have a ring of bone that fits over a bone protrusion, around which it can rotate. These joints only allow rotation. Atlas Example: The joint between the atlas and axis in the neck . Axis

Types of synovial joints In saddle joints, the ends of the two bones fit together in a special way, allowing flexion, extension,abduction,and adduction movements, but not rotation. Examples: The thumb is the only one. Hinge joints – as their name suggests – only allow flexion and extension movement. Examples: The knee and elbow. Elbow

Types of synovial joints Condyloid joints two concave surfaces of one bone fits into two convex surfaces of other bone . They allow flexion, extension,abduction,and adduction movements, but not rotation. Examples: between the metacarpals and phalanges in the hand. Gliding joints have two flat faces of bone that slide over one another. Examples: between the tarsals in the ankle.