Temporary joint between the epiphysis and diaphysis of a long bone formed by cartilage of epiphyseal plate
Symphysis (bones joint by fibro-cartilage)
Eg: attachment of the right and left pubic bones by the cartilaginous interpubic disc called the pubic symphysis.
Joints whereby two bones are separated by a film of slippery synovial fluid.
Are the most structurally complex of all joints. The bones are separated by a space called the joint cavity that contains synovial fluid. The fluid is a lubricant that nourishes the joint cartilages and removes their wastes and contains phagocytes that clean up tissue debris resulting from cartilage wear and tear. The adjoining bones are each covered with articular cartilage (hyaline). A joint capsule encloses the cavity which contains the synovial fluid and this is made up of two structures; The inner synovial membrane and the outer fibrous capsule.
Accessory structures of s synovial joint include tendons, ligaments and bursae. A tendon is a strip of tough collagenous connective tissue that attaches muscle to bone. A ligament attaches one bone to another. A bursa refers to a fibrous sac that is filled with synovial fluid and located either between adjacent muscles or where a tendon passes over a bone to help cushion muscle and reduce friction between a tendon and bone.
A synovial joint is the body’s most moveable joint where the movements are almost friction-free.
Eg: Jaw, elbow, interphalangeal, hip and knee joints.
Understand and explain the trade-off between mobility and stability of a joint.
Whilst it is important for a joint to bear heavy loads and withstand compression while executing smooth and precise movement, it is equally important for the joint to be able to ensure stability of the joint and possess a mechanism that limits its range of motion. The type of joint along with the surrounding structures, are the key factors which contribute to the stability of the joint.
The factors responsible for stability include:
The joint type (if ball and socket type, is the socket quite deep or shallow). Each type is distinguished by the shape of their articular surface and their specific structure that allows for precise degree/s of freedom.
Ligaments which help to ensure stability at a joint by way of their strength and tautness exerted during a movement to limit the range of motion. Eg. Shoulder capsule and ligaments, cruciate ligaments of the knee
Muscles and tendons limit movement at a joint by adopting a state of tension called muscle tone to restrict movement. This is the first line of defense against dislocations that is for instance in the preventing shoulder dislocation by the tension in the biceps brachii muscle.
We could remove some ligaments from the collateral ligaments of the knee and it would certainly be able to function with increased mobility. However, it would constantly dislocate and this is why we have a tradeoff between mobility and stability.