martes, 10 de mayo de 2011

Joints and How they move

A joint is a point at which two or more bones meet. There are three types of joints in the body:
Fixed joints is a joint between two bones that doesnt move . Many of the joints in your skull are fixed joints. The skull plates don't move together or against each other, but they are connected or fused
Partly movable joints allow only a little movement..Your backbone has partly movable joints between the vertebrae. They are connected to each other by pads of cartilageand ligaments. They can only move a small amount
Movable joints allow movement and provide mechanical support for the body. Movable joints are the most common type of joint in your body. Your fingers, toes, hips, elbows, and knees all have movable joints. The surfaces of bones at movable joints are covered with a smooth layer of cartilage. The space between the bones in a movable joint is filled with a liquid called synovial fluid. The fluid lubricates and cushions the bones when they move at the joint. Ligaments help provide their stability and muscles contract to produce movement.
The knee joint is the largest joint in the body, consisting of 4 bones- the femur (thigh bone), the tibia (shin bone), fibula (outer shin bone) and patella (kneecap)- and an extensive network of ligaments and muscles..
There is a joint capsule that is a thick ligamentous structure that surrounds the entire knee. Inside this capsule is a specialized membrane known as the synovial membrane which provides nourishment to all the surrounding structures. The capsule itself is strengthened by the surrounding ligaments.
The stability of the knee owes greatly to the presence of its ligaments. Each has a particular function in helping to maintain optimal knee stability in a variety of different positions. There are two Collateral Ligaments ( inner and outer side) and two Cruciate ligaments.
Each knee joint has two crescent-shaped cartilage menisci. These lie on the medial (inner) and lateral (outer) edges of the upper surface of the tibia bone. They are essential components, acting as shock absorbers for the knee as well as allowing for correct weight distribution between the tibia and the femur.

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