A joint is the part of your body where two or more bones meet and are connected to each other. Depending on the type of the joint, the bones could be allowed to move freely, a little bit or not at all. Elbows and knees are two of the most complex joints in the human body.
Types of Joints
There are three main types of joints. These are fibrous, cartilaginous and synovial. Fibrous joints do not allow for any movement and are found on your spine at the point where it connects to the skull and the pelvis. Cartilaginous joints occur where bones are connected to each other via cartilage. This cartilage allows for a little more movement than fibrous joints. Your ribs are an example of cartilaginous joints. The final type of joint is synovial. These joints allow for the most movement. Synovial fluid contained in sacks at the joint lubricates the bones and allows them to twist and bend against each other. All of your moving parts, including your knees and elbows, are synovial joints.
Elbow and Knee Basics
Elbows and knees are not as simple as they may seem. Knees, for example, are the meeting and cooperative movement of four different bones. Knees are also one of the parts of the body that are most likely to be injured during accidents or strenuous activity. Elbow joints are made up of three bones, and while they are not as susceptible to injury as the knee, it is still wise to try and protect them from damage.
The knee is one type of synovial joint. It allows for a great deal of movement. More specifically, it is a hinge joint. This type of joint acts like a hinge on a door and allows for your leg to bend. The knee is the point where the femur meets the tibia and the fibula. The patella is a small bone that sits on top of this junction and glides along the bottom of the femur as your leg bends. This is also called a kneecap.
Like the knee, the elbow joint is a synovial joint classified as a hinge-type joint. It allows for you to extend your arm straight out or bend it inward. The elbow joint is the meeting of three bones: the humerus, the ulna and the radius. The humerus is your upper arm while the ulna and the radius make up your lower arm. The elbow contains more than just the hinge joint where the humerus and the ulna meet. A humeroulnar joint between the radius and humerus allows for the rotation of the hand. Finally, a pivot joint occurs where the radius meets the ulna and allows these two bones to twist slightly around each other.