It is one of the most resistant joints in the human body . On the one hand, it is sufficiently mobile to allow movement of the lower leg; indispensable function in order to carry out many daily activities , such as walking, sitting, maintaining an upright position and running. On the other hand, it is strong enough to take on the whole body weight .
What is the knee?
It is an articulation that consists of the meeting of three bones : femur, tibia and patella . The former are connected to each other by means of their ends, while the patella is located in front of the femur. The bone surfaces are covered with a thin layer of cartilage which protects them and which – making them particularly smooth – avoids dangerous friction during the movement phase.
Between the femur and the tibia there is also another fibrocartilaginous structure – the meniscus – which absorbs shocks , preventing contact between the bones during intense physical activities, such as running and jumping. The bones of the knee are finally surrounded by a capsule wrapped in the membrane which is responsible for producing the synovial fluid , which determines the lubrication of the joint .
The capsule is in direct connection with the ligaments that keep the knee in position, strengthen its structure and allow correct positioning of the bones. The patella is held in place by the patellar ligament , which extends from its lower edge to the tibia. On the other hand, the oblique and arched popliteal ligaments connect the femur to the tibia and fibula . Finally, the medial and lateral collateral ligaments connect the femur and the tibia, preventing the knee from moving sideways towards the inside or outside of the body, while the crusaders inhibit the excessive extension of the knee ( anterior cruciate) and do not allow the tibia to move posteriorly to the femur ( posterior cruciate ).
A series of other structures protects the joint from external forces and friction , specifically small bags containing lubricating liquid ( bags ) and adipose tissue formations that help, respectively, to reduce the friction between the bones and to function as a bearing capable of absorb external forces.
What is the knee for?
It allows flexion and extension of the lower leg relative to the thigh. Its range of movement is limited by its own anatomy and stops at about 120 ° but, compared to other similar joints, when it is moderately flexed it allows a certain freedom of rotation both inwards and outwards.