Knee Joint Anatomy Medical

KNEE JOINT ANATOMY
Knee Joint Anatomy medical legal images

The knee contains two joints, the tibio-femoral joint and the patello-femoral joint. The tibio-femoral joint, is between the tibia or shin bone, and the femur or thigh bone.

It is stabilized by the two collateral ligaments, the two cruciate ligaments, the two menisci and the muscles around the knee. Knee Joint Anatomy medical legal images.

The patello-femoral joint is between the patellar or knee cap, and the femur. It is stabilized by the medial retinaculum, the vastus medialis oblique muscle, the patella tendon and the quadriceps tendon.

The joint capsule surrounds the knee joints, keeping the synovial fluid in, and blood and adjacent tissues out. Knee Joint Anatomy medical legal images.

The articulating surfaces at the ends of the tibia and the femur, and the inner surface of the patella, are covered by a smooth articular cartilage. The inner layer of the joint capsule has a thin synovial membrane that secretes synovial fluid into the knee joints to provide lubrication and nutrition.

The smooth articular cartilage and the oily synovial fluid produces a durable, low friction surface that helps to distrIbute forces when the bones move against each other during knee flexion, extension and rotation. Knee Joint Anatomy medical legal images.

The knee is the intermediate joint of the lower limb. It is mainly a joint with one degree of freedom which allows the end of the limb to be moved towards or away from its root or, in other words, allows the distance between the trunk and the ground to be varied. The knee has an accessory or second degree of freedom, rotation of the long axis of the leg, which only occurs when the knee is flexed.

From the mechanical point of view, the knee is a compromise which sets to reconcile two mutually exclusive requirements:
to have great stability in complete extension, when the knee is subjected to severe stresses resulting from the body weight and the length of the lever arms involved:
to have great mobility after a certain measure of flexion has been achieved. This mobility is essential for running and the optimal orientation of the foot relative to the irregularities of the ground.

The knee resolves this problem by highly ingenious mechanical devices but the poor degree of interlocking of the surfaces, essential for great mobility, renders it liable to sprains and dislocations.

The first degree of freedom is related to the transverse axis, around which occur movements of flexion and extension in a sagittal plane. This axis, lying in the frontal plane, runs through the femoral condyles horizontally. Because the femoral neck overhangs the femoral shaft, the axis of the femoral shaft does not coincide with that of the leg but forms with the later an obtuse angle of 170 to 175 degrees opening outwards. This is the physiological valgus of the knee. On the other hand, the centres of the three lower limb joints, the hip, knee and ankle, lie on a straight line which is the mechanical axis of the lower limb. In the leg it coincides with that of the leg itself but in the thigh it forms an acute angle of 6 degrees with the axis of the femur.

Bacause the hips are wider apart than the ankles, the mechanical axis of the lower limb runs obliquely inferiorly and medially and forms an angle of three degrees with the vertical. This angle is greater the wider the pelvis, as in the case of women. This also explains why the physiological valgus of the knee is more marked in women than in men.

The axis of flexion and extension is horizontal and the angle between it and the femoral axis is 81 degrees, and the angle between it and the leg is 93 degrees. Therefore during full flexion the axis of the leg does not come to rest immediately posterior to that of the femur, but posterior and slightly medial to it so that the heel moves medially towards the plane of symmetry of the body. Full flexion brings the heel into contact with the buttock at the level of the ischial tuberosity.

In addition to these sex-linked physiological variations, ...

1. By: Medilaw.TV
2. Categories Science & Tech
3. Views 101
4. Added :27-Dec-11
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