Flexion of knee joint is caused by

KNEE JOINT:- Largest and most complex joint of the body.Fusion of 3 joints(lateral femorotibial, medial femorotibial, and femoropatellar) in one.Type: condylar synol joint. Movements:-Flexion,extension,medial and lateral rotation.Flexion and extension takes place in upper compament of the joint, above the menisci. They differ from ordinary hinge movements-The transverse axis around which these movements takes place is not fixed. During extension, the axis moves forward and upwards, and in the reverse direction during flexion.These are accompanied by rotation. Medial rotation of the femur occurs during the last 30 degrees of extension, and lateral rotation of the femur occurs during initial stages of flexion. When feet is on the ground, while standing erect, medial rotation of femur occurs during the last 30 degrees of extension as in " attention " by the vastus medialis.During the position of "stand at ease", there is lateral rotation of femur, during initial stages of flexion by the popliteus. Muscles involved:-1. Flexion- Biceps femoris Semitendinosus Semimembranosus 2. Extension-Quadriceps femoris. {Reference: BDC 6E pg no. 145}