The Region of the Knee Joint. 353 



of the humerus ; whereas, in the knee joint, the axis, on 

 which the tibia moves, shifts its position, so that, in ex- 

 tension, the anterior part of the articular surface of the 

 tibia is in contact with the femoral condyles, while, in ex- 

 treme flexion, the posterior portions are in contact. This 

 is brought about by means of the gliding of one bone un- 

 der the other. If the termination of the movement of 

 extension be closely watched, it will be seen, that just be- 

 fore its completion, the leg and foot are suddenly turned 

 or rotated outward, and, on the commencement of the 

 movement of flexion, the leg and foot move primarily in- 

 wards, before flexion is well started. These movements 

 of eversion and inversion are caused by the direction of the 

 anterior articular surface of the internal condyle, which is 

 inclined obliquely outwards. In addition to the above, 

 there are two movements, that might be termed, pro-nation 

 and supinaition, and that can occur in the semi-flexed posi- 

 tion only, since, in this position, the ligaments are relaxed. 

 These movements take place between the tibia, be- 

 low, and the interarticular nbro-cartilages, above 

 the axis being vertical and passing through the 

 spine of the tibia whereas, the movements of flex- 

 ion and extension, as well as that of rotation, spoken of 

 above, as occurring at the end of extension and the begin- 

 ning of flexion, take place between the femur, above, and 

 the interarticular fibro-cartilages, below. In extension, all 

 the ligaments of the joint are on the stretch, with the ex- 

 ception of the ligamentum patellae and the anterior portion 

 of the capsular, whereas, in ordinary flexion, all are re- 

 laxed, excepting the patellar ligament and the front of the 

 capsule. The crucial ligaments strongly bind together 

 the femur and the tibia; the anterior preventing over- 

 extension, and the posterior over-flexion, and, in addition, 

 both assist the lateral ligaments in preventing any lateral 

 bending at the joint. 



