THE KNEE-JOINT. 263 



The lower epiphysis of the femur presents an ossified 

 nodule at the ninth month of foetal life, a fact of con- 

 siderable value medico-legally in determining the age 

 of the child. The entire epiphysis, however, does not 

 unite with the shaft until the twentieth year ; the upper 

 epiphysis of the tibia at the twenty -fifth year. 



Movements of the Knee-joint. Flexion is performed by 

 the biceps, semi-tendinosus, membranosus, popliteus, and 

 accessorily by the gastrocnemius. Extension by the 

 quadriceps extensor, and tensor vaginae femoris. When 

 the leg is semiflexed, the joint can be internally rotated 

 by the sartorius, semi-tendinosus, and gracilis; externally 

 by the biceps. 



Relations of the Knee-joint, externally. The tendon of 

 the biceps and the strong process of fascia lata into which 

 is inserted the tensor fascia? ; internally and a little pos- 

 teriorly, the sartorius, semi-tendinosus, gracilis, and semi- 

 mem branosus ; all these tendons are inclosed in bursal 

 sheaths ; posteriorly, the tendon of the popliteus and the 

 tendon of the muscles forming the popliteal space, with 

 the contents of the space itself. 



Fracture of the patella when due to muscular action is 

 always transverse, and the separation of the fragments 

 to the upward traction of the quadriceps extensor acting 

 on the upper one, whilst the lower is retained in position 

 by the ligamentum patellae. With a view to treatment, 

 the tension should be relaxed, by extending the leg on 

 the femur, and by slightly flexing the thigh on the pel- 

 vis so as to relax the rectus muscle. Non-union is some- 

 times owing to the bulging of the synovial membrane 

 between the opposed fragments. 



The articulation between the upper extremities of the 

 tibia and fibula is an arthrodial joint, consisting of two 



