478 The Knee-joint 



p. 482), and anterior tibial. The nerves are branches of the obturator, 

 anterior crural, internal popliteal (three), and external popliteal (two). 



Pains about the knee may be due to local troubles, such as 

 disease of the synovial membrane, the bones, the epiphyses, or the 

 bursae (p. 473). But it may be due to some distant cause, such as 

 disease of the spinal cord, or its membranes, or of the column (p. 210) ; 

 to pressure upon the trunk of the anterior crural, obturator, or sciatic 

 nerve ; or to reflex irritation, caused by disease of the sacro-iliac or 

 hip-joint. 



Bursae in the neighbourhood of knee-joint. There is a large 

 one between the patella and the skin, and a small one between the 

 tubercle of the tibia and the skin. Either of these may become in- 

 flamed by continued pressure, the disease constituting housemaid's 

 knee. When the bursal inflammation is acute, the surrounding parts 

 are swollen, red, and hot, and the case looks like one of joint-disease. 

 In the latter case the swelling is behind the patella and its ligament, 

 whilst in bursal inflammation the effusion is in front of them. If sup- 

 puration occur the abscess should be promptly opened, lest the pus 

 find its way into the articulation. (See illustration on p. 473.) 



A third bursa intervenes between the ligamentum patellae and the 

 upper part of the tubercle of the tibia. When acutely inflamed, this 

 bursa, bound down as it is, causes great pain, and bulges on either 

 side of the ligament. There is a bursa beneath each head of the 

 gastrocnemius ; that beneath the inner head often communicates with 

 the interior of the knee-joint, and also with another bursa which sepa- 

 rates the tendon of the semi-membranosus from the head of the tibia. 

 There are other bursaa between the internal lateral ligament and the 

 tendons of the sartorius, gracilis, and semitendinosus, and between the 

 external ligament and tendon of biceps. Lastly, there is the subcrureus 

 bursa, to which reference has already been made. 



The superior-tibio fibular membrane may communicate with that 

 of the knee-joint. 



The bursa under the inner head of the gastrocnemius and the in- 

 sertion of the semi-membranpsus is often full of fluid. When the knee 

 is extended the tendons are tightened and the tumour is made hard 

 and tense ; when it is flexed the outline of the tumour becomes less 

 definite. Sometimes fluctuation may be readily obtained between the 

 contents of this tumour and the over-abundant synovial fluid in the 

 joint. If the tumour be carelessly opened, septic inflammation spread- 

 ing from it may involve the knee-joint in acute disease. 



The relative position of structures around the knee. In front 

 the joint is almost subcutaneous. Behind are the popliteal vessels and 

 the internal popliteal nerve ; and on either side of them are the heads 

 of the gastrocnemius (the plantaris being with the outer), the semi- 

 tendinosus and membranosus, the biceps, and the external popliteal 

 nerve. Internally are the gracilis and sartorius, the internal saphenous 



