402 THE INFERIOR EXTREMITY 



ARTICULATIO GENU (KNEE JOINT). 



In the knee-joint three bones are in apposition, viz., 

 the distal end of the femur, the proximal end of the 

 tibia, and the patella. It is the largest and most com- 

 plicated articulation in the body ; and, when the bones are 

 examined in the dried skeleton, the joint presents an apparent 

 insecurity, because the bony surfaces show little adaptation 

 the one to the other. In reality, however, the knee joint is 

 very strong, and, on account of the strength of the ligaments 

 which retain the bones in place, it very rarely suffers dislocation. 

 The ligaments on the exterior of the joint are : 



1. The capsular ligament. 



2. Two collateral ligaments fibular and tibial. 



3. The ligamentum patellae (or anterior ligament). 



4. The oblique popliteal ligament. 



Dissection. Before the dissection of the knee joint itself is 

 commenced, the nerves which supply it, and the arteries which 

 anastomose around it and provide its blood supply should be 

 displayed and studied. To a certain extent they can be dissected 

 simultaneously. The superior, inferior, and middle articular 

 branches of the tibial nerve, the superior and inferior articular 

 branches of the common peroneal nerve, and the articular 

 branch of the obturator nerve were found during the dissection 

 of the popliteal fossa, each being accompanied by a genicular 

 branch of the popliteal artery. 



Note that the middle genicular branch of the tibial nerve, 

 the accompanying artery, and the articular branch of the ob- 

 turator nerve pierce the posterior ligament of the knee joint. 

 They supply structures inside the capsule, but the demonstra- 

 tion of their distribution is very difficult, and no attempt must 

 be made to follow them further at present. 



The branches of the femoral nerve to the vastus medialis, the 

 vastus intermedius, and the vastus lateralis send twigs to the 

 knee, and twigs of the descending branch of the lateral femoral 

 circumflex artery descend with the nerve to vastus lateralis to 

 take part in the anastomosis round the joint. The nerves and 

 the artery mentioned were found during the dissection of the 

 thigh. Attempt to trace them now to the knee, and demonstrate, 

 if possible, the anastomosis of the descending branch of the lateral 

 femoral circumflex artery with the superior lateral genicular 

 branch of the popliteal artery, and with the muscular branches 

 of the arteria genu suprema. Next trace the superior genicular 

 branches of the popliteal artery and the accompanying nerves. 

 The medial superior genicular artery, as it leaves the popliteal 

 fossa, pierces the posterior intermuscular septum of the thigh, 

 and then passes between the tendon of the adductor magnus 

 and the femur before it enters the vastus medialis, where it 

 anastomoses with the adjacent arteries. The lateral superior 

 genicular artery, and the accompanying nerve, must be followed 



