646 HUMAN ANATOMY. 



The quadriceps tendon is separated from the femur by a large bursa, which, ir 

 from 70 to 80 per cent, of cases, communicates with the knee-joint and may be in- 

 volved in its diseases. When separate from the joint and distended by effusion, it 

 may be mistaken for synovitis of the knee, but the patella will not be floated up and 

 the concavities at either side of that bone and those at the sides of the ligamentum 

 patellae will not be effaced. 



. The prepatellar bursa, separating the patella from the skin, is frequently enlarged 

 in persons who spend much time kneeling, — " housemaid's knee." 



The bursa between the ligamentum patellae and the tubercle of the tibia may be 

 enlarged or inflamed, and is then apt to be painful on account of its compression 

 between two non-distensible structures, the bone and the ligament. The little pad 

 of fat (page 400) between the tubercle and the ligament, which protrudes at the sides 

 of the latter when the quadriceps extensor is in action (page 405), should not be mis- 

 taken for enlargement of this bursa. 



Posteriorly — over the ham — the skin is thinner and less movable. The deep 

 fascia — here the popliteal fascia — is dense and exerts marked obstruction to the exten- 

 sion of abscess, growth, or aneurism towards 

 Fig. 616. thg surface, in this way causing severe pain 



from the pressure upon the nerves that run 

 through the space. As the latter is open 

 above and below, abscesses may extend in 

 -Vastus internus either direction. 



-Tendon of ' ^"^ ^^ iufcction may be guided to the 



lectus subfascial region in the ham from the pelvis 



or the buttock by the great sciatic nerve, or 



from the thigh by the femoral vessels, or 



Fractured surfaces from the leg by the short saphenous vein, 



° P^ ^ ^ or by the deeper vessels and the lymphatics. 



The relations of the fascia and muscles 



of the thigh to the patella and the knee- 



^ivom p™eiia^tTcaps°u'- joi^t and to their injuries and diseases have 



; n l^r^l'gament of knee- been sufficiently described (Figs. 424-430, 



C_ . / ^°'" P^S^^ 409-418). 



The hamstring tendons are not infre- 

 quently divided, as, for reasons already 

 Dissection of fracture of patella. given, ankylosis _of the knee-joint is usu- 



ally in the position of flexion (page 412). 

 They are made very tense when the pelvis is strongly flexed on the thigh, the knee 

 remaining extended. They may be ruptured if excessive force is applied under 

 these circumstances. 



The biceps tendon is easily felt on the outer side of the ham, with the peroneal 

 nerve, also readily palpable, lying against its inner and posterior border. At the inner 

 side of the ham the semitendinosus tendon is nearer the mid-line, nearer the surface, 

 more easily outlined, thinner, and more cord-like than the semimembranosus tendon, 

 which is the most deeply situated of the three hamstrings. The line for dividing 

 these tendons is preferably a little above the level of the knee-joint and about opposite 

 the most salient parts of the femoral condyles. 



In the popliteal region there are several bursae : (a) the largest is between the 

 inner head of the gastrocnemius and the semimembranosus and the inner condyle of 

 the femur, extending downward to the inner tibial tuberosity and even as low as the 

 upper margin of the popliteus ; it communicates with the joint in 50 per cent, or 

 more of cases (Foucher, Gruber) ; (d) a smaller bursa is found between the semi- 

 membranosus and the internal tuberosity of the tibia, communicating usually with 

 the above-described bursa. Externally there are : (c) a bursa between the lateral 

 ligament and the tendon of the popliteus ; (d) a. bursa — a diverticulum of the syno- 

 vial membrane of the knee (Nancrede) — between the same tendon and the external 

 tibial tuberosity ; (e) a bursa between the external lateral ligament and the biceps 

 tendon, in close relation to the external popliteal nerve ; and (/) a bursa between 

 the outer head of the gastrocnemius and the external condyle of the femur. 



