1184 



SURGICAL AND TOPOGRAPHICAL ANATOMY 



Dislocation of the patella. — The followinfi^ anatomical facts account for this 

 taking jjlace much more frequently outwards: — (1) The inner edge of tlie jjatella 

 is more prominent, and thus more exposed to injury; it is also well supi)orted, as 

 is seen when, the parts ))eing relaxed, the fingers are insinuated beneath each 

 border. (2) The pull of the extensor uj^on the patella, ligamentu.m patellse, and 

 tibia is somewhat outwards, as the tibia is directed a little outwards to the femur, 

 to meet the inward direction of this bone; the femora being directed inwards here, 

 to bring the knee-joints nearer the centre of gravity, and, so, counterbalance their 

 wide separation above at the pelvis. The outward pull of the quadriceps upon the 

 patella is, in all normal action of the muscle, counteracted by the space taken in 

 the trochlear surface by the external condyle, this being wider and creeping uj) 

 higher, and having a more prominent and thus protective lip. In violent contrac- 

 tion, however, these counteracting points may be overcome. 



The condyles and tuberosities. — It should be noted that on the inner side 

 the ])rominence of the internal condyle is well marked, and that of the tiltial tuber- 

 osity is less so, while on the outer side this condition is reversed. Descending to 

 the outer tuberosity, the ilio-tibial band of the fascia lata can be traced. The more 

 distinct outer tuberosity is a good landmark for opening the joint in amputation 

 and excision. It also indicates the lower level of the synovial membrane of the 

 knee-joint. Farther back is the biceps and long external lateral ligament. The 



fio. 750.— Horizontal Section of the Knee-joint. (One-half.) 



PATELLA 

 Synovial membrane 



Capsule - 



FEMUh- 



Crueial ligaments 



Biceps 



Outer head of gastrocnemius 



Po/i/'/i'al iirlery 



EXTERXAL POPLITEAL NERVE 



I'lipliteal vein 



INTERNA L I'OPLITEAL NERVE 



External sa/Jitna rein 



.jy — Inner head of gastrocnemius 



^^ Sartnriiis 



Sartorius 

 ' Gracilis 



Semi-membranosus 

 Semi-tendinosus 



gap on the inner side between condyle and tuberosity is the place for feeling for 

 a displaced internal fibro-cartilage in ' internal derangement ' of the knee. On 

 each condyle, posteriorly, in a thin subject can be felt its tubercle, which gives 

 attachment to the lateral ligament. . Owing to their being placed behind the centre 

 of the bone these ligaments become tight in extension. On the upper part of the 

 internal condyle the adductor tubercle and the vertical tendon of the adductor 

 magnus can be felt during flexion. This bony point is a guide to the lower epi])h- 

 ysis of the femur, one of the latest to join, uniting Avith the shaft about the 

 twenty-first year. Here the exostoses in adolescents arise. The inner aspect of 

 this condyle faces ])ractically in the same direction as the head of the femur. 



Ligamentum patellae and tubercle of tibia. — These, in a well-formed leg, 

 should, with the centre of the ankle-joint, lie all in the same straight line, a useful 

 point in the adjustment of fractures (Holden). Behind the upper half of the 

 ligament is the synovial membrane of the knee-joint; below, the lower is separated 

 from the tibia by a deep bursa. In connection with all the posterior surface is fat, 

 which serves as a useful packing in the different movements of flexion and ex- 

 tension. The tubercle of the tibia is on a level with the head of the fibula. 



Prepatellar bursa. — This usually protects the patella and u})per j)art of the 

 ligamentum jiatella). It is liable to be enlarged in those who ha1)itually kneel 

 much. Its close connection with the patella and, at the sides, with the joint itself 

 is to be remembered in inflaimnations of the bursa. Usually, two processes of 



