124 



THE BONES- OF THE LOWER LIMB. 



THE PATELLA. 



The patella, rotula, or knee-pan, situated at the front of the knee-joint, is a 

 sesamoid bone developed in the tendon of the quadriceps extensor cruris. It is 

 compressed from before backwards, and somewhat triangular in shape, with the 

 apex below. Its anterior surface is convex and longitudinally striated, being 

 covered by a fibrous prolongation from the extensor tendon ; it presents a few 



A.. 



Fig. 138. RIGHT PATELLA : 



A, FROM BEFORE ; B, FRO II 



BEHIND. (Drawn by T. 

 W. P. Lawrence.) g- 



In B, the articular surface 

 is seen, divided by a ridge into 

 a smaller internal and a larger 

 external part. On each of 

 these three facets may be re- 

 cognized, of which the middle 

 is the largest and the lower 

 the smallest, while along the 

 inner margin there is a narrow 

 seventh facet. 



vascular foramina, and is separated from the skin by one or more bursse. The 

 superior border is broad, and sloped from behind downwards and forwards ; it is 

 occupied, except near the posterior margin, by an impression into which the 

 common (suprapatellar) tendon of the quadriceps is inserted. The deep surface is 

 for the most part coated with cartilage for articulation with the femur, and is 

 divided by a vertical elevation into two parts, the external of which is the larger 

 and transversely concave, while the internal is convex : below the articular surface 

 is a triangular depressed and roughened area, covered in the recent state by a mass 

 of fat ; and from the lower angle and sharp margins of this part of the bone the 

 infrapatellar tendon or ligamentum patellse springs, by which the patella is 

 attached to the tibia. 



THE TIBIA. 



The tibia, or shin-bone, is, next to the femur, the longest bone in the skeleton. 

 It is the anterior and inner of. the two bones of the leg, and alone communicates 

 the weight of the trunk to the foot. It articulates with the femur, fibula, and 

 astragalus. 



The superior extremity or head is thick and expanded, broader from side to 

 side than from before back, and inclined somewhat backwards from the direction of 

 the shaft. It forms on each side a massive eminence or tuberosity, on the upper 

 aspect of which is a slightly concave articular surface for the corresponding 

 condyle of the femur. The internal tuberosity, somewhat larger than the external, 

 is rounded, and marked posteriorly by a horizontal groove for the insertion of the 

 semimembranosus muscle. The external tuberosity forms at the junction of its 

 anterior and outer surfaces a broad prominent tubercle, into which the ilio-tibial 

 band of the fascia lata is inserted ; at its posterior and under part is a small flat 

 surface for articulation with the head of the fibula. The internal condylar surface 

 is oval in shape, larger than the external, and slightly more hollowed. The external 

 condylar surface is more nearly circular, and concave from side to side, but rather 

 concavo-convex (in some cases altogether convex) from before backwards, and is 

 prolonged for a short distance on the posterior surface of the tuberosity where 

 the tendon of the popliteus glides. The peripheral part of each articular 

 surface is flattened, and separated from the condyle of the femur by a semi- 

 lunar interarticular fibro-cartilage. Between the condylar surfaces is an irregular 



