256 





which is derived from the Rectus femoris and Vastus intermedius. The medial and 

 lateral borders are thinner and converge below: they give attachment to those 

 portions of the Quadriceps femoris which are derived from the Vasti lateralis and 

 medialis. 



Apex. The apex is pointed, and gives attachment to the ligamentum patellae. 



Structure. The patella consists of a nearly uniform dense cancellous tissue, covered by a 

 thin compact lamina. The cancelli immediately beneath the anterior surface are arranged 

 parallel with it. In the rest of the bone they radiate from the articular surface toward the other 

 parts of the bone. 



Ossification. The patella is ossified from a single center, which usually makes its appearance 

 in the second or third year, but may be delayed until the sixth year. More rarely, the bone is 

 developed by two centers, placed side by side. Ossification is completed about the age of puberty. 



Articulation. The patella articulates with the femur. 



Tuberosity 





Intercondyloid, eminence 



FIG. 257. Upper surface of right tibia. 



The Tibia (Shin Bone). 



The tibia (Figs. 258, 259) is situated at the medial side of the leg, and, 

 excepting the femur, is the longest bone of the skeleton. It is prismoid in form, 



expanded above, where it enters into the 

 knee-joint, contracted in the lower third, 

 and again enlarged but to a lesser extent 

 below. In the male, its direction is vertical, 

 and parallel with the bone of the opposite 

 side; but in the female it has a slightly 

 oblique direction downward and lateralward, 

 to compensate for the greater obliquity of 

 the femur. It has a body and two extremities. 

 The Upper Extremity (proximal extremity). 

 The upper extremity is large, and expanded 

 into tw r o eminences, the medial and lateral 

 condyles. The superior articular surface pre- 

 sents two smooth articular facets (Fig. 257). 

 The medial facet, oval in shape, is slightly 

 concave from side to side, and from before 

 backward. The lateral, nearly circular, is 



concave from side to side, but slightly convex from before backward, especially 

 at its posterior part, where it is prolonged on to the posterior surface for a 

 short distance. The central portions of these facets articulate with the con- 

 dyles of the femur, while their peripheral portions support the menisci of the 

 knee-joint, w r hich here intervene between the two bones. Between the artic- 

 ular facets, but nearer the posterior .than the anterior aspect of the bone, is the 

 intercondyloid eminence (spine of tibia), surmounted on either side by a prominent 

 tubercle, on to the sides of which the articular facets are prolonged; in front of 

 and behind the intercondyloid eminence are rough depressions for the attachment 

 of the anterior and posterior cruciate ligaments and the menisci. The anterior 

 surfaces of the condyles are continuous with one another, forming a large somewhat 

 flattened area ; this area is triangular, broad above, and perforated by large vascular 

 foramina; narrow below where it ends in a large oblong elevation, the tuberosity of 

 the tibia, which gives attachment to the ligamentum patellse; a bursa intervenes 

 bet\veen the deep surface of the ligament and the part of the bone immediately 

 above the tuberosity. Posteriorly, the condyles are separated from each other by 

 a shallow depression, the posterior intercondyloid fossa, which gives attachment to 

 part of the posterior cruciate ligament of the knee-joint. The medial condyle 

 presents posteriorly a deep transverse groove, for the insertion of the tendon of 



