.or, 



PATELLA. TIBIA. 



PATELLA. The patella is a sesamoid bone, developed in the ten- 

 don of the quadriceps extensor muscle, and usually described as a bone 

 of the lower extremity. It is heart-shaped in figure, the broad side 

 being directed upwards and the apex downwards, the external surface 

 convex, and the internal divided by a ridge 

 Fig. 43*. i nto two smooth surfaces, to articulate with 



condyles of the femur. The external ar- 

 ticular surface corresponding with the ex- 

 ternal condyle is the larger of the two, and 

 serves to indicate the leg to which the bone 

 belongs. 



Development. By a single centre, at 

 about the middle of the third year. 



Articulations. With the two condyles 

 of the femur. 



Attachment of Muscles. To four; the 

 rectus, cruraeus, vastus internus and vastus 

 externus, and to the ligamentum patellae. 



TIBIA. The tibia is the inner and 

 larger bone of the leg ; it is prismoid in 

 form, and divisible into a shaft, an upper 

 and lower extremity. 



The upper extremity, or head, is large, 

 and expanded on each side into two tube- 

 rosities. Upon their upper surface the tu- 

 berosities are smooth, to articulate with the 

 condyles of the femur ; the internal arti- 

 cular surface being oval and oblong, to cor- 

 respond Avith the internal condyle ; and 

 the external broad and nearly circular. Be- 

 tween the two articular surfaces is a spinous 

 process ; and in front and behind the spi- 

 nous process a rough depression, giving at- 

 tachment to the anterior and posterior 

 crucial ligaments. Between the two tube- 

 rosities on the front aspect of the bone is a 

 prominent elevation, the tultercle, for the 



insertion of the ligamentum patellae, and immediately above the 

 tubercle a smooth facet, corresponding with a bursa. Upon the 

 outer side of the external tuberosity is an articular surface, for the 



. 



* The tibia and fibula of the right leg, articulated and seen from the front. 

 1. The shaft of the tibia. 2. The inner tuberosity. 3. The outer tuberosity. 

 4. The spinous process. 5. The tubercle. 6. The internal or subcutaneous 

 surface of the shaft. 7. The lower extremity of the tibia. 8. The internal 

 malleolus. Q. The shaft of the fibula. 10. Its upper extremity. 11. Its 

 lower extremity, the external malleolus. The sharp border between 1 and 6 is 

 the crest of the tibia. 



