[First Figure of Chapter 32]

First figure of the thirty-second chapter, showing the anterior face of the patella.

[Second Figure of Chapter 32]

Second figure, setting forth the posterior surface of the patella.

Index of characters in the second figure

The situation and form of the patella
A certain round bone [patella] (all of figs. 1, 2 and C on the skeletons) is situated in front of the anterior surface of the knee joint, not unlike a small shield. ⁵ On its posterior surface [facies articularis] where it faces the femur, it is seen for the most part covered with smooth, slippery cartilage [cartilago articularis], its swelling and depressions elegantly matching the anterior surface [facies patellaris] (H in fig. 2, ch. 30) of the lower heads [condylus medialis, condylus lateralis] of the femur. Along its longitude, it projects with a wide and moderately protruding eminence [eminentia recta] (A, B in fig. 2) which enters the wide depression [facies patellaris] carved in the anterior of the femoral heads. On each side (C, D in fig. 2) of this eminence there is a depression [facet] that receives the projecting surfaces of the femoral heads, which are coated with cartilage [c. articularis]. But as the outer head [condylus lateralis] of the femur extends forward more than the inner [condylus medialis], and is covered with smooth cartilage over a larger area, so too the outer depression of the patella, situated at the outer side of its eminence, is much larger and wider than the inner. Therefore in that part where it makes contact with the femur the patella is smooth and slippery, like the femur. ⁶ On its anterior surface [facies anterior] (all of fig. 1) and on its sides it appears rough and covered with certain small, blind foramina; ⁷ similarly in its posterior surface, where in its lowest part [apex patellae] (E in fig. 2) it is brought downward as if in a sharp process and faces the upper end of the tibia, it is rough and equipped with those small foramina so as to attach better and more strongly to the tendons ⁸ that extend the tibia.

How the patella is connected to the femur
The whole patella (k in the 8th table of muscles), over the entire breadth and surface that is not covered with slippery cartilage, is attached to those tendons and is not connected to femur or tibia

The substance of the patella
The substance of the patella in older persons is quite hard and solid, notwithstanding Galen’s assertion that it is cartilaginous on the outside; ¹¹ Marinus likewise, among other prominent anatomists, independently called it a cartilaginous bone and devoted a chapter to it in a book which he wrote, On Cartilaginous Bones. ¹² These authors were perhaps thinking of the material of the tendons to which the patella is attached, which when boiled resembles soft cartilage, like the parts from which the sinewy heads of the muscles or the ligaments take their origin or into which they are inserted. But when the patella is properly cleaned of tendons ¹³ it is seen to be in no way cartilaginous, but quite solid and strong not only in humans but also in cattle, sheep, and other quadrupeds. Before their knee joint, as well, the Maker of things placed a patella, much longer and narrower than in humans, as in most birds it is wider and shorter. ¹⁴

The use of the patella ¹⁵
The patella is given to humans and the animals I have just mentioned so the knee joint may be more dependably extended forward into an angle and straightened only into a straight line from an angular flexion. The patella is also particularly responsible for preventing the femur from dislocating forward out of the depressions of the tibia in flexion of the lower leg. Those whose patella has been removed from its place, or has been accidentally broken into two parts and ascends much higher than the lower heads of the femur [condylus medialis, condylus lateralis] (E, F in fig. 2, ch. 30), particularly teach us this use. ¹⁶ For they flex the tibia very weakly and go down steep places and steps with the greatest peril because the femur is always slipping forward when there is no strength in the knee. ¹⁷