At what age does the patella form in an infant?

TThe patella, or knee cap, is a triangular bone, about 5 cm in diameter and embedded in the tendon of insertion of the quadriceps femoris muscle - one of the largest and most powerful muscles in the body that extends the leg.

At about 7.5 weeks of development the patella's primordium or anlage (German, an outline) is distinguishable in the quadriceps muscle. After the sixth month of fetal life the patella increases in size at about the same rate as the other bones of the lower limb. The patella ossifies from several centers which appear during early childhood and later fuse. 50% appear by 2.5 yrs in females and 4 yrs of age in males. Ossification is usually completed by puberty or adolescence.