While working with the ca. 5,000 year old Copper Age human remains that I’m studying as part of my dissertation research, I’ve noticed that the patella tends to preserve fairly well. The patella is up there on my list of favored bones (still losing out to some of the tarsals and carpals), because it’s so easily recognizable and easy to side. It is also the largest sesamoid bone in your body, so unlike some of the other sesamoid bones, could never be confused with a subadult lunate. Bonus points to the patella!
A few quick tips: The patella is rougher anteriorly (frankly, I find the vertical striations so characteristic of the front of the patella to be one of the most distinguishing characteristics of the bone) and smooth posteriorly, where it articulates with the medial and lateral condyles of the distal femur. Superiorly it presents a relatively horizontal edge with rounded corners, while the apex, or inferior portion of the bone is noticeably pointed, leading to the bone’s distinctive triangular shape. On its posterior aspect, the lateral articular facet is larger than the medial articular facet.
The trick: If you have a relatively complete patella, orient it on a table in front of you so that the posterior surface is flat on the table and the anterior surface is facing up. Then, rotate it so that the superior-most portion is closest to you and the apex is pointing away from you. You could also think about it this way: if you propped your leg up on the table in front of you, and plucked your own patella from your leg, setting it immediately down on the table, it would be in this position. When thus oriented the patella will fall to the side that the bone is from.
I realized, long after I learned this trick (I am, quite clearly, not one of the brighter graduate students in our department), that the reason the bone falls to the side it’s from is because the lateral articular facet is larger than the medial articular facet; you could really just examine these in order to side the bone. Importantly, however, this method is a lot more fun because it’s hands-on AND you can impress unwitting by-standers with the equivalent of an osteo magic trick.
* Some day, if you really want to impress your friends at parties, I’ll give you the rundown on how to open a bottle of beer using a trowel (as taught to me by this illustrious individual). This invaluable skill has come in handy more than once over the course of my participation on various and sundry field projects.
Original Gray’s image found here.