Detailed guides to painful problems, treatments & more

Flabbergasted by the fabella

 •  • by Paul Ingraham

Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of PainScience.com: a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

How did I not know about this? After a good solid decade of reading regularly and widely about knee pain, I am flabbergasted that I had never heard of the fabella.

Some folks have an extra knee bone, a sort of second kneecap in back — the f-for fabella instead of the p-for-patella — embedded in the tendon of the gastrocnemius muscle.

How many people have this osseous oddity? Apparently it’s not clear. Driessen et al: “The presence of the fabella in humans varies widely and is reported in the literature to range from 20% to 87%.” That’s quite a range!

It may form for the same reason the patella is there (leverage, high stresses), and it can get to hurting just like the patella (fabella syndome).

Filed under “well I be danged”! And I’ve added it to the patellofemoral syndrome tutorial, of course — mainly for the novelty of it, since fabella syndrome isn’t likely to be confused with kneecap pain.