Anatomy can, and does, change.
The image above is a comparison of a normal Left thigh (quadriceps muscle group) with the newly discovered muscle in RED, the kneecap (patella) is located at the bottom of the image. Traditionally, there are 4 muscles that compose this group: Vastus Lateralis (2-VL), Vastus Intermedius (3-VI), Rectus Femoris (5-RF) and Vastus Medialis (6-VM). Here is a link to the article by Grob et al (2016), recently submitted to the journal Clinical Anatomy. http://www.ncbi.nlm.nih.gov/pubmed/26732825
Because anatomy rarely changes, it is exciting for the scientific and medical communities when research such as this is released. As I just stated, traditionally the quadriceps consist of 4 distinct muscles on the front (anterior) portion of your thigh. These muscles act mainly as knee extensors (i.e. kicking a ball in front of you) and contribute slightly to hip flexion.
Considering I am currently teaching lower extremity anatomy in my undergrad course, I will absolutely investigate some cadavers in the upcoming week. Let's see what I can find...
What's the big deal?
The finding of this muscle, which was identified on 26/26 cadavers in this study, implies that the Vastus Intermedius (3-VI) is impacted by a separate and independent structure. This structure was given the name "tensor of vastus intermedius", as it's contractile fibers apparently pull/tense the larger vastus intermedius muscle. This study also indicates this new structure is supplied by distinct blood vessels and nerves, further contributing to the notion that this is an true muscle. The ramifications of this research would likely impact imaging procedures like MRIs, physical therapy/corrective exercises, massage techniques and certain surgical procedures.
Although our understanding of the human body is quite extensive...nothing is 100% accurate. MEDICINE IS STILL AN IMPERFECT SCIENCE, EVEN WITH QUANTIFIABLE TRUTHS. We as humans are fallible creatures and therefore anything we participate in has fallibility, including the assessment of anatomy.
To illustrate this point again, look at the image of a Right knee below.
The researchers hypothesize that this ligament is responsible for limiting certain rotation forces in the knee joint. Additionally, this ligament may actually be the structure damaged when ACL injuries are thought to occur. This notion may support the relatively high number of unsuccessful ACL repairs.
I hope you share in my excitement as we introduce the world to the tensor of vastus intermedius. Ok, maybe not the whole world, but rather the finite group of anatomy dorks like myself. As always, I value feedback and look forward to hearing from you.