HomeArticlesA newly discovered structure on the rectus femoris
August 25, 2022

A newly discovered structure on the rectus femoris


Researchers from University of Barcelona, Spain recently announced a newly discovered membrane at the origin of the proximal tendinous complex of the rectus femoris in the Surgical and Radiologic Anatomy journal.

The rectus femoris is the most anterior layer of the quadriceps muscle group. It is the only one of the four muscles of the quadriceps complex that crosses two joints. Besides being part of the group of flexor muscles of the hip, it also extends the knee joint, and stabilizes the pelvis in the standing position.

Rectus femoris has a proximal tendinous complex  which is constituted by a direct tendon, an indirect tendon, and a variable third head. Direct and indirect tendons finally converge into a common tendon. All the proximal tendinous comples shows a medially sloping in its proximal insertion.

Researchers from University of Barcelona, noticed a membrane connecting the common tendon with the anterior superior iliac spine. Such membrane constitutes a new origin of the proximal tendon complex. However the membrane could be just an anatomical variation.

Thus to confirm its existance, the researchers conducted a study by dissecting 42 cadaveric lower limbs and examined the architecture of the proximal tendon complex.

The researchers showed that the membrane is a constant component of the proximal tendon comples. It has a lateral to medial trajectory and is in relation to the common tendon, the direct, and indirect tendons, which present a medial slope.

This suggests that the membrane has a role as stabilizer role for the proximal tendon complex, acting as a corrector of the inclined vector of the complex.

The authors concluded that as rectus femoris injuries are frequent in football, the newly discovered membrane is a constant component of the proximal tendon complex and its integrity should be included in the algorithm to diagnose injuries.

Author and instructor Dr. Joe Muscolino said
“When I first hear about “exciting new” anatomic discoveries, I tend to be skeptical. Anyone spending much time in the cadaver lab sees that muscles throw their fibrous attachments pretty much everywhere around their stated bony attachments, so variations are very common. But to hear that a new variation is less a variation than a constant anatomic feature is exciting!”
Great and fun geeky news that will likely have ramifications for most all our clients! 
New Structure on Rectus Femoris, A comment by Robert Schleip

For people with experience in dissection, this paper is anything but a complete surprise. Whoever has tried to ‚dissect‘ ligamentous or tendinous structures, as shown in standard anatomy books, knows that these are artificial abstractions, which the human investigator carefully separates more or less arbitrarily from a much more complex surrounding fascial network. For example, the answer to the question where the most distal tendinous attachment of the tensor fasciae latae occurs – at the fibular head, the proximal tibial tuberosity, or much further down? – has less to do with the given individual anatomy than with the dissection focus and skill of the investigator.
 
Nevertheless, many manual practitioners, as well as movement educators, are proud of their detailed knowledge – often much more specific than other health professions – about the major attachments of most of the major muscles in the human body. Concerning the hip joint, they would not hesitate too long to list those inferior muscles that clearly attach to the Anterior Superior Iliac Spine (ASIS) of the pelvic crest, in contrast to those hip-crossing muscles for which this is not the case. They would probably agree, that when it comes to that question, then the Sartorius muscle, tensor fasciae latae and gluteus medius do regularly express such an attachment; but not so – or to a much lesser degree – the adductor muscles, the quadriceps femoris, or hamstring muscles. This has been the case 50 years ago, also 100 years ago, and also most recently.
 
This nicely done anatomical study now suggests that the rectus femoris muscle (as part of the quadriceps compartment) should be clearly included among those hip-crossing muscles that attach to the ASIS. Yes, some great pioneers had predicted and clearly described this additional attachment as a frequent “variation”. Such descriptions (of frequent variations) typically have less chances of altering the teaching in conventional school medicine, or in standard anatomy books. For example, Thomas Myers wrote about the rectus femoris in the most recent edition of his best-selling book ‘Anatomy Trains – Myofascial Meridians for Manual Therapists & Movement Professionals’
 
„Palpation and dissection reveals that in some undetermined percentage of the population there is an additional significant fascial attachment of this muscle into the ASIS“ (page 58).
 
This new anatomical paper now specifies the “undetermined percentage of the population” to something close to 100%! When examining 42 half-pelvises in their thorough investigation, the authors found this additional proximal attachment of the rectus femoris to the ASS in all of them. In addition, the anatomical photography and measurements which the authors provided, demonstrate that this tendinous attachment is not a flimsy one – i.e. that the investigator needs to carefully dissect in a “fibre by fibre” approach – but constitutes in the majority of cases a fairly large and substantial structure, comparable to the magnitude of the other two standard proximal attachments of this muscle.
 
We could now conduct a nice betting competition with each other, how many years it will take until this proximal connection of the rectus femoris will be re-drawn in standard anatomy books. Maybe 3 years, 5 years, 10 years, or never? I would lean on the side towards 5 years, for books like the leading Gray’s Anatomy atlas (British edition), and probably longer for some of the others.
 
Whoever followed the constructive scientific debates around the question which of the myofascial force transmission lines suggested by Tom Myers are more or less wishful-thinking based projections and which ones are impressively congruent with current anatomical evidence1), is probably aware that the pelvis-crossing connection of the Superficial Front Line has been critiqued as expressing much less anatomical evidence (of a direct myofascial fibre continuity in the same direction) than is the case for its counterpart, the Superficial Back Line. This new article now suggests that this critique may have to re-visit this important connection with this novel anatomical information.
 
It will also be interesting to watch if the official description of these “myofascial meridians” by Tom Myers and his peers may possibly extend the standard description and illustration of this line in future years to include not only the myofascial tissues of the rectus abdominis as next superior step above the pelvis but may now also include more lateral inferior portions of the anterior rectus sheet with its continuation into the aponeurosis of the external oblique muscle. This dense fascial sheet attaches to the ASIS and therefore constitutes an appealing direct myofascial fibre continuity (and potential force transmission?) from the rectus femoris towards the middle upper abdomen. In addition, the exceptional recent work of Jan-Paul van Wingerden showed that this anterior rectus sheet expresses a very different morphology (as well as force transmission function, plus also different adherence with the rectus muscle) than does the inferior rectus sheet2). Let me, therefore, suggest that these novel anatomical insights, which were not available ten years ago, indicate that a possible inclusion of the anterior rectus sheet into the Superficial Front Line might be worth a renewed reconsideration.
 
Interestingly, this new scientific article discusses the implications of their novel finding for the field of sports medicine. As the proximal insertion of the rectus femoris is a frequent site of muscular strain injuries in sports that require dynamic kicking and sprinting, the authors suggest future imaging investigations. Let me suggest possibly also palpatory exploration – should be included in assessing such pathologies. I would also propose that manual practitioners wanting to affect tonus regulation of the quadriceps muscle might profit from extending their manual focus to the ASIS. It can be similarly as they have learned in previously to include a direct treatment of the sacrotuberous ligament when wanting to influence tonus regulation of the hamstring muscles, based on the direct fibre-continuity of the biceps femoris with this intrapelvic ligament3). And of course, similar applications can easily be created for foam rolling, stretching or local warming temperature applications.
 

1) Wilke J et al (2016) What Is Evidence-Based About Myofascial Chains: A Systematic Review. Arch Phys Med Rehabil 97: 454-461.

2) van Wingerden JP et al. (2020) Anterior and posterior rectus abdominis sheath stiffness in relation to diastasis recti: Abdominal wall training or not? J Bodyw Mov Ther 24: 147-153.

3) Bierry G et al. (2014) Sacrotuberous ligament: relationship to normal, torn, and retracted hamstring tendons on MR images. Radiology 271: 162-171.  

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