M Articularis Genus

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Hi all

I've had a new patient, male 42yrs with an anterior superior medial knee pain and and a patella that clicks or snaps in to position during the last 1/3rd of knee extension - a bit like a trigger thumb or hallux where there's a cyst on the tendon and the interdigital joint clicks back into place on extension. However this causes no pain in the knee (and is definitely not a meniscus tear (negative Mc Murray test) before you ask)

So i'm suspecting a swelling or perturbation in the Patella cartilage that is flicking over the lateral femoral condyle edge as it drops into the patella groove (intercondylar fossa) after deviated tracking from the flexed knee position. There is no crunchiness under the knee cap normally associated with chondromalacia patella tho?

So I Dx this is a patello femoral syndrome aetiological of poor knee tracking. This was also the opinion of two physiotherpists he had seen previoulsy, however the patient's biomechanical evaluation shows no significant variations, more specifically he does not pronate very much or have any significant internal tibial rotation thru stance phase, except for two things - hallux limitus both feet at about 20dgs d/flexion [NB I mobilised his 1st MPJ to get 70dgs hallux dorsiflexion both feet] and, during walking only, the right knee tends to go into full extension quite quickly at heel strike - early stance phase and stay extended for slightly too long almost becoming hyperextended at propulsive phase, this does not happen when running tho, which tends to be when he gets the mild knee pain.

So to help me decide what to do in this case I reviewed knee anatomy and mechanics and dicovered a set of 3 small muscles I had never come across before called Articularis Genus. As I concluded I was probably not the only one I thought I would put a little study here that may be useful for those who had not.



Articular muscle of the knee--articularis genus. Ahmad I.
Abstract
Articularis genus has been considered by many as a part of the quadriceps muscle. Our observations have confirmed our opinion that this is a separate and distinct muscle. It is always present and has a discrete origin and insertion. This muscle has a very important function to perform. It elevates the capsule and the synovial membrane of the knee joint and prevents them from being pinched during extension of the leg. Thus it plays a very important role in the erect posture of humans.



"If you don't know it exists how can you treat it?" - Dr. Guy Voyer, September 2013.

The Articularis Genu is just one of the muscles that you (and a good number of therapists and trainers) can be excused for not knowing of. Not once in the 10 years I've been in the health and fitness field have I heard about it. Not once, and I've done a lot of corrective exercise and rehab' courses and qualifications! So what is it and why should you care?
The Articularis Genu is (as you can see in the picture above) a short, flat muscle located deep beneath the bulk of the Vastus Intermedius that originates from the distal third of the thigh bone and attaches to the upper border of the Patellar. It's action is to lift the Patellar upward between the Femoral Condyles (round bobbles at the bottom of the Femur) when the knee joint is extended (leg straightens - knee cap moves up). Therefore when the knee joint flexes adequate flexibility is required from the Articularis Genus to allow the Patellar to move downward in the joint space. If this flexibility is lacking the Patellar is prevented from sliding down and instead flexion forces the Patellar to compress the joint space. Repeated
compression of the joint space can and does inflame the bursae (Bursitis) which is painful, causes swelling of the knee and is generally unpleasant.


So I'm thinking if this muscle set is short/tight then it may be contributing to knee extension in walking and when running it may remain stretched, because I don't see full knee extension when running - as is usual, and so the muscle AG experiences extended internal strain causing minor pathology and painful symptoms after running.

I found an 'isolating' stretch for AG which I will try out



In the above image you can see the method of stretching the Articularis Genu that we (after much head scratching) came up with at a recent seminar with Dr. Voyer. Key to isolating the Articularis is the elevated foot which allows for the pinning of the Patellar by it's superior border, preventing it from shortening as the stretch is applied. Genius!
"When you know what it is, where it is and what it does you can treat it."

Regards dave Smith

 

Dave:

Try the diagnosis of plica syndrome. A inflamed knee plica will cause the same "popping" of the knee going into full extension. This diagnosis is quite common.

 

Very good Kevin
I was familiar with plica syndrome but thought it only caused pain in the anterior inferior medial quadrant and didn't know it caused knee popping on extension. I've spent some time following up on your lead and found out some interesting info about plica medial, lateral, supra and infra aspects. Interestingly the medial plica has it's origin at the base of the articularis genus. Just thinking out loud but it maybe that if the AG were tight it may also tighten the plica across the medial femoral condyle and cause the clicking / popping symptom without any inflammation of the plica itself and so no pathology would be noted by MRI scan as is the case with my patient.

This site also is a good read http://fixmyknee.weebly.com/medial-synovial-plica-irritation1.html
And here's a good illustration


Kevin, what's your usual treatment plan for this problem?

Great stuff - you can't buy gems like this ( well you probably could but it would cost a fortune) Cheers Dave

 

Dave:

I don't treat plica syndrome but instead refer them to my friendly orthopedic surgeon colleagues who generally will try a cortisone injection to try and calm down the inflamed plica. I have had plica syndrome before and the cortisone injection worked well for me.

Here is a good article on plica syndrome.:drinks

Medial plica irritation: diagnosis and treatment

 

Hi Dave,

I'm unable to see the image for the 'isolating' Articularis Genus stretch you and Dr. Voyer came up with, so I'm having a hard time understanding how to perform the stretch. You wrote: "Key to isolating the Articularis is the elevated foot which allows for the pinning of the Patellar by its superior border, preventing it from shortening as the stretch is applied." Would you please explain in more detail how to perform the stretch?

Thank you!

Tori

 

Here a photo Tori - its like a ilio-psoas and rectus femoris stretch but you keep the patella fixed on the ground so it cannot move proximally on the femoral condyles

 

Thanks, Dave! Have you found benefit to stretching the articularis genus for medial plica syndrome? Since the medial plica has its origin at the base of the articularis genus, this would seem like a promising treatment (where there are few).