Joined: February 27, 2005
VMO inhibition occurrs for two reasons, firstly , the L3 nerve root is irritated by a temporary inflammatory event at the L3/4 facet joint, brought about by hypomobility at that joint as a response to protective tonic changes around it . This leads to a loss of normal recruitment patterns at VMO, along with the prospect of medial leg/knee referred pain. ( sometimes confused with medial ligament /meniscal damage ). Secondary inhibition may occurr around the knee , including VMO once the patella has left it's normal track over time ( as permitted by VMO dysfunction ) , giving rise to swelling , inflammatory change local to the retro patella bursa etc , and pain . The cart, is the L3 irritation , the horse, is VMO inhibition , the rider, knee pain and further local changes . To restore normal VMO recruitment and make the whole schemozzle go away, CM to L3 , about ten minutes usually enough to restore normal VMO recruitment , further attention to adjacent joints and a biomechanical workup to establish cause of the protective event to provide cure. Should take no more than three treatments for a good pair of hands.
Joined: April 13, 2006
Real time MRI shows that it's the femur rotating under the patella (which remains virtually immobile in a med-lat plane) and not the patella "riding" laterally as previously assumed. Throw on top of that that it's not so much a weak VMO but a VMO not firing at the correct time (if one still follows the belief that it's a patellar tracking problem) and the difference is in MILLISECONDS.
Transverse plane control (ie LE pronation control) seems to be your best bet with the current evidence. And, what the heck, press on the L3/4 facet on that side for a while. Won't hurt the pt.
Joined: December 11, 2004
From: Middletown, PA
I disagree with the VMO being a cause of PF problems. I believe it to be more in the hip or in the gait. In a functional evaluation you may find things in the hip that need to be addressed. I strengthen the hip and the quad, and use manual stretching techniques (not specific to any portion) in treating most PF problems. Doctors, and therapists, will often want the VMO to be addressed. What happened to the VMO in a long distance marathon runner that he is now having this pain? The quads are strong. I like how one researcher put it. "The patellafemoral complex is like a train on tracks and the tracks are running out from under the train." The train is riding properly most of the time. The quads which are really of no direct consequence here in the end (I could not treat the quad at all and get some of these cases better). How do we affect the femor though? Through addressing the hip and sometimes the feet. I would challenge you to not tape and not do ANY OKC exercises and treat the hip.
STUDY DESIGN: Single-group, repeated-measures design. OBJECTIVE: To compare patellofemoral joint kinematics during weight-bearing and non-weight-bearing knee extension in persons with lateral subluxation of the patella. BACKGROUND: The only previous study to quantify differences in patellofemoral joint kinematics during weight-bearing and non-weight-bearing tasks was limited in that static loading conditions were utilized. Differences in patellofemoral joint kinematics between weight-bearing and non-weight-bearing conditions have not been quantified during dynamic movement. METHODS AND MEASURES: Six females with a diagnosis of patellofemoral pain and lateral subluxation of the patella participated. Using kinematic magnetic resonance imaging, axial images of the patellofemoral joint were obtained as subjects extended their knee from 45 degrees to 0 degrees during non-weight-bearing (5% body weight resistance) and weight-bearing (unilateral squat) conditions. Measurements of patellofemoral joint relationships (medial/lateral patellar displacement and patellar tilt), as well as femur and patella rotations relative to an external reference system (ie, the image field of view), were obtained at 3 degrees increments during knee extension. RESULTS: During non-weight-bearing knee extension, lateral patellar displacement was more pronounced than during the weight-bearing condition between 30 degrees and 12 degrees of knee extension, with statistical significance being reached at 27 degrees, 24 degrees, and 21 degrees. No differences in lateral patellar tilt were observed between conditions (P = .065). During the weight-bearing condition, internal femoral rotation was significantly greater than during the non-weight-bearing condition as the knee extended from 18 degrees to 0 degrees. During the non-weight-bearing condition, the amount of lateral patellar rotation was significantly greater than during the weight-bearing condition throughout the range of motion tested. CONCLUSIONS:The results of this study demonstrated that lateral patellar displacement was more pronounced during non-weight-bearing knee extension compared to weight-bearing knee extension in persons with lateral patellar subluxation. In addition, the results of this investigation suggest that the patellofemoral joint kinematics during non-weight-bearing could be characterized as the patella rotating on the femur, while the patellofemoral joint kinematics during the weight-bearing condition could be characterized as the femur rotating underneath the patella.
PMID: 14669963 [PubMed - indexed for MEDLINE]
I agree with Rwantz and treat hip focusing on pronation control and LE flexibility as appropriate. Generally have excellent outcomes. But, truthfully, don't have any data using OKC and patellar taping to compare against from my practice.
< Message edited by jlharris -- August 15, 2007 3:35:02 AM >
Joined: December 22, 2006
Hi - what is LE??
My brother and i are physical therapists - he is a VMO timing retraining boy and he gets great results. I don;t do it and still get good results.
In general, i believe changing the femur's control via the lumbopelvic-hip and feet wil be so much more useful than VMO exercises...and i am from Australia (land of Jenny McConnell's taping and exercises!!)
Joined: April 26, 2002
First, describing the kinematics as the patella rotating under the femur or the femur moving from under the patella is simplified biomechanics and not technically correct. The patella doesn't move on its own during gait. It moves because of the forces acting on it which in the case of the patella would be the quads, the femoral groove, the capsule, the patellar ligament and gravity.
It makes intuitive sense that an imbalance in force production between the quads could cause a shift in patellar position with respect to the femur. Most people assume that the muscle acts along the direction of its fibers. This is actually an incorrect assumption. The force a muscle generates is more generated in the direction of its aponeuroses than along its fiber direction. In an experiment that will be presented at the American Society for Biomechanics meeting later this week, we transected vastus medialis (I'll let your imagination figure out how) and looked at patellar joint pressures. We found no change in peak pressure, no change in patellar position and only a minor decrease in medial facet pressure with no increase in lateral joint pressure.
How would hip position change patellar tracking? Possibly by changing line of muscle pull but this is unlikely. Change in patellar tendon angle is more likely. internal rotation of the femur will lead to external rotation of the tibia. this will lead to a lateral force on the patella. I have first hand experience with this. My patella has a habit of dislocating. Most of the time this occurs with little muscular contraction when my foot slips out from under me and my tibia laterally rotates.
This does not mean that quads training or patella taping can not be effective. In fact I believe that quads strengthening is still has fairly strong evidence behind it. That doesn't mean that it works by changing tracking. Taping is effective as well. It is quite unlikely that it has much of a mechanical effect.
I think we are doing our profession a disservice by using simplified biomechanics such as the femur rotating under the patella, or open/closed chain exercises, or muscles working reverse origin/insertion.
The idea of isolating the VMO comes from the innervation shared with the adductors (mostly embryonic studies) versus the other muscle of the quad group. There is research that demonstrates higher muscle recruitment with isometric adduction strength during quad strength, but this doesn't imply "muscle isolation". There is some information out there about selective inhibition too, but this has been deemed inaccurate with further study. While it is certainly a possibility, I would think that L3 is not a very common cause of PF dysfunction (that is just my opinion). I tend to lean toward rotation forces that lead to lateral force on the knee during gait. The feet> hips tend to be where I start to looks. Just the same, I usually include SLR with hip ER and SAQ's with isometric hip adduction as part of my plan. And I guess I'll give the back a second look now!
Joined: April 13, 2006
Since Adam resurrected this post, I'll jump back in. To BournePhysio, how is poor neurmuscular control at the hip leading to IR/Pornation of the femur, and subsequantly (as the authors of the study describe it) "the femur rotating underneath the patella", as you say, "doing our profession a disservice"? I guess I am unsure of the point you are making in your post regarding the "cause" of petellofemoral pain. Please ellaborate. It seems you are are agreeing with the authors of the study I posted but arguing against it at the same time
Joined: April 26, 2002
Thanks Sebastian, You nailed the most important factors.
Thanks jlharris, you very nicely illustrated why this is doing our profession a disservice. In your explanation you completely left out the role of the tibia and patellar tendon. I would suggest that this is by far the most important factor. Try this; stand on one leg and internally rotate the other leg at the hip. Do you think that the femur rotated under the patella? No. They both rotated together. Wait a second that?s ?open chain?. Let?s try that ?closed chain?. Internally rotate the femur that you are standing on. Do you think that the femur rotated under the patella? No. But that?s ?reverse origin/insertion? Do the same thing but standing on a wobble board and hold something so that your leg internally rotates under your body. How about now? No. Now maybe you don?t have subluxing patellae but I can almost guarantee that it wouldn?t matter. The muscles at the hip just don?t have the mechanical advantage to do much to the patella with these movements. The patellar tendon does. If in the above study they externally rotated the hips such that subjects thighs stayed in the sagittal plane but the same ER of the tibias was maintained, I suspect that you would see the same relative movement of the patella with respect to the femur (or the femur with respect to the patella).
This leads me to my next point. Terminology. It is perfectly valid to describe the movement of one bone with respect to the other by using either bone as the reference. It is standard in biomechanics to describe movement of the distal bone with respect to the proximal bone. In this instance the patella with respect to the femur. So while it is perfectly valid to describe motion this way it goes against convention and thus can be confusing to readers. So a medial translation of the patella with respect to the femur is the same thing as a lateral translation of the femur with respect to the patella (assuming aligned coordinate systems). So with these definitions in mind, it is absurd to say that it is not the patella rotating on the femur but it is actually the femur rotating on the patella. Powers, instead of using the patella or the femur as a reference frame, used a global reference frame. I?m sure most physios don?t understand what that means. He is basically arguing that because the femoral groove is moving more medial in the global coordinate system that you can say that the femur is rotating under the patella. This is a very weak argument as the medial movement could be completely incidental and have nothing to do with the relative movement between the patella and femur. I highly doubt that this would have been accepted in a biomechanics journal as written and I am surprised that this came out of Powers lab let alone with Powers as first author.
On a completely different note. Why did ginger revive a seven year old thread?
Joined: April 13, 2006
...internally rotate the femur that you are standing on. Do you think that the femur rotated under the patella? No.
Powers study concludes it does. That is what I have to go on for now. Do you have a paper (or papers) that would demonstrate otherwise?
The muscles at the hip just don?t have the mechanical advantage to do much to the patella with these movements.
I don't imply they do. But they do have a direct effect on femoral positioning in weight bearing in the frontal, sagittal and transverse planes. Because of this, there is a 2° effect on petellofemoral and tibiofemoral positioning with dynamic activity. This can very likely effect the patella tendon itself.
On a side note, I read a paper by two orthopaedic surgeons that looked at what structures in the knee where the most sensitive. The one operated on the other arthroscopically w/o anesthia. The first "poked" on the different structures (patella, femoral condyles, patella tendon, patellar fat pad, etc) and the other rated the pain on a 0-5 scale. Which ended up being the most painful? The underside or the patella? Nope, it was the infrapetellar fat pad. Very interesting in terms of our thought of pain coming from the patella d/t "mal-tracking". Will try to find the reference and post it.
above study they externally rotated the hips such that subjects thighs stayed in the sagittal plane but the same ER of the tibias was maintained, I suspect that you would see the same relative movement of the patella with respect to the femur (or the femur with respect to the patella).
Your suspicion would be your opinion. I do think this would be a great next step for the authors to take in their research. I'd suspect it would change, but it's only both of our opinions as the research (as far as I know) has not been done to show which or us is more correct.
This is a very weak argument as the medial movement could be completely incidental and have nothing to do with the relative movement between the patella and femur. I highly doubt that this would have been accepted in a biomechanics journal as written and I am surprised that this came out of Powers lab let alone with Powers as first author.
As you have so bluntly pointed out I am not a biomachanist (?sp), although I'm not completely ignorant either. With that said, I'm still unsure of what your opinion is that is occuring as the most frequent/main/primary culprit leading to petellofemoral pain?
Joined: April 13, 2006
Thanks jlharris, you very nicely illustrated why this is doing our profession a disservice. ... ...Terminology. It is perfectly valid to describe the movement of one bone with respect to the other by using either bone as the reference. It is standard in biomechanics to describe movement of the distal bone with respect to the proximal bone. ... So while it is perfectly valid to describe motion this way it goes against convention and thus can be confusing to readers... ...Powers, instead of using the patella or the femur as a reference frame, used a global reference frame. I?m sure most physios don?t understand what that means....
PT's don't understand biomechanical terminology and convention; but it's a disservice to the PT profession because we describe something in a non-conventional way? I think it would do a biomechanic's profession a disservice by not sticking to common convention. But if PT's don't know any better, how can we abide by something we don't understand?
I know for sure engineer's cringe at our bastardization of the terms "Open Kinetic Chain" and "Closed Kinetic Chain". These terms are consistantly missused in terms of common convention in engineering; but are widely understood as related to PT intervention and discription.
Point is, the hypothesis of poor neuromuscular control at the hip being the 1° factor in "petellofemoral" pain may be incorrect - although not disproven yet - nitpicking "femur rotating" as a disservice to PT (again, maybe biomechanics) as a way to discredit this hypothesis in not valid.
Sincerely would like to hear your "operating" hypothesis as to the precipitating factor(s) in petellofemoral pain.
Recap of posted theories:
1. Poor VMO strength/timing/recruitment
2. L3 hypomobility and facet irratation
3. Poor neurmuscular control and or strength at the hip, particularly in the transverse plane (pronation control) causing mal-tracking of the patella in relation to the femoral groove causing irration of ??? (patellar tendon? Infrapatellar fat pad? patella itself?)