Effective Quadriceps Training in Patellofemoral Pain

Original Editor - Stacy Schiurring based on the course by Claire Robertson

Top Contributors - Stacy Schiurring, Jess Bell and Kim Jackson

Introduction

Research into the cause of patellofemoral pain has been ongoing for decades. Looking back into the history of rehabilitation medicine, in the 1990's-2000's it was believed that deficits of the vastus medialis oblique (VMO) of the quadriceps was the culprit behind patellofemoral pain. Early research often used fixed cadavers rather than live subjects meaning the data had limited applicability and external validity with that literature. More recently, research has utilised electromyography (EMG) of the VMO in isolation. While studying the VMO in isolation is not entirely unuseful, it limits the study's application to clinical practice.

In more recent years, research has expanded to looking up and down the kinetic chain for a more holistic cause of patellofemoral pain. While there is a large volume of research around the quadriceps, in particular the VMO, it does not link causality to the quadriceps as the most likely problem or cause of patellofemoral pain. However, this does point to a way of predicting which rehabilitation patient will have VMO related patellofemoral pain.

Patellofemoral Joint Kinematics

ADD REVIEW OF JOINT BIOMECHANICS

So, we need to think about the kinematic of the patellofemoral joint. So, the patella sitting well, relative to the trochlea, so that we get that even loading, we don't get hotspots of pressure which are undesirable. So, when do we get an alteration in kinematic? We certainly get it when we get 0% pull from the vastus medialis. Now, you might say, well, when do we ever have 0%? Well, we do. We have a couple of scenarios that, where this does actually still become relevant.

So, the first one is swelling. So, right back in 1984, Maria Stokes showed very elegantly that it takes 40 mils of fluid to inhibit the vastus lateralis and it only takes 10 to inhibit the vastus medialis. So, when is this relevant? Well, this is absolutely therefore relevant in the case of a small effusion. And we do see this in those patients that perhaps have gone for minor knee surgery, maybe an arthroscopic meniscectomy, and the meniscectomy side of things is fine and then all of a sudden, they present with patellofemoral pain. And I think often in those situations that effusion has just kicked off some real shut down in the vastus medialis that has then driven some patellofemoral pain, probably in conjunction with other risk factors that were already there.

Other scenarios that would give a similar effect would be post-dislocation, or a heavy fall onto the knee. And in fact, it's been shown that, and I'm talking about in people that don't fracture, it's been shown that about 50% of all of those patients will have pain at a year and they often have an effusion as well. A heavy fall onto the knee could be quite problematical. So, these situations where there's a very identifiable moment, whether it be surgery, dislocation, trauma has set off an effusion and effusion creates a dramatic change in their dynamic stability. So, swelling is definitely something to really take note of and absolutely if you can't work out why the effusion is there, particularly in an adolescent, that needs urgent investigation. So, is there something systemic going on driving that inflammation? Is it that there's something like osteochondritis dissecans, whatever? It is not normal to have an unexplained effusion.

Okay. Moving on from swelling, the other source of immediate change in dynamic firing of the VMO is the pain, the presence of pain. So, actually we are looking therefore at a similar group of patients, those ones that have had surgery, dislocation, fall, something where suddenly, and very identifiably they've had an onset of a lot of pain. And what we know that this does is this really disrupts the firing. And Paul Hodges, very elegantly, has shown if you inject the fat pad, which is very pain sensitive, with saline, it will immediately slow the firing of the VMO. And the more you inject, then the more profound that is. So, I think we do need to look out for this subgroup, if you like, of patellofemoral pain patients who can identify as sudden onset of pain or swelling and that's an immediate big clue that they probably are a good candidate to be doing quads work. However, don't forget of course, if you have a painful knee, for whatever reason, for long enough that in itself will drive secondary VMO sluggishness, poor performance, and over time, the atrophy will create architecture change and we'll talk about the architecture change in a minute.

Quadricep Muscle Architecture

So, believe it or not, even as recently as 2005, there was still debate going on: was the VMO even separate from the VML? So, in other words, is the VM split into two areas, the VMO and the VML? And there was a bit of debate with a couple of papers, one by Ono, one by Peeler coming out quickly disputing this. And so, I teamed up with an anatomist and we decided to try put this argument to bed by ultrasounding a large volume of knees. So, we ultrasounded 80 knees to see if we could describe the anatomy and what we found was very interesting. So, not only did we find the VMO was a separate entity, and we can say it's got a fascial plane between the VMO and the VML, it's got a different origin on the adductor muscles, different fibre orientation, different nerve distribution, so it's clearly a separate entity.

But not only did we find that, we also found that the anatomy varied a lot across the population. So, we found some people had a VMO that its fibre was around 40 degrees to the femoral axis - think about the femur really - and we found others, it was right around more at 70 degrees to the femur. We also looked at how much of the medial border of the patella had a VMO attachment. Some people, it was a third and some people, it was right down to 95% of their medial border. So we, didn't set out to look at that, but it was such an interesting finding, so we then decided to take this and run with it from a research perspective. So, we then said, well, I wonder whether this relates to how active people are? So, we then did another study - and all these studies had been published - where we looked at Tegner scoring. So, Tegner scoring simply makes, is a way of scoring how sedentary or active someone is, and we'd measure the architecture again with the ultrasound. And sure enough, we found that people that were sedentary had a smaller fibre angle and a smaller amount of insertion. And people that were very athletic, had a large angle and a large insertion.

So, what was the burning question that I then had to answer? Can we take those people with a small angle and a small insertion, can we change that with exercise? Because that was the suggestion, but we had no proof. And so, we did another study, so we took the sedentary end of the spectrum, we put them on a very basic programme to quads overload, and of course, if you're taking people who are sedentary and weaker, it's easier to overload the muscle to light fatigue, alternate days, for six weeks. And sure enough, their muscle architecture changed.

Now look, muscle architecture research is not a new concept. The first paper was in 1955, but no one had looked it in the VMO. And of course, the VMO becomes particularly interesting and relevant because it's attaching onto the patella, which is a floating bone that will move wherever the line of pull is. So, we were able to show then that with exercise, we have a way of changing the architecture of the muscle to make it preferentially a better medial stabiliser. This is really exciting because as physios, we've known for years and years that quads work tends to help people very often with knee pain. But here lies a description of what is happening and how it is doing it.

So, we then took it further. We then said, well, we wonder if there are different types of exercises that are better? So, we did a trial which was open chain versus closed chain, and we found the results of the two groups were the same. We then did another study where we looked at closed kinetic chain exercises versus closed kinetic chain with electrical stimulation and the group that had the electrical stimulation in addition had the better result. I then wanted to know what happened more long-term, so we then did a study where one group stopped, one group carried on till 12 weeks, and the third group did - after six weeks - did two exercises twice a week. And the results were very interesting. The group that stopped saw a slight reversal of their architecture, the group that carried on to 12 weeks had a little bit more gain but not as much, and the group - and this is perhaps the most interesting message from this study - that did two exercises twice a week managed to hold their architecture change.

So, how does this work? So, in essence, when you hypertrophy a muscle, you don't get more muscle fibres, the number of muscle fibres is set, but what happens is the diameter of the muscle fibres changes. So, they become fatter and as they become fatter, they push the neighbouring fibre around and change that fibre angle, that angle of pennation. And in fact, an interesting fact for you, osteoarchaeologists look at amount of, evidence of amounts of muscle attachment onto muscles to look at how active ancient civilisations were. So, in our case, as the muscle hypertrophied, it spread down the medial border of the patella and had a bigger origin, and this is what the osteoarchaeologists are looking at with other muscle groups to see how active these civilisations were. So really very, very interesting.

So, we can offer up a better quadriceps, a better VMO and I'm sure that those of you that are working with patients will be able to picture those patients who have had a fracture, or surgery, or trauma, and have almost like a hollow appearance distally at their distal medial quads and that's because that's where those fibres have become more vertical and left this sort of gap. But we can, of course, as I've been saying, we can reverse this.

Exercises

So, we're moving away from the concept of firing the VMO in isolation because we can't. Yes, we don't want to drive delay, so we don't want to exercise, ideally, in the presence of swelling and/or much pain. A tiny bit of discomfort I think we run with, but I say to my patients, no more than about a three out of 10. Not because I'm worried about harming them, but because I think I will be ineffectual.

So, we've got to take the muscle to fatigue alternate days, and we have to do that to create that hypertrophy, to give that architecture change. Now, many of the patients, and in fact, many clinicians say, but the problem is everything I try and do is painful. So, this is where an understanding of knee angles and exercise is very helpful.

So, this has been well evidenced by Steinkamp's work. So, if we take the concept of closed chain now - so squats, lunges, leg press - between zero degrees flexion and 50 degrees flexion, yes, the patellofemoral contact load goes up. Of course, if I stand up straight and I start squatting down, I will feel that that goes up. But what happens after 50 degrees is that accelerates, and the graph does this. So, if we feel more pressure, we'll get more and more and more and this is why the patients don't generally like deep squats and lunges. So, what I say is let's stay in, particularly in the earlier parts of rehabbing, that zero to 50, but load them up. So, take the humble squat. I might start with the double leg wall squat to 45 degrees if they're weak and sore. Then I might bring them on to majority one leg, perhaps put the other foot on a ball, and I will hold it statically. And then I might increase the length of the hold, so I might do four lots of a minute with 70% of the weight on one leg, but only at about 45 degrees.

Then we might come away from the wall and we might do a double leg squat, but with some weight on a barbell or dumbbells, but again, only to about 45 degrees. Then I might stick with that, but I might do it on a BOSU or something that's slightly unstable under foot. So, what we're doing is we're progressing, we're progressing, but I'm not progressing by going deeper, banging up and down into deep flexion, which is much more likely to cause irritation. And we can apply that to the leg press, we could do isometrics, but in our range between zero and 50, apply it to squat, we can even apply it to a lunge. We're just not going to go too deep until they're really getting quite nice and strong and then we can edge into the deeper ranges when hopefully they've got the resilience, the low tolerance, and they're not going to get as sore.

And then we need to think about open chain because the graph is different for open chain. So, open chain between 90 and 45, the load increases but slowly. So, in essence, it's the other way around. Then when we go from 45 degrees to zero, think about a leg extension machine, in that range, the load really escalates. So, guess what I'm going to suggest? Yup. I'm going to suggest if you do some open chain, whether it's without TheraBand, or just seated, or with some TheraBand, or on an open chain leg extension machine, then I'm going to suggest in those earlier stages working between 90 and 45.

And, of course, we can do closed chain between zero and 45 and open chain between 90 and 45, so we're getting it to work throughout the whole range, but in different ways that are more likely for you to be able to load it up hard enough to get that fatigue. Because if you don't get to the fatigue and you don't get the recovery, you won't get the hypertrophy. So, we're looking at something like four sets of eight reps to fatigue, alternate days. And once we've got the architecture change, then we might want to move that over to more endurance bias, so we get endurance capabilities as well and that slow oxidative function. So, we might switch then to more high reps, three or four sets of 20.

And ultimately, of course, we want to work synergistically with glutes so that we get nice limb control when it is good quality movement and then always, always keeping an eye on their long-term goal. So, if they want to go back to badminton, can we start incorporating some badminton-type movements and shadowing, or actually, is it football? What is it? And keeping an eye on working towards that goal that's specific to that patient is always so key.

Okay. So, if we think about quads, the message is look out for pain and/or swelling cause that's a big clue that probably the quads, the VMO are involved in this. Don't think about VMO exercises. Just think about quads exercises. If we're doing quads exercises, we're going to be working the VMO. Okay. Don't do painful exercises. So, with respect to that as well, I think if they're very sore, think about timing the exercises after pain relief. Maybe even icing beforehand. Loro's work showed that in post-surgical patients that ice first and then do their quads work was better in terms of their EMG firing, they got better recruitment. So, time of day, they might not be very sore in the morning. Can we do their quads work then? And if they are, really are that sore that they just cannot effectively exercise to fatigue then it absolutely is worth looking at blood flow restriction training, which is a way of fatiguing the muscle quicker so that we don't get so much load on the joint, but we still get that fatigue on the muscle.

Conclusion

So, let's aspire to get this fantastic architecture back in the muscle. It's great to see this work really giving us an evidence underpinning physiologically what we do when we do our quads work and make sure that you're bespoke to the patients so that you're not just giving out the same old quads' exercises. You're thinking about what makes this patient sore, what they can tolerate, ranges, load, dosage. So, sets, reps, speed of which they're doing them. Have they got the right amount of time and attention? Think about all these things. Have they had their adequate rest days? Are they too keen and they're actually doing their exercises every day? Factor in all these elements to your quadriceps exercise prescription and then I think you'll find that whether you're doing shallow squats, shallow lunges, or maybe you're doing a reverse step down, it's a lovely way of getting some eccentric function into the quads without too much patellar load. What is it this person needs? Make it bespoke, think it through, and then you're likely to get the patient on board, get effective strength work that gives you the architecture change that then hopefully provides that dynamic stability that we're after at the patellofemoral joint.

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