May The (Knee) Forces be With You

Picture from Hart et al, 2022

We were discussing the knee joint in our clinic this past week. Meaning ALL the conditions that can cause pain in the knee. Patellofemoral joint pain, patella tendinopathy, MCL, ACL injuries, fat pad irritation, torn meniscus etc. 

In order to understand knee joint injuries, we need to know what can increase load or amplify forces in the knee joint. An increase in joint forces can increase symptoms when one has patellofemoral pain (PFP) so it will be most helpful to know what activities may influence patellofemoral joint reaction forces (PFJRF).

Picture from Dr JT Andrish

So happened that I came across an article explaining how PFJRF compares across different activities and interventions.

intercondylar notch

PFJRF is created by tension (or forces) in the quadriceps and patella tendon which moves the patella into the intercondylar (pictured above) surface (of the femur). It can increase due to greater quadriceps muscle force or when there is an increase in knee flexion (or knee bending).

The article (systematic review) examined PFJFR in daily activities, exercises, interventions (treatment). It also compares healthy individuals to those with PFP or osteoarthritis (OA).

A total of 71 articles were included in the systematic review. Approximate PFJRF for healthy individuals during various activities are pictured below where BW = body weight. 

Knee joint forces in healthy individuals

As you can see, activities that involve greater knee flexion or greater external load resulted in higher PFJRF. For example a deep squat with a heavy weight.

An increase in knee flexion can increase the contact area (in the intercondylar area) and may therefore reduce patellofemoral contact pressure. The authors felt this would be the case in a knee that is "normally aligned". However, certain movements during loading such as increased hip adduction (pictured below) and/ or internal rotation may reduce contact area and increase contact pressure.

Increase in hip adduction in picture A

The authors reported that there were no discernible differences in peak PFJRF during daily activities between healthy individuals and those with PFP/ OA.

There are 3 options if you have knee pain and we need to reduce PFJRF. Reduce knee flexion/ bending during loading. Reduce external load. Reduce hip adduction/ internal rotation during loading.

So if you are weight training by doing a squat and your knee hurts. You can squat less (70-80 degrees) and / or using a lighter weight. Preferably with less hip adduction too. 

In running we can apply this by increasing step rate/ cadence to reduce patellofemoral load. Smaller, quicker steps reduces knee flexion and hip adduction during the stance phase of running. Or better still make your gluteus medius, hamstrings and calf muscle a lot stronger.

Note that the goal is to reduce load only when symptoms are present and the knee is irritated. You can gradually increase load again when able. For other clinicians and physiotherapists reading this, a progressive approach is needed and utimately it will be your patient symptoms and goals that will guide you.

Do note that the exact link between PFJRF and knee pain is complex and the lack of difference between those healthy inviduals without knee pain and those with PFP/ OA draws attention to this. 

The authors also mentioned that when articular cartilage is underloaded (not enough load), it may be an issue too. 

Reference

Hart HF, Patterson BE, Crossley KM et al (2022). May The Force Be With You: Understanding How Patellofemoral Joint Reaction Force Compares Across Different Activities And Physical Interventions- A Systematic Review And Meta-Analysis. BJSM. 56: 521-530. DOI: 10.1136/bjsports-2021-104686

Can A Bit Of Tape Rotate Leg Bones?

Unlike others in the picture above who are skeptical and think that leg bones cannot be rotated with "a bit of tape" in 2022,  I remain open to finding out how to treat our patients with knee pain. 

Just because I cannot ride a unicycle does not mean others cannot. Similarly if the author above cannot rotate his / her patient's leg with "a bit of tape" does not mean others can't.

We do see many patients in our clinics presenting with knee pain. Even though we have very good results treating these cases, I am always on the look out on how to get these patients with knee pain better quicker. Especially those who run.

In our clinics, we almost never tape the patient's knee, especially if the cause of their knee pain is coming from elsewhere. In fact, we do not even use rigid sports tape when we do tape the patient's knee.

Using Kinesio tape compared to using rigid sports tapes to do McConnell taping, (first published in 'Physiotherapy' journal in 1986 by Australian physiotherapist Jenny McConnell) definitely produces a superior result.  

So I was really intrigued when I saw a paper that investigated the effects of using rigid sports tape for tibial internal rotation taping (IRT) and external rotation taping (ERT) done on subjects with patellofemoral pain syndrome (knee pain) during three functional tests. During double leg squat, single leg squat and maximum isometric thigh muscle contraction.

Internal rotation taping

The researchers found that compared to no taping, both IRT and ERT significantly reduced pain during the three tests, especially for those with higher pain levels initially.

External rotation taping

ERT was found to be more effective than IRT. Why? The authors did not provide any suggestions. My thoughts are that when you externally rotate your tibial (shin bone), you can activate your gluteus medius better. Remember, one of our most popular posts shows that the cause of patients' knee pain is usually coming from the hip.

To see if the two taping techniques work, let me try the ERT and IRT techniques on my colleagues in our clinics first before I unleash them on our patients. Bear in mind we still want to treat the cause of the problem and not just the pain itself.

Reference

Deng F, Adams R, Pranata A et al (2022). Tibial Internal And External Rotation Taping For Improving Pain In Patients With Patellofemoral Pain Syndrome. J Sci Med Sp. DOI: 10/1016/jsams.202204.003

*thanks to Byron and Megan for helping me with the photos

Arch Supports And Iliotibial Band (ITB) Pain

A patient came in this week after being diagnosed with Iliotibial band (ITB) syndrome. The outer part of his right knee would hurt badly after running about 1.5 km. After stopping to walk, he would be able to run for a few minutes before having to stop again. 

He had been running 4-5x each week, clocking about 50 km weekly. He had just seen a sports doctor who first referred him to a podiatrist to get orthotics as he 'pronated' badly.

After getting his orthotics, he 'pronated' less according to the prodiatrist who filmed him while running on a treadmill. But, alas, his ITB/ knee pain didn't change. Since I'd treated a fellow runner he knew, he came to see me, hoping I could help him run pain free.

The ITB starts from the TFL

I've written previously about the ITB and you can read more about it here (anatomy) and here. If you look at the picture above, you can see it starts from Tensor Fascia Lata (TFL) muscle and runs down the outer thigh before finishing just at the outer part of the knee (picture below). This is usually where runners experience a sharp pain.

Also know as iliotibial tract (bottom R of pic)

Studies show that when the hip rotates medially or drop inwards, a strain is placed on the ITB . This also causes the tibia (or shin bone) to rotate inwards causing the foot to pronate (or ankle eversion). 

Researchers have attempted to correct this by changing ankle pronation to see if this might relieve the strain on the ITB.

In this published paper, 30 runners (15 males, 15 females) with no ITB insertion pain were prescribed orthotic wedges to put into their own running shoes. The wedges were 7 degrees lateral, 3 degrees lateral, no wedges, 7 degrees medial and 3 degrees medial. A total of five running trials were done.

The runners were analyzed by video motion analysis while running at their self selected running pace to calculate motion forces and ITB strain.

The orthotic wedges significantly changed ankle eversion (or pronation) angles compared to no wedges. However, the strain rates did not differ between conditions. There was no change in knee joint angles and tibial rotation under all orthotic wedge conditions. 

The researchers concluded that orthotic wedges may not change forces acting on the ITB, even though they altered foot pronation while female runners had greater strain forces acting on their ITB's potentially due to increased internal hip rotation.

It is interesting to note that the female runners demonstrated significantly greater peak ITB strain and strain rates compared to the male runners, potentially due to increased hip internal rotation (because of wider hips and pelvises for child bearing purposes). I have written at length before that for female runners, their knee pain is coming from their hips. Always treat the cause of the problem. Do not treat the pain alone.

Take home message is that even though orthotic wedges can correct your foot's pronation, it may not alter forces acting on your ITB. This means that your knee pain may not get better using orthotic wedges.

Of course any one reading this may say that these off the shelf orthotic wedges are not customized and that the subjects were all wearing different running shoes. Personally I feel that the different shoes are not an issue as these orthotic wedges used in the study did significantly change ankle pronation so they did what they were supposed to do. 

Would this then be fair to say that using orthotics to change ankle pronation or eversion angles does not seem to benefit those with ITB pain at the knee? Perhaps any podiatrists reading this would like to comment.

Reference

Day EM and Gillette JC (2019). Acute Effects Of Wedge Orthoses And Sex On Illotibial Band Strain During Overground Running In Nonfatiguing Conditions. JOSPT. 49(10): 743-750/ DOI: 10.2519/jospt.2019.8837

ITB attachments at the knee

Is Your Running Style Causing Your Running Injury?

How's my running gait?

I saw a patient yesterday who was training for the upcoming Singapore marathon. He started having knee and heel pain after doing a long run of 22 km over the weekend. Upon assessment, he definitely demonstrated a greater contralateral (or opposite) pelvic drop (CPD), indicating Gluteus Medius muscle weakness.

Picture A- Injured runner with CPD and right hip adduction 

Last week we discussed whether doing clam shell exercises was still relevant for someone with Gluteus Medius muscle weakness. Turn's out that this week's post is related to that.

The referenced study (Bramah et al, 2018) investigated and identified certain faulty running gait patterns that contribute to running injuries. In all, 108 runners were studied, including 72 injured runners and 36 healthy runners in the control group matched for age, height and weight.

None of the injured runners received any prior treatment for their injury. Those with an increase with more than 30 percent in training volume were also excluded from the study. The control group of runners ran at least 30 miles (or 48 km) a week.

The injuries the injured runners had were patella femoral pain (PFP), Iliotibial Band Syndrome (ITBS), Medial Tibial Stress Syndrome (MTSS or shin splints) and Achilles Tendinopathy (AT). The injuries were selected as they are most prevalent among runners.

All the injured runners showed a greater contralateral (or opposite) pelvic drop (CPD), demonstrating Gluteus Medius muscle weakness. They had a more extended knee and dorsiflexed ankle (heel striking) at initial contact and a forward trunk lean at the midstance phase of running. These patterns were consistent across each of the four injured groups.

Contralateral pelvic drop

CPD was found to be the most important variable predicting whether the study participants were healthy or injured. For every 1 degree increase in pelvic drop, there was a 80 percent increase in the odds of getting injured.

Injured runner (L) heel striking, forward trunk lean vs normal

Those who had more knee extension makes the patella (kneecap) more vulnerable to lateral tilting and displacement. This may affect knee joint contact areas and increase stress when the foot strikes the ground. If a runner heel strikes with the knee extended, their center of mass is further away from their foot. This leads to an increase in knee joint loading and a increase "braking" forces (imagine applying brakes on while you're running).

Those with a forward trunk lean may have weakness around the back and gluteal muscles as shown by previous studies. The injured runners with PFP and ITB problems had more hip adduction than other runners. More female runners were also found to more hip adduction compared to male runners.

So make sure your Gluteus Medius muscles are strong enough so that you will be less likely to have a running injury.


References

Bramah C, Preece SJ Nimh G et al (2018). Is There A Pathological Gait Associated With Common Soft Tissue Running Injuries? AJSM. 46(12): 3023-3031. DOI: 10.1177/0363546518793657

Lessi GC, Dos Santos AF et al (2017). Effects Of Fatigue On Lower Limb, Pelvis And Trunk Kinematics And Muscle Activation. J Electrom Kinesiol. 32: 9-14

Fat Pad Most Painful In The Knee?

I had a patient who came to our clinic recently complaining that his MRI showed that his patella (knee cap) cartilage had "worn out" completely but he didn't have any pain prior to that. He had actually gone to do his MRI under his doctor's insistence for investigating something else.

His  MRI results was like in his words "opening a can of worms" telling him what's wrong with his knees and perhaps that's why he started having pain after that.

After his ranting, I had to explain very thoroughly about the structures in our knees that cause the most pain. The information I gave him was derived from an article published quite a while ago in the American Journal of Sports Medicine but still very relevant today.

The doctors in that study came up with a simple method to document the various sensations felt inside a single subject's knees one week apart. Right knee first, followed by the left a week later. (Note that the subject had no prior knee pain).

They would arthroscopically poke/ palpate (using a specially built spring loaded device) different structures inside the knee while video recording the procedure and record what the subject's response was. Force used was between 0 to 500 grams. All this done without intra articular anesthesia. Ouch! That must really hurt.

The doctors only injected local anesthesia at the portal site (incision). The first author inspected both knees arthroscopically. He asked the patient when he poked at different structures and graded the sensation as follows (0) no sensation; (1) was non painful awareness; (2) slight discomfort; (3) moderate discomfort and (4) severe pain. This was done with with a modifier of either accurate spatial localization (A) or poor spatial localization (B).

Ready for the results? They were exactly the same for both knees. Even though it was done one week apart.

Palpation of the patellar articular cartilage in the three under surfaces (central ridge, medial and lateral facets) resulted in no sensation, or a 0 score, even with a strongest force of 500 grams. Palpation of the odd facets elicited a score of 1B. Asymptomatic grade II or III chondromalacia (wearing out) of the central ridge was identified on both patellas of the subject!

Palpation of the articular cartilage surfaces of the femoral condyles, trochlea, and tibial plateaus at 500 g of force universally produced a sensation of 1B to 2B.

The sensation from the meniscus ranged from 1B on the inner rim of the meniscus to to 3B near the capsular margin.

Sensation from the  cruciate liagaments (Anterior, posterior cruciate ligaments) range from 1-2B in the mid-portion of the ligaments and 3-4B at the insertion sites.

Palpation of the suprapatellar pouch, capsule, and the medial and lateral retinacula produced a score of 3A to 4A (moderate to severe localized pain) at relatively low levels of force (about 100 g).

The most painful structures were the anterior synovium of the knee, the fat pad and the joint capsule - 4A.

The human knee can be very complex, especially our patellofemoral joint (patella and the femur). The three asymnetrical surfaces on the underside of the patella (or knee cap) has to work together with the femur as it accepts, transfers and dissipates loads between the bones.

We know from previous research that various structures in the knee send neurosensory signals (or messages) to the brain. It is theses signals that result in us feeling pain.

Even though my patient's patella cartilage had worn out (just like the subject) there shouldn't be any pain there as articular cartilage doesn't have any nerve supply. No nerve endings means it is unable to detect pain.

Even the ACL and meniscus wasn't really that sensitive to the poking. This observation may provide an explanation for the often poor localization of structural damage that many patients experience with a cruciate ligament or meniscal injury.

Now you know, worn out articular cartilage doesn't cause you pain. The pain you have is likely to come from other structures. And you definitely don't need to ingest any glucosamine too.


Reference

SF Dye, GL Vaupel and CC Dye (1998). Conscious Neurosensory Mapping Of The Internal Structures Of The Human Knee Without Intraarticular Anesthesia. AM J Sp Med. 26(6): 773-777. DOI: 10.1177/03635465980260060601.

black and white version

Don't Always Believe What You Read

Below is an article from yesterday's Financial Times. John Connors, the quoted podiatrist suggests wearing "maximalist" running shoes like him "as we get older, we are the ones who need the most shock absorption underneath our shoes."

Well, my last patient yesterday started having knee pain after he started wearing Hokas. This patient of mine has done the grand daddy of triathlons, the Hawaii Ironman triathlon and has also run the Gobi March race, a 250 km desert race, before you think my patient is a rookie runner. He too was probably "fooled" by what he read from another article about the benefits of Hokas.

My patient's Hokas

My patient's knee is a lot better after yesterday's treatment, but I think he's not going to wear his Hokas for now. Don't get me wrong, the shoe may suit some runners, but not my patient or you for that matter.

Here's the article.

Fat-soled running shoes to protect middle-aged knees

25 February 2014

The Financial Times

As I huffed and puffed down the glorious Bowen Road jogging path during my last visit to Hong Kong, I was surprised to see a line of runners approaching, wearing what appeared to be black gloves on their feet instead of shoes. These, of course, were the now famous Vibram Fivefingers, which helped start the current fad for minimalist trainers.

The idea behind minimalist athletic shoes is simple enough: the closer to running with bare feet, the better. The theory is that raising the heel above the toes causes all sorts of bad things in your feet. Christopher McDougal’s exciting book Born To Run details how Mexico’s Tarahumara Indians run 100km mountain races in leather-thonged sandals without a whimper.

Back at home base I bought a pair of minimalist trainers and took them out for a spin. Eight hours later, it felt as if someone had poked needles into my calves. For an explanation, I turned to John Connors, a New York podiatrist who advises the world’s elite long-distance runners and was physician to the US team at the London Olympics.

Dr Connors laughed and said he had been seeing an increasing number of patients who had tried to adopt minimalist running shoes. “People say to me we weren’t designed to run with trainers,” Dr Connors says. “But we were also not designed to run on concrete and macadam.”

Dr Connors says that when you run, you are hitting the ground with four times your body weight, and hard surfaces such as concrete cannot absorb the shock. So the force goes right back up your leg. “Minimalist shoes are putting more stress and strain on the Achilles tendon, and more stress on the bones of the foot and leg,” he says. “I’ve been seeing a spike in Achilles injuries because of the eccentric load being placed on the tendon.”

He believes middle-aged runners need to take special care even if they are frequent exercisers because cartilage in their knees is beginning to wear down through normal use. His solution? “Lessen the load on the knee by getting something underneath you that reduces the load.”

As if by divine intervention, a new type of running shoe has started to appear in stores in the US, Europe and parts of Asia as an antidote to the minimalist trainer craze. It is called the Hoka One One and is the brainchild of Jean-Luc Diard and Nicolas Mermoud, former executives of French sporting goods company Salomon.

Mr Diard and Mr Mermoud are ultra-marathon mountain runners and wanted a shoe that would not destroy their legs when they ran downhill, which puts more stress on the lower legs. The Hoka idea they came up with, more by trial and error than scientific theory, has between 1.5 and 2.5 times the cushioning of normal trainers, depending on the model. But because the cushioning is evenly layered along the bottom of the shoe, the Hoka’s heel is actually much more like a minimalist shoe in terms of drop to the toe.

After studying the world’s elite runners, Dr Connors says that the best way to land when running is on the mid-foot, because the body then has the ability to absorb the shock and propel the body forward. The Hokas are ideal for this because of the way the cushioning is centred on the mid-foot.

Dr Connors says that while most elite runners use traditional trainers, he now runs in Hokas because he has a torn meniscus, the shock-absorbing cartilage of his knee: “As we get older, we are the ones who need the most shock absorption underneath our shoes.”

Running Injuries Linked To Your Footstrike

Photo by Jordan Shakeshaft from flickr

I wrote earlier that the minimalist/ barefoot inspired type running shoes sales were declining, however researchers seem to be very keen on finding how they affect running still. To put it simply, researchers are very interested to find out if barefoot running, minimalist shoes or how you land (forefoot, mid or rear) can reduce injuries.

A group of South African researchers specifically studied how barefoot running (or forefoot striking) affects five common running injuries.

Bear in mind that many researchers and runners alike tend to assume "barefoot running" and running with forefoot/ midfoot strike as similar although some studies have shown differences.

Well, here are the main points on the five common running injuries. Regarding shin splints/ tibial stress fractures injuries are decreased by barefoot running although runners have to be extra careful with transition time from their previous more cushioned shoes.

Increased incidences of metatarsal (or your foot) stress fractures with barefoot running. I've seen some of our patients with metatarsal fractures after switching to Vibram Five Fingers.

As I've written earlier before, good news if you have knee pain as it may be reduced by barefoot running, but not so good news if you have Achilles tendon injuries as it may be increased with barefoot running.

For those of you with plantar fasciitis, barefoot running can reduce this if you gradually and correctly transition from your cushioned running shoes.

Well, as you can see, nothing is foolproof yet with barefoot running. What the researchers were sure was that bad training practices like training too much too soon, running too fast and hard are the major causes of running injuries. And my favourite, they mentioned that good (i.e. correct) running technique may be more important than shoe selection.

Reference
Tam N, Wilson JLA, Noakes TD and Tucker R. (2013). Barefoot Running: An Evaluation Of Current Hypothesis, Future Research And Clinical Applications. BJSM. doi:10.1136/bjsports-2013-092404.

Comparing Running Barefoot Versus Nike Free, Lunaracer And Own Running Shoes

Nike Free 3.0

This recently published article in the British Journal of Sports Medicine caught my eye as it compared highly trained runners running in four conditions namely, barefoot, running in a Nike Free 3.0, Nike Lunaracer 2 and their own running shoe. Well, good news if you have knee pain, but not so good news if you have ankle, foot, Achilles or calf pain.

22 highly trained, high-level runners (average 10km time of 33 mins) were chosen by the researchers. Each were given a pair each of Nike Free 3.0, Nike Lunaracer 2 and they had 10 days to run in them and barefoot to get used to them. In addition they also ran in their regular running shoes (on average 125-140 g heavier than the 2 Nike shoes given).

The runners were filmed and their running gait measured using 8 force plates. After a warm up, they did 10 running trials in each of the four conditions (running barefoot, Free, Lunaracer, own running shoe). Their average speed was fast, at 4.48 m/s (or 6 min miles).

And the results? Well, the study showed that running barefoot ia a lot different than running in shoes, but the different shoes did not differ much.

One real difference though was that the runners tended to have a shorter, quicker stride in the Nike Frees and Lunaracers compared to their own regular shoes (average cadence of 183.9 steps/ min versus 181.3).

Key differences between barefoot running versus running in shoes were numerous. Barefoot running elicited a shorter stride length than all shod conditions. There was also higher cadence than all shod conditions (average 187.7 steps/ min). Flatter foot placement at contact and greater ankle plantarflexion at toe off were also observed.

There were also less work done at the knee (24% less when barefoot compared to own running shoe). There was greater joint movements and more work done at the ankle though.

The authors summarized by adding that knee and ankle mechanics were different when running barefoot compared to all shod conditions, including minimalist shoes. Meaning that the minimalist shoe cannot entirely replicate the mechanics of running barefoot.

What does this all mean for you, the runner? Well, this article confirms that running barefoot mechanics are different compared to running in a well cushioned shoe. Running barefoot tends to reduce work done in your knees, but increase work done in your ankles.This means that barefoot running will help those with knee pain but may stress your foot, calf, Achilles and ankle more. So good for those with knee pain but not so great for those with ankle, calf, foot, Achilles pain.

The researchers also acknowledged that the Nike Free may not be really considered a minimalist shoe (given its elevated heel and cushioning available). Wearing a more "minimalist" shoe like the Vibram Five Fingers may be closer at replicating barefoot running although even ultra minimal running shoes will not be be a perfect replication to running without footwear.

Lesson here is that wearing minimalist shoes may not instantly replicate barefoot running. I personally feel your running form is more important. Please also see this and this.

Email me if you want a copy of the article.

Reference

Bonacci A, Saunders PU et al (2013). Running In A Minimalist And Lightweight Shoe Ia Not The Same As Running Barefoot: A Biomechanical Study. BJSM. 47: p 387-392.

*Picture from Nike.com