Effects of two gait retraining programs on pain, function, and lower limb kinematics in runners with patellofemoral pain: A randomized controlled trial

Two pages on PainSci cite Júnior 2024: 1. The Complete Guide to Patellofemoral Pain Syndrome 2. Study: Softer, quicker running improves patellofemoral pain 

PainSci commentary on Júnior 2024: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

This small but good test of two gait retraining programs produced truly fine results for patellofemoral pain, both from running softer or dialing up cadence. And for a dorky bonus prize? These benefits came without a flicker of change in kinematics — which tickles my bias. News that I can feel good and smug about is not exactly the usual fare around here. I’ve got chills!

Brazilian researchers de Souza Júnior et al. recruited thirty runners and divvied them up into a three groups — so not huge — one focusing on easing impact, the other on a quicker cadence, while the third served as a control group. The runners did eight gait-retraining runs over two weeks, ramping up from 15 to 30 minutes, and they were evaluated for pain, function, and the details of their lower limb movement right before, right after, and then again after another six months of running.

Impact was eased with forefoot running and — this is cool — by working with a real-time display of how hard they were hitting the treadmill, from an accelerometer on the shin. It’s a lot easier to run softer when you can see the literal impact of every step.

The cadence group wasn’t quite as cool, but they still got a gadget: a metronome! They used that to increase their cadence by about 10%. Running cadence and speed are related, but they’re not the same thing. Cadence is your rhythm, how fast you put your feet down, like the beats per minute in a song — hence the metronome.

How fast you go depends on how big those steps are. You could have a high cadence with short strides and not be moving very fast, or a lower cadence with longer strides and be cruising along pretty quickly. So changing one doesn't exactly mean changing the other, but they do affect each other quite a bit, and most runners naturally increase both at the same time in the short term — e.g. a sprint naturally needs both, and long haul running tends to reduce both. The highest cadences require shorter steps, because a longer step just takes longer, and therefore also less hinging of the knee … which is one obvious reason why higher cadence may have been helpful.

“How hard are you hitting yourself?” Runners were shown exactly how hard they were hitting themselves with the ground with a display powered by a shin-mounted accelerometer. By de Souza Júnior et al., CC BY 4.0 DEED.

Less pain without kinematics changes

Pain and knee function improved more in both kinds of gait-tinkerers than the control-group runners — but, notably, without any change to how the lower limb was moving. This flies directly in the face of the almost unanimous assumption in this business that changes in pain and function are the result of improvements in biomechanics. But that’s not what we see here. What we see instead is real change in pain and function … without the slightest signal in the kinematics. The authors write:

“two-weeks of using a strategy that does not address lower limbs kinematics directly may not be sufficient to modify these variables in individuals with patellofemoral pain.”

Mayhaps not. And maybe those variables don’t really matter at all. 🤯 And the authors do acknowledge this.

Decent effect size? Check!

But just how “real” were those pain and function changes? The changes were happy changes, but… how happy? Normally I would expect to see underwhelming results, and probably overstated based on “statistical significance.” But no!

Júnior et al report an equally “large” reduction in running pain with both groups, while function improvements were “moderate.” With a larger sample size, it would be kind of a big deal. As it is, it’s just legitimately promising.

There are some problems, of course

The perfect scientific trial has never been done. There are always concerns, and in this case there are two particularly obvious problems:

1. The strong effect on running pain could be a research artifact caused by a lack of blinding.
2. Regardless, pain when not running barely changed at all.

I explore those concerns in more detail in my book about patellofemoral pain … but still basically conclude that it’s a good-news study.

~ Paul Ingraham

original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:

• Classical Conditioning Fails to Elicit Allodynia in an Experimental Study with Healthy Humans. Madden 2017 Pain Med.
• Topical glyceryl trinitrate (GTN) and eccentric exercises in the treatment of mid-portion achilles tendinopathy (the NEAT trial): a randomised double-blind placebo-controlled trial. Kirwan 2024 Br J Sports Med.
• Placebo analgesia in physical and psychological interventions: Systematic review and meta-analysis of three-armed trials. Hohenschurz-Schmidt 2024 Eur J Pain.
• Recovery trajectories in common musculoskeletal complaints by diagnosis contra prognostic phenotypes. Aasdahl 2021 BMC Musculoskelet Disord.
• Cannabidiol (CBD) products for pain: ineffective, expensive, and with potential harms. Moore 2023 J Pain.