Q&A: Why Does My Leg Flick Out When I Run?

In this article, I’m going to be answering a common question about why we sometimes see a runner’s leg flick out to the side when running.

Thanks to Lucy for emailing with her question!

If this is something you’ve noticed in your own running gait, then please do read on…

Question From Lucy

When I run my right leg flicks out to the right so if you think from the back as my heel comes up behind me on the left leg it’s more or less in line with my hamstring, but on the right leg when my heel comes up behind me it flicks to the right hand side.

My knees always seem to collapse inwards too if that’s related and the more tired I get the more that happens!

I always seem to have a niggle in one place or another on the right side so wondered if it was anything to do with that?

What, if anything can I do about this?

Fixing the Leg Flick

Hi Lucy, thanks for the question. You’re certainly not the only runner with a noticeable ‘flick’ on one leg or both – it’s a common trait I see in athletes of all types.

Jeptoo is an excellent example of a runner who performs at the highest level despite what could be viewed as various biomechanical flaws in her running gait.

As the heel comes up behind and under the body when running, I’d like the foot to come through inline with the leg, when observed from behind.

Some runners, however, flick the foot outwards (as you describe), some flick the foot inwards towards the midline of the body.

Clearly, neither of these two flicking actions are what we want to see in a runner’s ideal form. Such a flick can be indicative of a number of different underlying flaws – often around the hips.

The following comments should be taken with the major caveat that I haven’t seen you run! Thus I’m talking in general terms based on what your question tells me…

Your question involves two key phrases which I feel are probably linked:

…but on the right leg when my heel comes up behind me it flicks to the right hand side.

My knees always seem to collapse inwards too…

Both the ‘flick out’ when the limb is swinging, and the ‘collapse inwards’ when the limb is in contact with the ground potentially point to the same dysfunctional factor at the hip: poor control of internal rotation and adduction.

I suggest you’d most likely benefit from targeted strengthening and control exercises working the external rotators and abductors of the hip, particularly Glute Medius.

Here’s a link to receive a useful downloadable resource to help you with your running form:

Fix Your Running Technique >>
Free Training Guide [PDF]

As I said, there are a number of other possible causes – but I’d need to see you face-to-face to look at your running to be able to comment further!

Here are a couple of simple exercises to try

Read Next >>
How to Engage Your Glutes Before Running
Last updated on November 1st, 2021.


  1. Hi James,

    Would tightness or weakness in outer or inner hamstrings also cause this? Could it be that Lucy that the outside hamstrings are stronger thus want to do all the work thus kicking out the foot?


  2. Hi James,

    When my 7 YO daughter runs her legs flick out to the sides. At birth, she was diagnosed with hip dysplasia and was put in a hip spiker for a period of 12 weeks. The diagnosis only came from the fact that I had Perthes disease when young and I went through a more invasive and long period of treatment requiring a hip replacement, so I asked for tests to be done.

    My question is, is the flicking of the legs treatable, and what would be the treatment or exercises involved.

    Great website.