This is Part 1 and will go through 3 biomechanical faults that can lead to knee valgus, which is an excessive inward leaning or rotation of the knee. In Part 2 I’ll describe ways to address each of the faults.
Knee valgus when running, changing direction and landing from jumps is often looked at as a risk for knee injury such as ligament sprain (ACL and MCL in particular), meniscal tears, ITB syndrome, patellofemoral syndrome, osteoarthritis and similar. Some lead to traumatic incidents while others have a gradual, insidious onset with pain only appearing potentially months or years down the line. Pain doesn’t have to be located only in the knee – often the hip will be the one to cry out instead. (In saying all that, you can have knee valgus tendencies and never have pain; this will happen if the stress is lower than the body’s threshold for pain and/or it is able to repair the stress on the tissue in time before your next bout of exercise.)
It’s been advised to clinicians for years to focus on glute medius strengthening as a primary cause of concern, prescribing basic exercsies like clam shells or crab walks with a band as a fix. Though the gluteal muscles at the pelvis play an important role in knee control1, neuromuscular control is more reactive than isolated drills like clams and crab walks can simulate. Knee valgus occurs during relatively high speed movements and therefore an athlete’s competency has to stretch to this level. On top of this, the hip is not the only place an athlete can lose control; the trunk and foot/ankle can be players too. A good assessment is going to help you start off on the right path.
If you’d like to test yourself, a single leg squat test has been shown to correlate with likely dynamic knee valgus.2 You need only go down about halfway and come back up again. Keep your hands on your hips. A ‘failed’ test is if the knee travels excessively inwards, your hands come off your hips, your trunk sways excessively or you lose balance altogether. Record yourself doing a few reps and watch it back.
3 Possible Causes
This list doesn’t necessarily paint the full picture for everyone. Your injury history could lead to more findings and ‘kinks in the chain’. However, these are common enough areas to observe a sub-optimal movement strategy leading to knee valgus.
1. Excessive Foot Pronation
When landing, some people end up with all of their weight on the inside edge of their feet rather than spreading it across from the outside edge to the inside. Often you will be able to see this from behind as the outer edge is slightly elevated off the floor. If judging yourself in the single leg squat, you might notice that you can’t feel the floor with the outer side of your foot.
It’s quite apparent in this former client’s running.
Another clue that knee valgus is happening while she runs is the way her knees literally touch each other! This is also why the issue will be commonly referred to as ‘knock knees’.
2. Avoiding Ankle Dorsiflexion
The next potential cause is just a small step up the chain into the ankle. Here when I say ankle dorsiflexion what I’m referring to is how the shin moves forward over the foot. Usually the knee will track over the big toe and second toe. Sometimes people will turn their foot outwards to avoid this position. (Though this can also be linked to hip retroversion.) Another strategy would be to twist the shin inwards and go aggressively through foot pronation in order to get your body moving forward over the foot.
People who are using this strategy usually have highly restricted ankle dorsiflexion range of motion. Though the problem was with the ankle in the above photo, this client actually had hip pain. Treating the hip alone would do very little to fix the issue long term.
3. Trendelenburg Gait – Excessive Hip Drift
This final reason leads us back to the glutes not doing their job well enough. The pelvis should ideally be level, or only slightly slanted, when we are on one leg – as seen in the first image above. However, people whose glutes are not working enough on the pelvis in the frontal plane will see it drop:
The hip will drift outside the foot which will lead the knee to fall inside the foot instead of over it.
Those are 3 potential reasons a person may be displaying knee valgus while walking or running. In Part 2, I’ll go through some of my strategies for improving them.
- Rinaldi, Vito & Prill, Robert & Jahnke, Sonja & Zaffagnini, Stefano & Becker, Roland. (2022). The influence of gluteal muscle strength deficits on dynamic knee valgus: a scoping review. Journal of Experimental Orthopaedics. 9. 81. 10.1186/s40634-022-00513-8.
- Ugalde, V., Brockman, C., Bailowitz, Z. and Pollard, C.D. (2015), Single Leg Squat Test and Its Relationship to Dynamic Knee Valgus and Injury Risk Screening. PM&R, 7: 229-235. https://doi.org/10.1016/j.pmrj.2014.08.361