Most people have heard that during squatting they should try to keep their knees from moving in front of their toes. Then I am sure you have also heard the argument that it is indeed ok for those knees to go forward. The answer to what is right simply depends on what what you are doing and what your goals are. If you goal is to load the quadriceps and the patellar tendon more, then let that knee move forward. If you are trying to minimize load and stress on the quad and patellar tendon, keep that knee back. There is some literature on this effect, with more coming out in the recent years (Kernozek et al., 2018; Zellmer et al., 2017).
When it comes to running, there is no literature on excessive anterior knee translation that I am aware of. However, clinical experience has shown me a similar movement impairment present in many runners with patellofemoral (knee) pain. This may be due to the fact that running has a much higher impact load that squatting (depending on how much load you carry with the squat and the speed to which you move). So while individuals may be able to get away with knees forward to toes with squatting, during running athletes may not have as much leeway.
A big thank you to Ashley Bell for modeling some photos for this piece! This is a clear example of the excessive knee anterior translation. Her foot has not passed under her body yet and that knee is already forward of her toes!
RUNNING IMPAIRMENT
Excessive knee anterior translation involves the knee moving too far past the toes during the loading response (landing - very rare) and midstance phases of gait. Typically this movement impairment occurs during the middle of stance phase (midstance) when the foot is traveling either directly under or just behind the center of mass (trunk or pelvis usually).
This may also be observed as excessive knee flexion. Typical knee flexion during the stance phases of gait should be between 40-45 degrees (Novacheck, 1998). Knee flexion is needed and important for appropriate quadriceps eccentric loading during landing and into midstance to help with shock absorption. Excessive knee flexion can mean that an individual is using their quadriceps and knee joint excessively.
Approximately 53 degrees of knee flexion, excessive of the normal 40-45 degrees (when on flat ground).
ASSOCIATED INJURIES
With excessive load on the patellofemoral joint, it is not unexpected that some of the major associated injuries include the patellofemoral joint and/or patellar tendon. With excessive anterior translation during squatting or lunging causing excessive load on the patellar tendon and patellofemoral complex (Kernozek et al., 2018; Zellmer et al., 2017), increasing the load with running may only further increase the risk for injury at these sites.
Image from www.bridge38physiotherapy.co.uk
Both excessive anterior translation of the knee as well as excessive ankle dorsiflexion. This can lead to excessive load on the patellar tendon, patellofemoral complex AND the achilles tendon.
The achilles is another area that be prone to injury with this dysfunction due to excessive ankle dorsiflexion (bend of the ankle). The excessive "stretch" or "strain" actually increases compression of the tendon, which may have a strong influence on achilles tendinopathy (Bogaerts et al., 2016). Although not researched, one could extrapolate that with increased strain on the achilles tendon, the myofascial connection to the plantar fascia could also put an individual with the above movement impairment at risk for plantar fasciopathy (aka plantar fasciitis).
Fairly even knee over toes with slight variation in three of the best distance runners. Some slight variation but even at the end of a half marathon at almost sub 60 min pace, the knees are relatively straight or behind the toes. Bekele may be borderline, which may explain his history of achilles issue.
CORRECTIONS
While quadriceps weakness could definitely be a possibility, most of the time this movement impairment is associated with quadriceps overuse. People will often overuse their knee joints for loading if the muscles around other joints are weak. The culprits more often are a weak gastrocsoleus complex (calves) or a weak glutes (butt). The gastrocsoleus controls the forward progression of the tibia. With weak calves, there can be excessive dorsiflexion due to poor control. This excessive dorsiflexion may contribute to the excessive anterior knee translation. Obviously the way to deal with this is to strengthen the calves. This can be a real problem for runners, who should be able to do at least 25-30 single leg calf raises in a row on each side (if not more). If single leg is too difficult, start on two legs and gently progress into single leg.
These can be performed with a bent or straight knee. If you are going to perform them with a bent knee, obviously do not let it go too far past your toes! For those wanting to increase difficulty, this can also be done on a step, but is not necessary.
A weak gluteus maximus may also be a culprit. A weak hip complex may mean a lack of loading at the hip and instead at the knee joint. This impairment may be apparent in those runners who run with an excessively flexed knee and a very upright trunk. The other issue coming from weak glutes is a lack of posterior thigh drive. Those hip extensors need to drive the thigh backwards to assist with the propulsion phase of running. If they aren't doing their job, that thigh may lag behind, leading to it being left in front, causing the foot to pass under the knee and thus you get that anterior translation. So glute work needs to be a part of your routine. Keeping those strong will also help keep that knee in a preferred spot.
There are a variety of exercises to train the glute max. Squats, Single Leg Squats, Deadlifts, Single Leg Deadlifts and more. I still really like Single Leg Bridges due to their difficulty. These can be progressed into the Single Leg Hip Thrust, which is also a favorite of mine that really gets that hip drive going.
Once you have improved your strength, the movement training needs to occur. Depending on where the athlete has had an issue, the cues I give people are either "push off the ground" (calf) or "push with your butt" (glutes). There are plenty of cues out there, but once you figure out your problem spot, you need to practice changing your movement!
The Chair of Death exercise is a great movement retraining method from Jay Dicharry. Stand in front of a chair and squat. Use the chair as feedback to keep your knees from going forward. I use this as a drill for my runners before their runs. Perform x20 before your run to work on that movement. You can also use a rod to keep your back from bending excessively to further train movement from your hips.
Hill Repeats are a great way to incorporate all those exercises into functional strength! The force forward lean increases glute activation, the hill demands hip drive and ankle plantarflexion (so increase calf strengthening). Hill Repeats are a great functional way to work on this!
This is a common but very fixable movement impairment among runners. For those that suffer knee pain or achilles issues, know your problems likely can be solved. If strengthening isn't changing things, you may still need to change your movement! Movement is one of the most important things. It is what many times separates the injured and non-injured. Excessive anterior knee translation is something many may get away with during squats, but during the increased forces with running they likely will not. Fix this issue now and keep those knees and ankles healthy!
Thanks for reading!
Dr. Matthew Klein, PT DPT OCS
Doctor of Physical Therapy
Board Certified Orthopedic Clinical Specialist
Kaiser SoCal Manual Therapy and Sport Fellow
Doctor of Physical Therapy
Board Certified Orthopedic Clinical Specialist
Kaiser SoCal Manual Therapy and Sport Fellow
***Disclaimer: As always, my views are my own. My website should not and does not serve as a replacement for seeking professional medical care. I have not evaluated you in person, am not aware of your injury history and personal biomechanics, thus am not responsible for any injury that you may incur from the performance of the above. I have not prescribed any of the above exercises to you and thus again am not responsible for any injury that may occur from the performance of the above. This website is meant for educational purposes only. If you are currently injured or concerned about an injury, please see your local physical therapist. However, if you are in the LA area, I am currently taking clients for running evaluations.
REFERENCES
1. Bogaerts, S., Desmet, H., Slagmolen, P., Peers, K. (2016). Strain mapping in the Achilles tendon - A systematic review. Journal of Biomechanics, 49(9): 1411-1419. doi: 10.101/j.jbiomech.2016.02.057
2. Fry, A., Smith, J., Schilling, B. (2003). Effect of Knee Position on Hip and Knee Torques During the Barbell Squat. Journal of Strength and Conditioning Research. 17(4): 629-633. PMID: 1436100
2. Kernozek, T., Gheidi, N., Zellmer, M., Hove, J., Hinbert, B., Torry, M. (2018). Effects of Anterior Knee Displacement During Squatting on Patellofemoral Joint Stress. Journal of Sport Rehabilitation, 27(3): 237-243. doi: 10.1123/jsr.2016-0197
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