Knee Pain or Under-Loading the Knees when Squatting

It’s fairly common for an athlete to avoid (or work around) knee flexion during squat activities. This is often seen in the Front Squat and Back Squat, but can be prominent when receiving a snatch or a clean. If an athlete is experiencing knee pain with squatting, there may be many contributing factors to this. Additionally, support and retraining by a coach and physical therapist can help guide the athlete back to confident, pain free lifts. 

Let’s dive into WHY knee pain with squatting + avoidance of knee loading may occur, how this manifests in common lifts, and what we can do to address it!

How do we know if an athlete is avoiding knee flexion or loading their knees? An athlete may show a greater posterior shift, or a tendency to reach behind them while squatting, to minimize knee flexion. This helps keep the shin angle from moving forward, which may be the problematic aspect of the descent for them. Furthermore, the athlete might lock their knees early during the concentric phase (ascent) of the squat, relying more on a hinge pattern to rise using their hamstrings and glutes, rather than allowing the knees and hips to move upward together.

Reasons this may occur: 

•  Former knee injury + Quad loading insufficiency: has the athlete had a history of a knee injury, such as an ACL tear or a meniscus injury? Depending on their rehab course, they could have insufficient use of their eccentric quad control during knee flexion. In this case, the avoidance of knee flexion may be partially psychological (lack of trust for the knee to absorb force at this angle) or a default pattern of shifting away from greater knee angles when the load capacity is diminished.

•  Pain in the front of the knee at specific angles: whether they’ve had a former injury or not, they may have anterior knee pain at specific angles of squatting. This sometimes arises early (approx 30deg of knee flexion, aka initiating the descent), at halfway/ 90deg of the squat, and sometimes, all the way into the deep squat. Usually, the pain arises through the first half of the motion (30-90deg) and may actually diminish as they complete the squat! This is because the greatest muscle activation of the vastus medialis and the tibialis anterior muscle occurs when we approach knee flexion1. Additionally, retro patellar compressive forces are the highest at this angle, and continue to decrease as the knee flexion angle increases2. Therefore, they may experience more discomfort through these ranges, but this does NOT make this movement a bad thing! In fact, loading at these angles is necessary, especially for general life function. The athlete may be experiencing a load intolerance here, which can be trained and adapted!

•  Mobility restrictions in the hips, spine, or ankles can limit anterior shin angle movement: this could potentially contribute to knee pain. These restrictions may have existed before training or could stem from an injury or pain elsewhere, contributing to movement pattern faults that prevent proper knee flexion. One common issue I observe is that limited anterior ankle mobility restricts shin angulation during knee flexion, and prevents the load adaptation at the front of the knee from occurring — and across time, this under-loading contributes to pain! 

•  Trained under-use of knee flexion when squatting: has the athlete been trained to avoid this movement altogether? Some outdated schools of thought include “don’t let your knees go over your toes when you squat!”… While this has been proven to be safe and essential in both strength training and rehabilitation, backed by substantial evidence, it remains a common misconception among many athletes and coaches.

What can happen as a result of under-loading the knees when squatting?

THE FRONT SQUAT: In the front rack position for the front squat, the barbell is positioned more anteriorly, encouraging a more upright torso. As a result, the body needs to sit down instead of back to keep the weight centered over the mass. This does require greater knee and hip flexion. If knee flexion is restricted during the descent, leading to a "sit-back" pattern, we may see some of the following: 1) The torso and shoulders may struggle to remain upright, potentially causing upper back or anterior shoulder pain, and making the lift more difficult. 2) The pelvic angle may tilt forward, hindering hip flexion and limiting squat depth and tolerance. 3) During the ascent, the torso might lean forward more, causing the knees to extend early. This shifts the lift into a hinge pattern, making it harder to complete successfully.

THE BACK SQUAT: In the back squat, adjusting the bar placement can optimize weight distribution for the athlete's mechanics. When the bar is positioned lower on the back, the trunk angle tilts forward to accommodate the center of mass. In a high bar position, the torso remains more upright but should still have a slight forward inclination, which is a natural movement pattern. In a low-bar back squat, the athlete may demonstrate less hip and knee flexion due to the increased trunk angle. This can serve as a SOLUTION to pain, an effective pain-management strategy in the short term, which I often recommend to my patients. It allows for adjustments that align with the athlete’s needs, enabling continued participation. Sometimes, this adjustment is temporary, helping the athlete manage knee pain before gradually returning to a higher bar placement. However, in both positions, knee pain can arise if the load is insufficient or if the athlete isn't adapted to the specific angles during the lift.

THE CLEAN/SNATCH: The knee pain, or avoidance of loading the knees, can manifest in the Olympic Lifts. Does the athlete keep the knees relatively locked out when they pull from the floor, avoiding maintaining quad tension through the lift? (See my blog post: Block Snatches/Cleans in Rehab for more info on this). Does the athlete avoid getting low to receive the bar? Does the athlete keep the knees relatively straight, while the torso angles forward, in the catch of a power clean/snatch? Does the athlete exhibit discomfort when trying to receive the bar in the squat, demonstrated with a more forward trunk angle, or avoiding getting low? These are all ways we can see it happening. 

Before I continue, let me be CRYSTAL CLEAR… correcting this movement pattern isn’t as simple as telling the athlete to “keep your chest up more!”

Why?! Because in this situation, the angle of the torso directly reflects what’s happening at the hips and knees. Yes, you may be seeing their torso dump, and yes, shifting focus away from the knees can help with pain from a psychological perspective. However, forcing an upright position may place more undue stress on the mid-back, and they may feel frustrated and more uncomfortable with this. Additionally, this doesn’t address the underlying mechanical issues in the squat in the first place! 

How we can address knee pain and under-loading knees during squatting:

1.  First, train the breathing and bracing in the set up. Whether the bar is on the front rack, the back rack, or even during pulling from the floor in the olympic lifts, help them find a confident and strong foundation. This position is what we want to maintain throughout the lift, something they can have maximal control over. And to reiterate what i said above, turning the attention away from the knees for a bit can have a great psychological impact. No, i am not telling the athlete to “keep their chest up more when they squat!”, but rather establishing a set up BEFORE the lift. 
2.  Work through controlled ranges of the squat. Cue the athlete to adopt a “sit-DOWN”, not “sit-BACK” pattern, and give them permission to allow the knees to come forward. Even if this is above parallel at first… they are still progressing their load tolerance, psychologically improving their comfort with loading their knees, and improving neuromuscular control of the initiation of the descent. 
3.  Incorporate quad loading progressions. This can be with wall sits, spanish squats, step downs, split squats, etc. In fact, in early stages (and in more sensitive knees), ISOMETRICS are the way to go here. 
4. Add the relevant mobility work. If the athlete truly is limited in spine, hip, or ankle mobility, those will be added in prior to the loading strategies. 

The name of the game is this: HELP THE ATHLETE FEEL CONFIDENT WITH LOADING THEIR KNEES AGAIN! :)

 Ready to learn more? Have specific pain problems that are limiting your performance goals? Czarbell is here to help. Reach out at [email protected], or schedule an appointment with me through the main page of this website, to learn more!

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1. Han D, Nam S, Song J, Lee W, Kang T. The effect of knee flexion angles and ground conditions on the muscle activation of the lower extremity in the squat position. J Phys Ther Sci. 2017 Oct;29(10):1852-1855. doi: 10.1589/jpts.29.1852. Epub 2017 Oct 21. PMID: 29184305; PMCID: PMC5684026.

2. Larsen, S., Kristiansen, E., Nygaard Falch, H., Estifanos Haugen, M., Fimland, M. S., & van den Tillaar, R. (2022). Effects of barbell load on kinematics, kinetics, and myoelectric activity in back squats. Sports Biomechanics, 1–15. 

3. Hartmann, Hagen, Klaus Wirth, and Markus Klusemann. "Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load." Sports medicine 43 (2013): 993-1008.