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How to Screen for Knee Stability

Welcome back to Squat University. The past few weeks, we have discussed how having good mobility at the hip and ankle allows us to reach full depth squats. Today I want to talk to you about the knee and its role in the squat.

The knee is basically a hinge that is stuck between the ankle and hip joints. In order to reach full depth, we require the knee to fully hinge open and close. This motion is described as flexion and extension. It can be measured by drawing a line on the outside of the thigh and the lower leg. The smaller or more closed the angle is, the more flexion the knee has.

Most athletes do not have an issue in achieving full knee flexion. The main problem we see is the inability to control the knee during dynamic movements like the squat. When I say unstable, what I mean is that often athletes have a difficult time keeping their knee in a steady and unwavering position. Athletes who develop pain in their knees or sustain traumatic injuries (such as the torn ACL) tend to have unstable knees. When we view the squat from the front we see the knee tends to wobble around like crazy and at times rotate inward, collapsing towards the mid-line of the body.

The ideal position of our knees is to be in direct alignment with the feet. An effective cue is “drive the knees wide”. With this cue, an athlete can establish the knee-over-toes alignment during the squat. The knee is considered to be unstable anytime its position deviates from this ideal alignment. The inward cave in of the knee (labeled a valgus collapse) is the most common fault we see. If the foot is placed in the stable tri-pod position during the entire lift, there is no way for the knee to collapse in or out.

The knee joint would therefore benefit from increased stability to limit this inward collapse. Improving the control of our knees allows us to avoid injury meanwhile, increase the efficiency of our movement. By increasing efficiency of our movements, we can produce more power and increase strength. Who wouldn’t want more power, more strength and avoid injuries?!

Let’s talk about screening the knee. Before we enter this discussion, there is one point I would like to make. If an athlete presents with stiff ankles and/or hips, this issue will likely result in an unstable knee. For this reason, always address the hip and ankle prior to screening the knee. If you skip the hip and ankle, any knee stability we try to establish will be short lived.

After clearing the ankle and hips, we can now focus on the stability of the knee. We need to view our squat in both double and single leg stance. The double leg squat can sometimes mask any stability issues. Therefore, I would like to look at pistol squats on one leg. Often times, an athlete may be proficient in a double leg squat but then demonstrate valgus collapse with the pistol squat.

To start our assessment, stand with your feet at a comfortable width with your toes in a relatively straightforward position. Perform a deep squat. Next assume a single leg stance and perform a deep pistol squat. What do you notice? Does your knee wobble around and fall inward or can you keep it in line with your feet?

It can be helpful to also test the loaded squat. The weighted barbell allows us to test the competency of our movement. The more weight on the bar, the higher the demand on the body. Very often I see athletes who can perform the perfect bodyweight squat but when they perform a weighted back squat, their form turns to crap. It is never okay or justifiable to lose good technique to achieve a new 1 rep-max personal record.

The weight on the bar means nothing if our technique goes to crap! If the knees collapse during a maximum squat attempt, the risk of injury greatly increases. Period.

In the past year there has been a number of world records set in the sport of Weightlifting. Tremendous weight moved in the blink of an eye. All of them were performed with good technique. These weightlifters spend day after day perfecting their movement with the barbell. No matter if you’re performing a world record snatch or a simple bodyweight squat, good technique is a necessity. If you want to stay healthy and reach your true strength potential, focusing on stabilizing the knees is vital.

I hope this lecture is helpful in highlighting how a stable knee is relevant to the perfect squat. Thank you for reading.

Until next time,

Dr. Aaron Horschig PT, DPT, CSCS, USAW

With

Dr. Kevin Sonthana PT, DPT, CSCS
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