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Knee Injuries in Youth Athletes: Why they happen & how to prevent them

Updated: Nov 4, 2021



Introduction I always get asked by patients “how can I prevent knee injuries?”. My response is always the same no matter who it is, you can’t. I’m sure when you started reading this blog post that’s not what you thought you were going to hear. But hear me out. There is no way to completely prevent knee injuries from happening. That is like trying to say you can predict which direction a striker is going to cut to, which direction the keeper will dive to, or even which way the wind is going to go. There are some elements that we just cannot control. Now, that is not to say there is nothing that can be done to help decrease the risk of injury. In this post, I will try (without being too wordy/use of medical jargon) to give a basic description of what the knee is, and why it is so susceptible to injury. I will also provide a quick guideline of things to focus on when performing knee prevention programs.


What does the knee joint do? To understand how to prevent injury, you have to understand what the knee joint actually is and what it does. To sum it up briefly, the knee is the fulcrum of the lower extremity, lying between foot/ankle and the hip. It is the connection of the femur (the major weight bearing bone of the hip) and the tibia, (the major weight bearing bone of the shin). Along with the patella, the femur and tibia help distribute the body weight of a person to the floor.


What some people ignore, is it also distributes a ground reaction force back up to through the body. When walking the ground reaction force can be up to 2x of your body weight. This can quadruple with the additional force of running. This means the knee takes force down towards the floor, as well as on the way back up. This is a lot of stress on a joint which is made up of 3 bones and no big muscles around it for stability. Between the upwards and downwards forces and the knee being in the middle of it all, it makes it arguably one of the most vulnerable sections of the lower extremity.


Now there is “perfect bone alignment” which distributes weight perfectly and would never allow injury to happen. But, who’s perfect anyway? There are definitely certain things which increase the vulnerability of this joint. Now, I could go on and on about all of the really cool anatomical and physics reasons, but, this is one blog post and I’m pretty sure I would bore most of you. One thing that I think is the most important to talk about is Quadriceps angle or Q angle for short. This is an angle from the center of your tibia (shin) to the Anterior Superior Iliac Spine (hip bone). The greater this angle, the greater of a chance you have you have to getting a knee injury. This is also one of the reasons why ACL and other knee injuries are more common in women. As women tend to have figures which give them wider hips which will widen the Q angle.


If I had to sum up why knee injuries occur in 2 words, I would use muscle imbalance. I purposely stayed away from using the phrase “muscle weakness” here. Most athletes are not “weak” in general. These athletes have strength, and are much stronger and powerful than the average Joe that walks into my clinic. The problem is that athletes use movements which play advantages to their strength. The body then can compensate almost any athletic move required of it using this “strong” portion, and allowing these athletes to compensate for other muscles which are weaker. Eventually, this stronger muscle will try to support the knee in a way that it cannot function, and BAM muscle or ligament failure and a knee injuries occurs.


Why knee injuries occur Now every person is different, so by no means are these the only reasons for knee injuries. If I were to write a comprehensive list, I would run out of my character limit! However I have listed a few reasons which are more common, and ones I find most often in patients who walk through my door.

1. Quadriceps to Hamstring ratio.

• This is really important! Most, but not all, athletes tend to have really strong quadriceps muscles but neglect hamstring. These 2 muscles work opposite to each other at the knee. The quadriceps work to extend or straighten the knee, and the hamstrings work to flex or bend. Having equal “push to pull” is key for knee stability and inability to do so puts the ACL in its greatest deficiency and potential to tear.

2. Gluteus Medius weakness

• This muscle is on the side of the hip next to the powerful gluteus maximus, and is one of the greatest neglected muscles in training. This muscle is really important for posture in single limb stance and any side-side lateral movement. It is really important in overall knee positioning for squatting, stairs, and bending in general.

• If/When this muscle is weak, when in a squatting position the knee will cave in/ go medially/valgus. This positioning is the most common way to increase knee injury. The number one way you can get this muscle starting to become engaged in squatting, leg press, or other exercises is to place a band around your knees, and push out against the band during a squat. This prevents this “caving in” or valgus positioning and cues this muscle to engage.

3. Squat/Jumping form

• It is very important that when practicing and training that proper form is always used. As any coach you have ever had can tell you, practice makes perfect. Well, I like to refer to it more as practice makes habit. If it’s a habit, then you will do it without even thinking about it in a game. When squatting, feet should be about hip width apart and knees should always be tracking towards between the second and third toes. The most common mistake I see is having knees go in/valgus either on the way down or on the way out of a squat. By practicing jumping from the floor, a box, on one leg, two legs and varying for different scenarios all while using proper form is vital in preventing knee injuries during sport.

4. Flexibility • As important as it is to make sure the knee has proper strength, it is equally as important to have good range of motion of the hip and ankles in order for optimal squat and jumping form. If the athlete is lacking in hip flexion or ankle dorsiflexion (typically due to tight gastrocnemeus/soleus complex) than compensation will occur at other joints in order to make the motion happen.


Preventing knee injuries Unfortunately, even if athletes have: strength, strong glutes and perfect hamstring:quadriceps ratio injuries can still happen. As I mentioned, all knee injuries are not 100% preventable or predictable. But these are some ways to help them from occurring. This by no means is everything you need to do, but some helpful tips to add to strength training days.

• Hip flexor stretch

• gastroc/soleus stretch

• IT band stretch

• clamshells/reverse

• Sidesteps

• Dips

• ER wall isometrics

• Wall Sits

• Jumping Progression

◦ Double: double

◦ Double : single

◦ Box jumps up

◦ Box jumps down

◦ Same with single legs

• Jumping side:side


In one sentence Athletes should strive to counteract any muscle imbalances they may incur from regular play while working to improve form & flexibility to have the greatest chance of avoiding knee injuries.


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