Can an Achilles Tendon Injury cause Knee Pain?

Many active individuals struggle with either a nagging injury or even a traumatic injury to their Achilles Tendon. And because this may be considered a “common” injury and sometimes mislabeled as a “minor” injury, many people are lulled into a sense of security regarding the recovery time. This can lead to the false assumption that rest and ice will fix this injury, or that an ankle brace should do that trick. But the truth of the matter is, the longer an Achilles tendon injury lingers, the greater the risk of having to deal with sudden knee pain. 

(Oh, and rest and ice (aka the RICE approach) is an outdated approach to injury management - so don’t be tempted to do this. It leads to longer recovery times and chronic pain - but I digress.)  

Back to my original topic - This resulting knee pain is due to the concept of the kinetic chain and how ground reaction forces transfer up the chain - from joint to joint. And while I won’t dive too deep into the topic of biomechanics (because, many people would instinctively yawn), the take home message is:

Faulty joint mechanics/movement patterns due to an injury at the ankle directly leads to faulty joint mechanics/movement patterns and pain at the knee.

Background and Anatomy of the Achilles Tendon

But why? Well first let’s look at the Achilles tendon. A tendon is the structure that connects a muscle to a bone, and the Achilles tendon is the largest and thickest tendon in the body. It is composed of 3 different muscles and attaches at the base of the heel. 2 of these muscles cross the knee joint and play a role in bending the knee. 

This is the most basic connection of how an injury to this tendon would affect the knee - but there’s so so many more reasons. 

The real reason for sudden unexplained knee pain following an Achilles tendon injury is compensation strategies. For example, if your ankle/heel hurts, you may instinctively protect your heel/Achilles and change the way you walk. While this may be beneficial in the short term, this sudden change of your natural walking pattern can cause havoc up the chain. 

More specifically? Ok, here goes nothing

If you have sustained an injury to the heel, many times people try to protect this area by suddenly landing with more force on the forefoot (the “ball of the foot”) when walking as opposed to the proper heel strike when walking (think Beatles - Abbey Road picture for a great demonstration of heel strike). 

This new walking pattern of always striking on your forefoot, not only exacerbates Achilles pain over time, but leads to muscle tightness to the calf muscles → remember, these calf muscles cross at the knee, so the movement patterns of the knee are now directly affected. 

Additionally, and more importantly, the ankle joint itself (which, for the purpose of this blog, we will call the “front” or “top” of the ankle.) can become very stiff and no longer move properly. This is a huge problem and leads to compensation at the knee and even opposite hip to make up for the lost ankle range of motion - notably during squatting activities.

How does the compensation pattern at the ankle affect the knee?

This question is the nuts and bolts of “why” the knee can become irritated following an Achilles or ankle injury. 

In the above example of decreased heel strike during walking → which leads to subsequent increased forefoot strike → ultimately leads to increased pressure on the patellar tendon of the knee and the kneecap itself.

When we properly attain heel strike while walking, the quadriceps muscle (the big muscle on the front of your thigh) momentarily relaxes while your knee is locked in an extended position. But when you strike with your forefoot, the knee also remains barely bent, thus not allowing the quad muscle to relax. This increased effort of the quad muscle group leads to patellar tendonitis and/or pain underneath the kneecap.

Additionally, the above example highlighting limited ankle joint mobility which limits ankle dorsiflexion (toes to nose motion) causes a separate compensation pattern. This pattern is best visualized when performing a body-weighted squat. If the ankle joint is suddenly tight and unable to provide enough dorsiflexion range of motion, then you will be unable to perform a deep squat. The common compensation pattern for this is the toe-out position of the affected ankle or excessive weight shift toward the opposite leg - both of which can cause unwanted extra stress/pressure on the knee.

OK, enough with the jargon, what does this mean for the patient with Achilles pain? Or the patient who has already developed knee pain following and injury to their Achilles?

Simply this: to the person out there who is reading this and is upset about... or wondering WHY their knee suddenly hurts after an Achilles injury, know that there is a reason for why this is occurring.

This is an important concept because the stress and anxiety of an injury can stem from the unknown cause. And when you surround yourself with the right clinicians - who are willing to spend the time it takes to listen to the you and take a deep dive into your injury - then this connection is both thoroughly explained to you and demonstrated to you in your session. Now, suddenly the injury and/or pain isn’t quite so stressful and scary. 

Not only that, when you have a clinician who understands the “why” and then takes the holistic approach to look at how the entire kinetic chain interacts throughout your movements, then the correct treatment approach can be developed.

Moreover, we can and will alleviate the stress associated with going down the internet rabbit hole of searching "Why does my knee hurt?" - suddenly thinking you have a more serious knee injury or torn meniscus.

So, Now What?

This is exactly what we offer at Flow Physical Therapy and Wellness in The Woodlands, TX, where we specialize in Osteopractic Physical Therapy services to deliver a unique and holistic approach to Orthopedic injury rehab.

This is the reason we allot 60 minutes of one on one Physical Therapy sessions - so we can look beyond the Achilles, or assess beyond the knee, to determine if there is more than meets the eye in your specific and always unique case. 

If you feel you have sudden and unexplained knee pain, or even hip pain, or you are struggling with a nagging Achilles tendon injury and want to prevent the eventual progression of the injury - click the button below to learn how to get started. 

Dr. Patrick Thompson, PT, DPT, OCS, Dip. Osteopractic

Owner of Flow Physical Therapy and Wellness

832.299.5447