Saphenous nerve knee pain-How your back pain can cause your knee pain (and how your knee pain can cause your back pain)
In our clinical practice in Portland, OR, we work with disc herniation patients daily. If you came to this link mainly because your back hurts, you might find this site helpful. Commonly, a secondary complaint in these patients is knee pain with squatting or lifting. Often, these patients don’t even mention it because the pain in the back or the sciatica in the leg is much more noticeable. In the course of the exam, we ask them to squat and return to standing. Many of them demonstrate a tendency for the involved knee to drift inward. Some research suggests that this inward drift of the knee with squatting (valgus displacement) is associated with knee pain and knee injury. Put differently, that research shows that a large percentage of people with knee pain demonstrate this valgus tendency with squatting. Other research seemingly contradicts that by noting that many people without knee pain demonstrate this valgus tendency. Which research should you believe? The answer is…both.
The knee is primarily a hinge joint, functioning mostly in one plane forwards and backwards. When it drifts inward under load (squatting weight in the gym) or with many repetitions (running with poor leg strength) then focal areas of mechanical stress occur on the most commonly injured structures in the knee. Under quick, intense loads in this valgus vector can cause acute injury to the ACL, medial meniscus and/or medial collateral ligament. If the valgus movement is not so far or so intense to cause those acute injuries, then a slower chronic knee pain can begin to show. The clinical term for that is patella-femoral syndrome (PFS). How can valgus displacement of the knee be painful in one person and not another? There are several possible reasons, but the most common one is “exposure”. If the valgus displacement does not occur frequently enough to result in frank injury to the above structures then pain is not an issue. This might be a person that feels the pain in the knee and then avoids the bending of the knee with daily activities. We often see that those people tend to round their low back more during lifting and squatting, making them more vulnerable to disc injury too. Sometimes the natural strengthening of the leg with these activities can result in healthy adaptation of the involved structures to become more resilient. For now, let’s talk about when that process doesn’t occur and the knee starts to hurt in the front of the knee and the inside of the knee.
This pattern of knee pain is commonly called patella-femoral syndrome (PFS). The way we describe the process to our patients is to use the analogy of a train on train tracks. The underside of the kneecap (patella) is wedge shaped and the wedge fits into a groove in your leg bone (femur). As the knee is bent, the kneecap slides in that groove somewhat like a train wheel fits onto a train track. When the knee drops inward with activity, the train wheel (kneecap) runs off of the rails (the groove in the femur). If the repetition of that movement is sufficient enough to overwhelm the body’s ability to adapt to those stresses, inflammation may occur to the tissues that help guide the tracking of the knee cap, known as the peripatellar retinaculae. This person might feel pain in the front or inside of the knee after a bit more activity than usual. They might think, “I’m just getting older”, they ignore the pain, maybe take some ibuprofen, and in 3–5 days that pain resolves. The pain then returns with another bout of unusual increased activity…long beach walks, mall walking during Christmas shopping, or a European vacation with way more walking than usual. They repeat the above process and it continues that way for years.
Each of those episodes causes an inflammatory response to heal the bruised retinaculae. Collagen is laid down as part of a normal repair to this mild trauma. Over time, subsequent similar events lay one layer of collagen on top of the other, essentially in a sedimentary process. As the collagen is laid down to repair the bruising, sometimes branches of the nerves to the patella-femoral joint can get trapped in the knitting scar tissue. Once this occurs, bending the knee can tug on those trapped nerves and make them very sensitive. We have found that more often than not, it is these irritated, entrapped nerves that are the structures that are “barking” when knees ache on the front and medial side of the knee. Sounds worrisome, but if this is the cause of your knee pain, it’s a good thing!
These nerves to the patella-femoral joint are branches of the saphenous nerve (SN). The SN is the longest sensory nerve in the human body, coursing from the front of the hip to the inside of the ankle. In some folks it goes all the way to the plantar fascia. The above process may cause the saphenous nerve to be mechanically sensitive. You can find out if that is a part of your knee pain by grabbing a big handful of skin and muscle and pinching about a hand’s width above and below the inside of the knee. If it’s painful, compare it to the other side. More painful on the involved side? If so, try to grasp the skin like that while squatting a few times. Now repeat your previously painful squatting. Better? Then you might benefit from some manual therapy targeting the saphenous nerve.
We often find Dermal Traction Method to be helpful on that saphenous nerve problem. Dr. Phillip Snell developed that technique and you can learn how to do it at this link. If it doesn’t fix the issue, some deeper work in clinic might need to be done. It’s worth noting that the same valgus tendency described above may also irritate other structures on the inside of the knee. To check the integrity of those structures, a proper orthopedic exam of those structures needs to be done. To assess whether the rounded back posture with lifting might be contributing, a proper assessment of the spine should be performed. If you’re in the Portland area, we can help with that, and with the follow up exercises to help improve your movements and strengthen the legs and back. If you’re not in our vicinity, contact us and we can help direct you to one of the doctors that has trained with us in NeuroCentric Approach®. The pain in your knee may not be assign that you have “arthritis” or that you may need a knee replacement. Get it checked out so you can get back in action.