Some patients do poorly after knee replacement and some do great. Now there may be a way to figure out who is going to do poorly, and it relates to nerve hypersensitivity. This fits with our idea that many patients with knee pain and arthritis really have nerve issues elsewhere like the low back. Let me explain, and then I’ll review a new study on hypersensitivity before knee replacement being a risk factor for more pain after the surgery.
How the Low Back Can Cause Knee Pain
I’ve highlighted many studies that have connected knee pain to issues in the low back. So while the link between the two isn’t new, the new hypersensitivity finding is interesting, and it just adds to the growing list of reasons the low back should always be fully examined before treating, and certainly before doing surgery on, the knees.
One study found that patients who were 65 and older who had low-back pain prior to knee surgery experienced worse outcomes and reported less satisfaction after their surgery. The higher the degree of back pain in these patients, the higher their degree of dissatisfaction with the results of their knee surgery.
This study fell on the heels of a prior large study that found that 54% of patients who underwent a knee replacement had low-back pain. The study discovered that those who had low-back pain also had significantly poorer surgery outcomes, including more knee pain and less knee function than those who didn’t have back pain prior to surgery.
Even a low-level irritation in the low back can impact alignment when you walk or run, eventually leading to knee pain (see my brief video below demonstrating my own back and knee issue).
Hypersensitivity Before Knee Replacement May Mean Chronic Knee Pain After
The new study researched links between hypersensitivity prior to total knee replacements and chronic pain following the surgery. At 12 months after surgery, the subjects were assessed for pain levels. Those who didn’t have a 30% or more reduction of their pain (19% of the subjects in total) at 12 months were put into the chronic pain group. Researchers found that the chronic pain group had increased hypersensitivity prior to surgery when compared to the group they considered the nonchronic-pain group. Researchers concluded that hypersensitivity prior to knee replacement is a risk factor for chronic pain following surgery.
Signs Your Low Back May Be Causing Your Knee Pain
If you have knee pain, there are some signs that it could be due to an issue in your back. First, clearly if you have both knee pain and low-back pain, this is a huge red flag that you need to find out if your back is the culprit. If it is, knee surgery isn’t going to fix the problem and will only make matters worse as you deal with having a surgery you may not really need. Keep in mind, however, that you can have a nerve problem, such as a pinched nerve, in your back and have little to no pain at all in the back. The nerves in the low back supply the lower limbs, and pain can present itself (termed referred pain) anywhere along the nerve branch.
Second, if you are experiencing chronic or constant bouts of tightness in the hamstrings along with your knee pain, this is another good indicator that it could be due to a problem in the low back. Finally, believe it or not, bunions can form when the foot muscles weaken due to poor supply from a stressed or injured nerve in the low back. If you have accompanying knee pain as well, this is another big red flag that the back needs to be fully considered.
The upshot? At the end of the day, spending only 5 minutes with a patient and performing a cursory exam that focuses only on one body part like the knee is a recipe for disaster. This is especially true when the game plan is to amputate that joint. If you have low back pain and knee pain, be very careful about getting a knee replacement until your doctor spends a significant amount of time ruling out that your knee pain is due to irritated nerves!