Boyd W. Haynes III, MD
Although knee replacement surgery has become commonplace, it has a reputation for being challenging for both the surgeon and the patient. As a surgeon, I must be both a construction expert, an engineer, mathematician, and an expert surgeon all rolled into one, as I remove my patient’s diseased knee and replace it with an artificial implant, making sure it fits perfectly, bends appropriately and that the patient’s leg has the correct stability when I’m finished. My patient then must recover from this major surgery, which requires time, effort, and patience to deal with the discomfort and the healing process. One of the more interesting aspects of knee replacement surgery is the effect it has on the nerves in and around the operative site of the knee. In this article, I will discuss why nerve pain after knee replacement surgery is common, why it happens, and how it typically evolves and resolves over time.
Knee replacement surgery technique has advanced through the years, becoming increasingly “tissue-sparing,” meaning that we no longer cut through major muscles and tendons as we did in the past, reducing the pain during recovery and the healing time required after surgery. It also helps the patient to retain a much more “natural-feeling” knee. However, surgical technique hasn’t evolved to the point where we can avoid cutting all the nerves in the skin and tissue around the knee when we make our surgical incision. Therein lies the rub.
The knee has several large nerves and branches that work to control the lower part of the leg, the ankle, foot, and toes and provide feedback to the brain from these body parts. There are the saphenous, peroneal, tibial, femoral, and obturator nerves, some which have several branches and twigs. Some of these nerves lie in the back of the knee, some to the side and others in the front. The skin around the knee is full of nerve endings as well.
While surgeons will take care not to cut or damage large nerves whenever possible, sometimes the peroneal nerve or a branch gets cut during the incision process. A study by the Mayo Clinic found that the saphenous nerve is sometimes inadvertently caught and closed in the incision sutures. Unfortunately, it can form a painful neuroma in 20% of TKA patients, although researchers are not clear why that happens. Fortunately, most TKA patients only need to manage the “typical” and expected nerve pain after surgery.
So, when I say typical and expected, what does that mean? After surgery, when the anesthesia and the nerve block wear off, patients usually report numbness of the skin around the incision (but not numb enough, right?). As your bandage comes off and you shower, you may notice that your skin feels odd as you shower. All of this is perfectly normal.
On the other hand, some parts of your skin may become hypersensitive to touch. You may feel extra pain in specific areas of your knee as you become more mobile and do your exercises at home and then outpatient Physical Therapy. Feelings of tingling, electric zings, burning, and pins and needles are all normal and indicate that your nerves are awakening and healing from the surgery.
As progress is made in Physical Therapy, some patients report feeling a wide “band” around their knee, even though there is nothing there. This also is a common nerve-related phenomenon which tends to resolve or ease as time passes. As you kneel for the first time, you may notice that your knee feels strange, numb, or painful. This too tends to resolve with the passing of time.
Knowing what to expect with your knee replacement is important to a great recovery. If my patients experience nerve pain that is atypical, I will work with them to resolve the problem. Letting me know if you have nerve-related issues, such as restless leg syndrome, or Neuropathy before surgery is also a good idea, so that we can be prepared if issues arise.
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