Suppose you have two bad knees. You could be looking at a double whammy: first one knee operated on, then the other. If you are in such a situation, you may be consoling yourself by thinking, “Well, at least after the first operation, I’ll know what to expect, and the second will be easier.”
Not necessarily. In fact, the opposite may be the case.
Pain sensitivity in patients who undergo staged bilateral total knee arthroscopy (TKA) is greater after the second than the first operation, a study by South Korean researchers has found.The study consisted of 30 patients with osteoarthritis in both knees who underwent total knee arthroscopies at a one-week interval (if this means, as it seems to, that only one week separated the surgeries, that’s important to keep in mind when interpreting the results). Self-reported pain was greater after the second operation than the first. When the knee was at rest, pain levels averaged 49.3 (using a visual analog scale) vs. 21.8. The difference was narrower, but still statistically significant, at “maximum knee flexion”: 83.7 vs. 74.3.
The amount of post-operation pain-relief medication that had to be administered supported the findings. After the second operation, patients received almost three times as much opiates.
What’s going on?
The speculation: “Surgical injury induces hyperalgesia [which simply means increased sensitivity to pain] via central sensitization.” The more detailed technical explanation: The hyperalgesia is probably caused by “neuroplasticity, or central sensitization, triggered by persistent nociceptive inputs from the first operated knee that alter sensory processing and sensitize subcortical structures.”
So: If surgery really does often beget further surgery -- as I believe -- these findings are unfortunate. They’re one more thing to ponder for patients thinking of going under the knife.