Christopher EllisCEO Dynamic Physio Therapy

Why Your Quad Won't Fire After Knee Replacement

16 Oct 2026 · 1 min

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In this segment Christopher Ellis explains why the quadriceps (quad) may fail to contract effectively after a total knee replacement. He identifies two primary physiological reasons: a temporary nerve block from anesthesia and direct trauma to the quad muscle from the surgical incision. Because the quad is the main knee extensor, surgeons often place patients in an immobilizer and limit weight‑bearing for the first week or two to prevent falls. Ellis cautions against prolonged immobilizer use, noting that extended wear can cause joint stiffness. He then introduces neuromuscular electrical stimulation (NMES) as a physical‑therapy technique that can accelerate quad re‑activation and help patients regain strength sooner.

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And then the last one, this is one that makes people freak out a lot, is the quad. Your thigh muscle might not work for a small period of time. You know, that may be due to the nerve block. They also, they have probably done an incision on the quad muscle. So for, you know, maybe a week or 2 sometimes, the quad doesn't quite fire as well as it should. And in fact, they know this in the hospital. They might put you in an immobilizer in weight-bearing, and that's just because the quad does extension of the leg. They don't want you to fall over, so they might do that initially depending on how you're doing just to get you in weight-bearing. But don't think that you should be in an immobilizer the whole time. Don't be sleeping in it. That's going to stiffen you right up. So just know that there are workarounds for that. There's something called NMES, which is a type of muscle stimulation that we usually utilize in physical therapy to help kick that quad back on sooner.