Stiffness — and its extreme form, arthrofibrosis (scarring of the knee) — is the #1 reason people end up regretting a knee replacement. In this episode I explain what stiffness actually is, who’s most at risk, how it’s treated (including manipulation under anesthesia), how much motion you really need, and the research — from losartan to newer compounds — that could one day prevent it. I’m an orthopedic surgeon who replaces knees — and a knee replacement patient myself who went into my own surgery worried about this exact problem.