You strained your quadriceps, your patellar tendon, or the whole extensor chain that straightens your knee, and the advice you got was some version of "rest a few weeks, ice it, do some physio, see how it feels." That advice isn't wrong.

A vastus medialis strain has a way of becoming a recurring character in your training life rather than a one-time event. You rest it, the pain fades, you rebuild your quad strength the way every physio handout tells you to, and then a few months later — a lunge, a sprint start, a deep squat — it flares again.