Sit on the floor, one leg straight. Press the back of the knee down into the floor, squeezing the quadriceps for 5 seconds. The simplest possible knee-rehab move — works from post-op day 1 with zero risk.
Form cues
1Press the knee straight down — feel the quad on the front of the thigh tighten
25-second hold, 10 reps
3Heel may lift slightly — that's fine
Common mistakes
⚠Lifting the whole leg (that's SLR, not a quad set)