Knee pain going down stairs (but not up): what it means

Pain that's clearly worse going down stairs than up is one of the most recognisable signs of patellofemoral pain — runner's knee. Descending asks the quad to lower your whole bodyweight while lengthening, with the knee bent — that combination puts the highest compressive load on the joint between the kneecap and thigh bone. Going up is hard work, but it loads that joint less.

The step-down is so characteristic that it's used as the signature test for this condition: slow, controlled step-downs off a low step, counting clean repetitions before pain passes mild. It's both the diagnosis clue and the progress marker — as the joint rebuilds capacity, your clean-rep count climbs.

Nothing about stairs pain means damage. The joint is irritated and under-built for the load, not injured — scans are typically normal and aren't recommended.

Short term, trim the aggravators: take stairs down more slowly (or lead with the sore-side-second), cut deep squats and very long sitting for a couple of weeks. That calms it — but the fix is strengthening the quads and hips over six to twelve weeks so the joint can handle descent again. Full phased approach in the runner's knee guide below.