Taking my granddaughters to school yesterday and we ran downhill, not terribly steep and quite slowly. My left knee gave way. It's doing it quite alot on downhill bits. I wonder if anyone else is having this. Over the last few weeks, my knees have started twinging. Going downstairs can hurt. I'm wondering whether knee supports might help, or are there any exercises for tender knees. I am wondering whether to try doing more running on grass.