Okay the past week or so my left knee has been hurting on and off. I ride fixed clipless, with a brake. I never skid. I have a 16th and a 18t cog that's a suicide hub. I stopped riding around September for school. At the end of december I started riding again but only on the 18 cog so I wasn't backpedaling. Few days ago I finally tried the 16 cog and my knee has been hurting from backpedaling. But here is where it gets tricky. I did a ride with the 16 with very light back pedaling and my knee didn't hurt. But today I went out on the 18 cog and halfway through the ride my knee started hurting, so I'm confused now.

I thought the cleat might have moved but it hasn't. Are my knees just weaker now and do I just need to build up the strength little by little?