Cycling UK Forum

Sounds like it's everything except your bike. The ACL reconstruction seems to be quite a while ago so it's less likely to be that. As others have mentioned, it's more likely to be the sciatica you talked about.

Sciatica usually sends a tingling feeling down one side of your leg which is what this sounds like if it feels like it's you hamstring.

The best thing to do would be to check your saddle position/design to make sure it's not agitating your sciatic nerve. I you want to troubleshoot it bit then wearing some sort of knee brace or compression knee sleeve may help to rule out any knee problems if the pain is still present.