non-surgical acl. feeling stuck at 5 months after tear.

hi, i tore my acl and miniscus in last dec and started rehab in jan itself. my doc said no surgery. earlier i had no pain whatsoever and i was continuing with the rehab. for some reason i couldn’t do it for 2 weeks and pain is back in my knee. its not there when i walk but when i’m going downstairs it is. could it be patellar tendonitis? pls reaxh out if you’ve experienced the same. thanks