Hi, I Recently Received Acl And A Meniscus Surgery Jan

hi, I recently received acl and a meniscus surgery Jan 6. 1017. I have noticed when I try to walk on it (which my doctor has requested) I notice that as I walk on it (very lightly and slowly), it feels as if a muscle in between my knee is tight and wont loosen up regardless of the amount of physical therapy I am doing. What should I be doing or should I be concerned?