What Causes Muscle Looseness In Knee And Scar Tissue Build Up In Joints?

My daughter had ACL reconstruction seven months ago. She is still having a lot of pain when running. (She is a D1 college soccer player.) The doctor said that she has some scar tissue build up in her joint that he wants to go in and scrap out. Also, he wants to inject her own blood into her tendon to promote healing. The other thing is that he says her knee is much looser than her other knee and wants to tighten it while he is in there. Exactly what does that mean?