It is agreed and well understood by surgeons and therapists that following surgery to repair or reconstruct a torn or ruptured anterior cruciate ligament (ACL), it is vitally important to restore normal knee range-of-motion. It may be helpful for you to understand a bit more about why this is so important.
Studies show that small losses of either knee flexion or extension can lead to knee osteoarthritis. This is especially true when there is any damage to the cartilage. And restoring and maintaining knee motion is one thing patients can do to possibly prevent (or at least delay) osteoarthritis from developing.
With proper measuring, the therapist can identify even small (three to five degree) losses of motion early on. This is important while the graft tissue is still remodeling in order to regain full motion. Waiting too long can result in a stiff, painful, and weak knee.
Long-term studies following patients who have had ACL surgery show a significant increase in the number of patients with loss of knee motion who develop abnormal joint findings as seen on X-rays. Such changes were observed as early as five years after ACL surgery in patients who had loss of knee motion. On the flip side, patients with known cartilage damage but who maintained normal knee motion were much less likely to develop knee osteoarthritis.
If you and your therapist are having some personality conflicts you may want to ask to be assigned to a different therapist. But it sounds like your therapist is working in consultation with the surgeon following priciples of best practice in this area.
Letting your therapist know you are doing your best and asking some questions about his or her thinking in your case might be a helpful place to start. We can at least assure you that a progressive rehab program aimed at quickly restoring normal knee motion following ACL surgery is extremely important.