My understanding is there are two types of range of motion. Passive - which is assisted (an MUA, or PT moving or you forcing with a strap) and Active - which is totally on your own with no help. What my PT has told me is that your passive range of motion is your personal max. If you can maintain your passive range of motion farther out from the surgery - it should convert to an active range of motion if you stick with the program.

After my initial knee replacement, I developed arthofibrosis, which is an official diagnosis painful restriction of joint motion, with scar tissue forming within the joint and surrounding soft tissue spaces and persisting DESPITE aggressive rehabilitation. My initial PT was considered medically aggressive since for 4 months and 3 hours per day. They started me at this level because I had a documented history of excessive scar tissue from two other surgeries. However, despite PT both my passive and range of motion would decrease weekly. My PT identified that I had arthofibrosis at about 2 months post op - but after a knee replacement, they won't do a lysis until you are at least 6 months post replacement.

What my surgeon explained to me is that anytime you damage your body with trauma or surgery - your body heals with scar tissue. When a joint is involved, you are in a race between the scar tissue and your motion. The lysis surgery allows the race to restart when the surgeon removes the excessive scar tissue - but you have to race to prevent the NEW scar tissue from preventing any gains in your motion. Hence the aggressive PT again - but at a higher level.

My PT tells me the passive number at each session. As long as I'm hitting what the surgeon had me at coming out of the lysis surgery - I'm winning the race.

Hope that explains it