What Causes Restricted Movement In Leg Post Knee Replacement Surgery?

after left knee replacement and rehab theraphy all wasfine then later I noticed I had less range of motion ,I had about 110% thendown to 90% maybe less , I cannot bend my lower leg back to sit or help myself get up from a chair, also I cannot work out squats,leg press, leg curls all are limited. I heard about laser leg surgery to stretch ligament without surgery. my orthopedic doctor did put be under and manipulated (?) leg and had my heel of foot hit my buttocs I saw picture did therapy improved range to 90 degrees and slowly went back were I lack rangw of motion I doont need full range just enough so I canwork out and function better I can pay my medical costs do not have to rely on my HAP SENIOR PLUS if need be