The swelling is the reason you don't feel that your flexion is improving. In addition to the swelling you can see and feel, there is likely internal swelling. Your body needs time to heal from the trauma of surgery.I still have swelling and ROM isn't really progressing satisfactorily.
You are still only a month into a year-long recovery. I found this chart really helpful in understanding why it takes so long:
In these early day, the most important muscle to exercise is your patience muscle so you don't set yourself back.
Good luck.
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