Sitting on haunches.....always a bad exerciseregistrar should have known!!!
Was your post surgical pain and swelling mild before commencing that exercise and then aggravated after it? Just think, the prosthesis takes months to get really well healed into the bone.
There are two ways you can most safely exercise to improve flexion if the knee is settled enough. One is to place your foot onto a footstool or chair and hold under the front of your knee with your hands. then lean forewards keeping your hips low to gently stretch into flexion. In this way you can control the load your knee is under and you should feel a firm stretch but dont go into pain. Hold for a long slow stretch and dont walk too soon after you finish. Sit on a stool and do some pendulum swings to get everything moving again.
Also using the bike Start with 5 mins on a comfortable setting to warm up and then lower the seat so that it is a little uncomfortable to go around. Work for another 5 minutes.
Although 110 deg is OK for everyday life you need more to get up and down stairs and get in and out of car easily.
Does your knee get warm or hot after exercises?
Is there pain behind your knee with the flexion stretches?