pete, the knee will still be sore after 4 months although walking is soon after the operation. Mine is 19 years old now with no problems except i only have 90 degree bend due to all the injuries i already had. Absoloutely work the physio as much as you can to get at least 115 degrees. I found that excercise one day and not the next was best as daily workouts just made it very sore. 12 months and it will be as good as it is going to be. Always feels like a slightly rusty hinge in operation. I went back to work after 5 Months and able to lift and carry , build scaffolds and work quite well apart from i can never kneel due to the angle i have. I am still walking quite well on it and pain free. Hoping it will stay that way. Its design life was 15 years. Its had a few bumps but the bone cement holds well. Good result for me as i was unable to walk aged 51 without a lot of pain.