knee injury worries

Hi all

I'm just after advice from anybody that has had or has experience of meniscus tears. I had one around march this year and had surgery which has resulted in 40% loss of medial meniscus in right knee!

Firstly, i was worried about arthritis but i was told by my doctor to carry on and do all activities as normal. After about 3 weeks post surgery i started squatting to build the muscles in my legs. i began squatting about 35-40kgs and am now at about 60kgs as well as deadlifting around the 60-70kgs mark. I feel my legs are a lot stronger and i have more stability in the joint but every now and again my knee where i had surgery feels slightly tender to touch and sometimes when i walk. Nothing serious like locking or anything just a bit tender, especially after squats.

My question is am i damaging the joint by doing this?
 
All help appreciated!