Why is my left knee feeling discomfort after eating the glucosamine plus chondrotin supplement?

I tried Kordel's Glucosamine Plus Chondrotin 500/400 because I want to cure my right knee. But after few days, my left knee started to feel discomfort and I stopped taking it immediately. Why is it hurting my left knee?

Hi , I have been taking various supplements since my knees started to hurt(age 38), in mixed supplements all included glucosamine or chondrotitinesulfat. I have not noticed any issues taking the suppliments, however my knees hurts due to chondromalacia. Last doctor I have seen told me to take 1000/1000 glucosamine and chondroitinsulfat . Have been taking this in liquid form for a month and no issues.  My knees hurts both and pain alternates. However I think pain alternates due to different positioning while I am sleeping, applying pressures on damaged cartilage differently. I am going to continue take supplement long term. 

Forgot to mention that I sit in front of computer playing PC games almost every night for average 4 hours in my bedroom with air con and short pants. Is this one of the reason causing my knee discomfort in a long term?