Left knee joint. With unknow disease.

Hello sir,im 28years old male from bhutan concerned with my left knee problem. At first my knee started to swell around joint without any injuries (only that i played football 2,3 times a week). I got too concerned with the swelling n  went for checkup. At first docs came up with the possible causes like gout,sephtics or else n instructed me for lultrasound,xray n etc including blood n urine tests. All seemed normal until they injected 5 times on my knee.(first inject was the morphine n the rest no idea..but they took out some liquids n said they need to run some tests). Still unknown cause n defination for my disease i went home but when i woke up nest morning my knee became severe..it started giving too much pain n swelling at same. I couldnt walk becoz of the swelling n it hurt more(maybe becoz of the injections). I was bed sick with unknow disease.