painful knee and calf for more than 2months

well i am perplex to what happening to me, i am experiencing an abnormal knee and calf injury. i'm trying to describe the problem and feeling the best way i can, i demand to pls try understand the complexity of the problem.
the origin of the problem i cant tell exactly, had lots of movement and hardwork in my like, i had a big and tight cramp (calf) one in a football match, had to b substituted for that, but after a few mins, it was ok, there were pain after but it got ok.
another event is when i was carrying a bucket of wet rocksand, on a rocky path, i felt my knee slip but it regain its place, n i found nothing serious in zat coz i was able to carry out the activity tho i took precautions after but the knee has weaken a little n there was a little pain.

the pain i am feeling know is quite bizarre, i can walk without pain, but there is some stiffness and weakness in my knee wen i sit on my knee and stand. acute bending on the knee cause me pain in the knee and the inside of my calf.

the pain occurs mainly when i bend my knee and also sitting on the knee.cant sit on it like before, too much pain.
i had use voltarene gel on it for some time but no amelioration.