I slipped and fell at walmart?

I slipped and fell in the produce department of wal-mart. I strained to try to keep from falling and came down in a kneeling position on my right knee. When I got up I walked with a limp and I reported it to wal-mart. The first employee who responded noticed the produce sprayer that sprayed water on the veggies was facing out in the walkway. I also noticed the floor was wet and there were rugs in front of the produce that were wet and no wet floor signs were in place. They took pics of where I fell there was a mark about a foot and half long on the floor where I slid and fell. They also said they took pics of the sprayer. I had a dirt mark mud type substance on my knee but they said they were not allowed to take pics of my knee. I filled out an incident report and went to ER a few hours later. Nothing broke put me off work 2 days, told me to follow up with my Dr, and offered pain meds which I told them I didn't want because I don't tolerate them well. Did not offer anything else for pain I called back next day to ask for something for pain said to take Motrin OTC four tabs 800mg. I followed up with my ortho dr on the second day I seen the PA in the walk in clinic best they could do. He viewed x-rays from ER said looked ok diagnosis right knee contusion and strain. Said to wear brace from 3-6 weeks till healed and if gets worse or starts to swell alot to come back. I am concerned because I have had problems with this knee in the past osteoarthritis, but have not been to Dr. in over 2 years. I am not sure if more problems will arise from this I still walk with limp and its sore and painful but only 2 days out from accident so who know what will come. Do I have a case and what am I entitled to? I read Wal-Mart cases are tough but I am sure they were negligent because sprayer was facing walk way and no wet floor signs were posted and I am sure rugs were in place because of the potential of water getting in the floor from the sprayers.