I currently visited walmart where i slip and fell on clear liquid. Walmart stated to me that i once done with Physical Therapy they would settle my claim. I have Post Traumatic Arthetis of my knee. How much should i send a demand letter in for. *NOTE WALMART WILL TRY TO LOW BALL ME SO I THINK I SHOULD START HIGH. Post tramatic Arthetis there is a 25% chance that i will need Knee replacment. I am under 27 in good health until this happened.