You're going to have to do a little homework to come up with a number....but here are a few ideas on things to check.
1. Find out what Dr. James Andrews (Birmingham, Alabama) charges for the surgery, and treatment. Since you are a BB, lawyer can argue that you must have the very best treatment as an athlete, and Andrews is the recognized expert for treating athletes. Also find out what HealthSouth's hospital fees are for this.
2. Find out the transportation costs associated to get there and back, allowing for a travel companion to assist you (which will definately be necessary)
3. Figure out the income you're going to lose both during the recovery phase, and after (ie healthy but leg not in BB shape to earn money)
4. Figure out what the physical pain should be worth to you.
5. Figure out what the emotional damage to you is going to be (frustrations of rehab, lost quality of life, trauma of watching muscle you have worked so hard to build disappearing, ect.)
6. Price out what rehab is going to cost....and for a hell of a lot longer than three months!!! Think at least 6 as a minimum...and you may want to provide for additional massage sessions and TENS treatments afterwards.
7. If not being able to drive is going to cost you cabfares during your recovery, price that out.
Basically, don't be thinking in the tens of thousands....be thinking in the hundreds of thousands or even a million or so. Believe me....the company doesn't want this case to see a courtroom. Just look at how much money courts tend to hand out to accident victims when a big corporation is involved. Remember what that woman got for a little burned skin that SHE spilled on HERSELF from McDonald's? If she got that, then think about how much you should get for a torn ACL (worst injury a person can get just about) when the store is clearly negligent in their failure to keep the aisle free of slippery substances! Consult with a good lawyer...the good ones will always work for a percentage of settlement/award without any cost to you if they fail to win you money. Contact your state's bar association, ask around, ect. to find the best possible lawyer who specializes in this type of suit. You should make out like a bandit. Best of luck.