As far as CAN he do it? - I honestly do not know. I've had a knee injury and they are tough to deal with even mostly healed and doing stuff - hyperextended my knee and still had to perform as a mascot. But, seeing him dance through the injury, I think he could do it. If they are planning on him doing the jive though... no, he'd have to withdraw I think.
Personally, I'm tired of Mark and want him to go home. I like Chelsea, and feel bad for her being partnered with a jerk like him. Game or not, you show respect for someone perservering through an injury and attempting to dance. Ralph didn't just up and say "I can't dance" or do a prima donna thing in the process, hence why the show of respect.
Heck, IMHO even as annoying as Derek can be, I think he'd show a lot more maturity and respect his fellow dancers and attempting to do their best.
Hopefully that will be the case, but I think they're going to keep Mark in there as long as possible, and the bottom two will be Romeo and Ralph with either going home based on skills.