My dad is 62, and has previously torn his ACL on his left knee. He did that in February 2005 and had reconstruction [allografted] in April 2005. The doctors were amazed by how quickly he recovered. He has been running and skiing all winter.
I'm not sure if the ACL thing is even relevant to this problem, but I thought it would be best to give enough information.
Anyways, he was walking in between two closely spaced pallets at the store he works at, when he turned his left foot to fit through and something happened in his left knee. He continued working through the pain, and by the time he got home, it was swollen to a pretty large size. This was Thursday night. (the 16th) It is still swollen now. The swelling is VERY clearly concentrated on the left side of the knee. He can bend and straighten it completely, and squatting causes no pain. Walking, however, is painful, and after about one hour, makes it very, very, swollen.
What could be the problem? How can it be treated?