Center Andrew Bynum confirmed a report Sunday night that he injured his left knee while bowling last Saturday. Bynum – who has yet to play for the Sixers because of a bone bruise and cartilage problems in his right knee – said he now has the same issue in his left knee. "Obviously, I think it happened bowling, to be honest," Bynum said on Sunday before the Sixers-Cavaliers game at the Wells Fargo Center. "I don't think anybody could have told me I couldn't do that. I was doing squatting and low-impact training. So, it is what it is. The cartilage is in a weakened state. That's what the doctors tell me. Now, I'm going through the same thing that I have on the right, in the left. It's identical." On Friday, Bynum told the media that he suffered "a setback" in his left knee but did not disclose how it happened. Bynum, who said he bowls regularly, was asked what he did, specifically, to hurt himself. "I didn't do anything," Bynum said. "I didn't twist it or fall. I just kind of broke off cartilage and it made the bone bruise bigger." The Sixers' center said he didn't notice his left knee had swelled until after he was done that day. So how, exactly, does something like that happen?