Yes, he had a bracer on his knee since like 10 years, he injured it early afaik. But it obviously got worse, he didn't have this problem catching his own weight after punching when missing Klitschko in the rematch.
Someone close to Helenius suppose next fight might be belt owner from America. Brian Minto NABA-title, Fres Oquendo NABA Interim, James Toney WBO NABO...anyone else?