In 1946, he won the silver medal at the DM in the Senior Division, when he lost the final bout to Svend Møller.
On 24 February 1954, in a match against the Swede Olle Bengtsson in Gothenburg for the Scandinavian middleweight Championship, Christensen was knocked out in the seventh round.
In 1954 and 1955 he toured in the United States, where he fought eight matches, winning only three, including defeating former World title challenger Billy Graham, but losing the other five.
Before he could get to his feet and while the referee was still counting, McCormack struck Christensen down again, causing a general uproar, both inside and outside the ring.
Christensen lost the European middleweight championship in his next bout against the Hungarian 3-time Olympic gold medalist László Papp, who won on a technical knockout in the seventh round in Vienna on 16 May 1962.
During July 1964, at the Forum in Copenhagen, Christensen had a rematch against László Papp for the European Light-Middleweight Championship, but he was knocked out in the fourth round.
In his last match as a professional at the age of 38, Christensen tried once again to regain a European Championship, this time as a Light-Middleweight, but he lost to Italy's Bruno Visintin.