The 26-year-old has been training with the Lions Super 14 team since the beginning of the year when his brother - Springbok flanker Jacques Cronje - moved from the Blue Bulls.
Cronje is expected to turn out for the Golden Lions side in the lesser Vodacom Cup in the next fortnight, and will then move up to Super 14 rugby in mid-April.
He became infamous following the 2003 World Cup selection race row where he was alleged to have refused to share a room with black team-mate Quinton Davids.
The row engulfed South Africa and both players were left out of the World Cup squad.
Cronje signed for Harlequins in England, but sustained the knee injury and had his contract eventually annulled without ever playing a game for the club.