Answer by taking a quote from the following article:

Larsson was born in Helsingborg, Scania. His father, Francisco Rocha, is from Cape Verde, and his mother, Eva Larsson, is Swedish. His parents, who never married and split up when he was 12, decided that he should take his mother's surname because they felt it would make it easier for their son to be accepted in Sweden. He credits his father for his love of football.

At the end of the 2003-04 season, Larsson left Celtic on a free transfer and signed a one-year contract with Barcelona with an option for a second year. Larsson's contribution in Barca's La Liga win in his first season there was disrupted by serious injury. He scored 3 goals in 12 Liga games and one goal (against his former club Celtic) in four Champions League matches. After the match against Celtic, he said: "It was very difficult for me to celebrate my goal because I had so many great times here." On 20 November 2004, during the 3-0 victory in El Clasico against Real Madrid, Larsson tore the anterior cruciate ligament (ACL) and meniscus in his left knee. Despite his injury-hit 2004-05 season, playing only 16 games, Barcelona took the option to extend his contract.  In December 2005, Larsson announced that at the end of his contract, which ended in July, he would leave Barcelona and return to Sweden to end his career. He revealed that he had refused an offer by club president Joan Laporta to extend his contract to the end of the next season. On the announcement of his departure, Ronaldinho said:  In Larsson's final match for Barcelona, his substitute introduction was pivotal to win the 2006 Champions League final. Larsson assisted both of Barcelona's goals in a 2-1 win over Arsenal. Thierry Henry paid tribute to Larsson's contribution to Barcelona's win after the match, saying, "People always talk about Ronaldinho, Samuel Eto'o, Ludovic Giuly and everything, but I didn't see them today, I saw Henrik Larsson. He came on, he changed the game, that is what killed the game. Sometimes you talk about Ronaldinho and Eto'o and people like that; you need to talk about the proper footballer who made the difference, and that was Henrik Larsson tonight." Indeed, his ability to give Barcelona the cutting edge required to overcome Arsenal was noted by the international press. In 2005-06, Larsson scored ten goals as Barcelona won La Liga for a second consecutive year.

What was the injury?
Larsson tore the anterior cruciate ligament (ACL) and meniscus in his left knee.