Jonas Werner, who has served as the Swedish national team's doctor since 2021, spoke ahead of the World Cup squad announcement after head coach Graham Potter made what he described as a "very, very difficult decision" to leave Kulusevski out of the 26-man party for the United States.
"It has been a long story," Werner told Sportbladet.
"Dejan has done everything to get ready to play World Cup football again. Now he was not ready. This is because he has not played football for over a year. And the medical assessments pointed in one direction. It is a combination of different things."
Werner went on to explain the particular difficulty of cartilage injuries in the kneecap region.
"They are difficult to treat. Cartilage has no blood supply and no nerves. They do not heal in the usual way. In addition, his injury is in a place where a lot of strain occurs for a football player. The kneecap slides back and forth over the femur. An enormous compressive force is developed. It is likely that his injury has not healed enough for him to cope with that strain yet."
Kulusevski sustained the injury in a Tottenham match against Crystal Palace in May 2025 — an incident initially minimised by then-Spurs manager Ange Postecoglou. The 26-year-old subsequently underwent surgery and a second clean-up procedure as he suffered repeated setbacks attempting to return to training at Hotspur Way. He spent an extended period of rehabilitation abroad, and was not yet back in full training at the club at the time of the squad announcement.
His personal determination to be fit for the World Cup was not in doubt. He had set the tournament as his target and spoken publicly about his desire to be involved. Roberto De Zerbi, who took charge of Tottenham in April and guided the club to Premier League survival, was more measured: "For me, it's difficult to understand how he can play at the World Cup if he didn't play any games this season."
Werner was supportive of an eventual return.
"He won't give up hope. He's getting plenty of help from the club and others who are helping him with his rehabilitation. I have good hopes that he will play football again."
The next target is a return for the start of next season. Whether that is realistic will depend on how the knee responds over the coming weeks. A player capable of transforming Tottenham's attack will have been absent for over 14 months by the time pre-season begins.