Manchester United are allowing Zlatan Ibrahimovic to dictate the terms of his recovery from the recurrence of a long-running knee problem as fears grow over his Old Trafford career.

Sweden's all-time record goalscorer is back in the treatment room after complaining of discomfort in the same right knee he spent seven months rehabbing last year.

Ibrahimovic has missed United's last four games, but manager Jose Mourinho had hoped he would be back in full training at the beginning of February at the latest.

But according to The Sun, the Old Trafford club will not look to rush Ibrahimovic back from his latest fitness setback and are allow him to dictate how quickly he ramps up his recovery.

"The club are letting Ibra dictate the speed of his present recovery," a source at the club told the tabloid.

"He has been unhappy with his form and fitness since returning from the knee surgery last year. He decided to take himself out of the first-team picture and is working on his comeback.

"Ibra is not in any serious pain and he has been a regular in the gym with the conditioning team. They are happy to take the lead from him safe in the knowledge he knows his own body."

United's medical team were said to be "amazed" at the speed of his rehabilitation during the off season and he returned to action pain free in November.

However, the former Barcelona and Juventus striker appears far more cautious with his recovery on this occasion, which could see the date of his return pushed back to ensure he does not suffer another relapse.

He has withdrawn himself from first-team training and is doing extra sessions in the gym at United's Carrington training ground.

After injuring his knee in the Europa League in April, Ibrahimovic missed the rest of the season and was released by United pending his recovery.

In August, United revealed they had agreed a deal worth £125,000-a-week to sign Ibrahimovic for the rest of the season. Three months later he returned for the demolition of Newcastle United.

The substitute appearance is one of seven outings made by Ibrahimovic this season but despite scoring in the Carabao Cup against Bristol City he has failed to recapture his best form, leading to him withdrawing himself from first team duties.

Given the luke-warm resumption to his United career, Ibrahimovic has been linked with moves to clubs in Major League Soccer and the Chinese Super League, whose respective transfer periods are open beyond the end of the Premier League window, which closes on 31 January.

Mourinho has since quashed any suggestion Ibrahimovic could leave United, insisting earlier this week he can be "useful" to the club as they fight on three fronts.

"Zlatan knows that, at the highest level, he is in the last part of his career," said Mourinho, according to Sky Sports.

"But his dream, his desire, his fight was always to end his career at Manchester United, being useful for me, being useful for the team. That I think he can [achieve].

"He just needs to feel really happy with his knee, with his condition, and that I think he can.

"As a leader in the dressing room, as a leader on the pitch – he is a quality player on the pitch, he can do that and I think he deserves that. I am here also to try and help him do that."

Zlatan Ibrahimovic
Ibrahimovic has played seven times this season for United but his return is uncertain. Getty Images