Colombian missed eight months after injury in JanuaryStriker has managed just one goal in five appearances

Radamel Falcao is having to ice his left knee following every training session and match to mitigate further damage following the serious injury he suffered in January.

With Falcao already facing a fight to regain a first-team place, the condition of his knee is bound to be a factor when the club weigh up whether to make his loan permanent next summer.

Falcao was signed by Louis van Gaal on the closing day of the transfer window in a season-long deal worth £16m to Monaco. The 28-year-old had suffered anterior cruciate damage in January, an injury that prevented him from playing in Colombia’s World Cup campaign.

Falcao takes instructions during one of his five appearances for United. Photograph: Kieran Galvin/EPA

It was the third severe knee injury of Falcao’s career and ruled him out for eight months. He was unable to return to action until 10 August when he scored in Monaco’s 2-1 defeat to Lorient. It is understood that since his arrival at United, Falcao’s need to apply an ice pack on his left knee following any kind of physical exertion has surprised United players over the degree of treatment required.

On signing from Monaco, Falcao admitted the injury still concerned him. Having made a first international appearance since the problem, Colombia’s 1-0 defeat to Brazil in Miami, he said: “Because of the injury I felt so nervous. Almost like it was my first time with the national team. And I expect it will be the same before I play my first game for Manchester United. I’m so happy to be back, and I am also happy about being able to join United. Physically I feel spectacular. I have been able to play without any kind of trouble.”

While the striker earns at least £190,000 a week, which is paid by the club, there is also an option for the 20-times champions to make him a United player in the close season.

As well as the state of his knee, Falcao’s form will also be closely observed. So far he has managed only one goal in five appearances and is currently laid low with a calf problem.

While Van Gaal is unsure when Falcao might return the manager made it clear last week that a two-forward approach he previously utilised upset the “balance” of the team. Even before the calf injury, Robin van Persie was preferred for the 2-2 draw at West Bromwich Albion on 20 October, with Falcao coming on as a second-half substitute.

The club recently published a picture of Falcao with an ice pack on his left knee in the changing room, in which he is sitting alongside Ander Herrera, Juan Mata, Ángel di María, Antonio Valencia and Marcos Rojo.