Newcastle United beat Manchester United 2-0 in the Premier League on Monday thanks to early headed goals from Alexander Isak and Joelinton at Old Trafford, an ugly culmination of one of the most miserable months in the home side's recent memory.

With five losses in their last six league games, Manchester United languish 14th in the standings on 19 points, their worst placing to end a calendar year since they were 15th in 1989. Newcastle are fifth on 32 points.

"One of the more difficult moments in the history of Manchester United," said manager Ruben Amorim, who called the team's position in the table embarrassing. "It's a very difficult moment, but we have to fight to win the next game."

Isak got the visitors on the scoresheet in the fourth minute when he leapt to head home a pinpoint cross from Lewis Hall with both Harry Maguire and Lisandro Martínez failing to pick him up.

It was the 11th goal in 11 games for Isak, who has scored more Premier League goals in December than any other player with eight.

Newcastle doubled their lead in the 19th minute in near carbon copy fashion with Anthony Gordon sending in a cross that Joelinton headed in.

The win marked Newcastle's second victory at Old Trafford in 40 league visits, dating back to 1972.

"We know the hurt this fixture has had for us historically, it wasn't lost on us," Newcastle boss Eddie Howe said. "We didn't necessarily use that with the players, but it was a big step forward for us today. I think we need to win games like this to achieve what we want on a regular basis."

It is also the first time since 1979 that Manchester United have lost three consecutive league games at home. Their 18 goals conceded in all competitions in December is their most in a single month since March 1964 (also 18).

The score could have been more lopsided, with Isak lashing a shot past keeper André Onana in what would have made it 3-0 in the first half before the offside flag went up to the relief of United fans.

Soon after, Sandro Tonali missed an absolute sitter when he ran onto a flick from Gordon but clattered it off the woodwork.

"It feels great. We haven't won in a long time here, it was a great performance and the perfect way to end the year," Isak said. "The challenge was to have the same intensity here as we do at home -- the first half paid off."

While the home side struggled to get out of their end in the first half, Rasmus Hojlund and Casemiro both squandered chances just before half-time.

Hojlund was played in by Martinez but sent his shot across the face of goal, inches from the far corner, while Casemiro unleashed a shot that sailed wide, burying his head in his hands.

Ruben Amorim's men were better after the break and Maguire's diving header that goalkeeper Martin Dúbravka grabbed at least had the Old Trafford crowd -- who had booed their squad off the pitch at the break -- cheering their effort.

One of the game's ugliest moments was when the Old Trafford crowd lustily booed struggling Joshua Zirkzee when Amorim took him out of the game in the 33rd minute. There were huge swaths of empty seats, however, by the time the final whistle blew.