The court upheld its ruling, first made in August, which found Microsoft had infringed a patent from Canadian company i4i in its 2003 and 2007 versions of Office and Word.
It was found that the way Word uses XML to open certain types of files infringed on a 1998 patent from i4i to do with XML handling algorithms.
The ban will stop the sale of available versions of Word and Office from 11 January until the feature is removed, and see Microsoft coughing up damages of around £182 million. It will not affect sales of software that have already happened.
The good news Microsoft says it has been preparing for this ruling since August and is hopeful it will have versions available by the time the injunction date lands, with this "little-used feature" removed.
It said in a statement: "We expect to have copies of Microsoft Word 2007 and Office 2007, with this feature removed, available for US sale and distribution by the injunction date."
It added: "Beta versions of Microsoft Word 2010 and Microsoft Office 2010, which are available now for downloading, do not contain the technology covered by the injunction".
Microsoft has also said it may file a further appeal, so we may not have heard to last of this yet.
Ultimately if you were hoping to get your hands on a copy of Word or Office in the New Year, best get it quickly or get to downloading the 2010 beta instead.