Word 2003 and 2007 are the most common versions on the market
Microsoft has lost an appeal against a court judgement that told it to pay $240m (£160m) in damages.
In August 2009, a US court awarded the damages to i4i which claimed Microsoft had infringed its patents.
The patents cover the use of XML, a mark-up language that preserves data formats across different programs.
The judgement also required Microsoft to remove the i4i technology from its Office software suite and stop selling the infringing programs.
The injunction on sales began in January 2010 and applied to any Microsoft Office software, specifically Word 2003 and 2007, containing the infringing patents.
Since it lost the first round of the legal battle, Microsoft has been stripping the disputed technology from its Office products.
Soon after losing the initial case, Microsoft filed an appeal asking the court to re-think its decision. In December 2009, a panel of judges upheld the initial ruling.
In this second appeal, the court again re-affirmed the original ruling and spelled out why that decision was made. In court documents spelling out their reasoning, the three appeal court judges said there was evidence that Microsoft knew i4i technology was patented before it turned up in Office programs.
The appeal is not the last that Microsoft can make. The court documents are now being sent to the other appeal court judges who will decide if Microsoft has grounds for a wider review of the case.
The decision on the whether to hold that review is due within the next six weeks. If that is refused then Microsoft can appeal again to the Supreme Court.
I4i's patents date from 1998 and outline a way of "manipulating the architecture and the content of a document separately from each other" that invokes XML as the means of doing this.
I4i founder Michel Vulpe said he was "pleased with the court's continued decision to uphold the injunction".