Zimmer Holdings Inc. and Seikagaku Corp. have won a patent-infringement trial brought by Cambridge-based Genzyme Corp. over a treatment for arthritis in the knee.

A federal jury in Boston said Friday that the Gel-One product, made by Tokyo-based Seikagaku and distributed by Zimmer, does not infringe on a patent held by Genzyme, a unit of Sanofi. The patent was ruled invalid because it covers obvious variations of earlier work.

Genzyme’s Synvisc-One product was the only single-injection treatment approved by US regulators until Gel-One was given clearance in March 2011, according to the complaint.