The Aviva Premiership club have confirmed that Thomas suffered a ruptured Achilles during last weekend's league game against Exeter at Sandy Park, and he faces a lay-off of six to nine months.
"We are bitterly disappointed to lose Lee, who was really starting to find his feet in a Wasps shirt," Wasps rugby director David Young said.
"I thought he was excellent against Leicester and played very well against Exeter until he was forced off, and it's a big blow to lose him for so long.
"We really feel for him as I know he was thoroughly enjoying his first few months here, but we will have to focus on getting him back fit and ready for next season."
- Sports & Recreation