"I know he has this problem. He loves judo. He lifted a guy, threw him, and twisted his spine," Lukashenko said in an interview.
Lukashenko had been hoping to play ice hockey with Putin but the Kremlin leader postponed the match, he said.
"He tells me: 'We are not prepared yet to take on your team.' He has damaged his spine somewhere. In a judo match. He was on the mat and hurt his spine," Lukashenko said.
Putin's spokesman Dmitry Peskov declined to comment. The former Soviet republic of Belarus has close but sometimes rocky relations with its former colonial master.
Putin, a judo black belt who began a six-year presidential term in May and turned 60 in October, was seen limping at an Asia-Pacific summit in the Russian port of Vladivostok in early September.
Three government sources told Reuters in late October that Putin was suffering from back trouble. Several foreign trips that had been expected around that time but were never officially announced by the Kremlin have not taken place, including a trip to India.
Putin has held regular meetings with officials but has not traveled throughout November. The Kremlin acknowledged that he had suffered a sports-related injury but gave no details.
The Russian leader is expected to resume foreign travel in December.