Sri Lanka's cricket board confirmed Karunaratne sustained the injury while batting in the nets on Tuesday to prepare for a limited-overs tournament.
It did not comment on whether he would join the three-Test series in the West Indies, but sources said the 30-year-old opener was unlikely to be ready.
The board said Karunaratne would be examined by a specialist "to determine the injury management and return to play timeframe".
The left-hand opener has played in 49 Tests and scored 3,186 runs.
Sri Lanka have adopted advanced software used by football club Barcelona to manage their injury-prone cricketers.
The players wear devices during training and tournaments to monitor fitness and performance.
Under new coach Chandika Hathurusingha, Sri Lanka have been rebuilding after a year of humiliating defeats.
The national side bounced back in a tour of Bangladesh in January, thrashing the hosts in all three formats of the
First Published: May 2, 2018, 7:00 PM IST