Joe Smith of The Athletic reported Hedman initially suffered the knee injury on March 30 but played through the ailment during the Bolts' playoff run to their second straight Stanley Cup title.
The 30-year-old has emerged as one of the NHL's best defensemen in recent years, taking home the Norris Trophy in the 2017-18 season after registering 17 goals, 46 assists and a plus-minus of 32 while averaging 25 minutes, 51 seconds in ice time. He also won the Conn Smythe Trophy as the postseason MVP after helping the Lightning win the 2020 title.
A three-time All-Star, Hedman remains one of the key figures for a Lightning team that'll seek a three-peat next season. The team is stacked, led by Hedman, superstar winger Nikita Kucherov, goalie Andrei Vasilevskiy and centers Brayden Point and Steven Stamkos.
Barring any setbacks, he should be recovered before the 2021-22 season gets underway.