Britton was placed on the disabled list on April 16. Steve Melewski of MASNSports.com noted Orioles manager Buck Showalter was unsure how long it would take Britton to return.
The 29-year-old left-hander made two rehab appearances in Double-A on April 28 and 30, allowing two hits and one earned run in 1.2 innings.
Britton was the anchor of the Baltimore bullpen that led the American League with a 3.40 ERA in 2016. He led the AL with 47 saves and had a 0.54 ERA en route to finishing fourth in Cy Young voting.
Prior to going on the DL this season, Britton had a 1.29 ERA with 10 hits allowed, six strikeouts, five saves and three walks in seven innings.