"I know it bothered him this spring and it's popped up a few times to where we've had to shut him down," Melvin said.
Sogard has been on the disabled list since the beginning of the season, but because of a neck strain that's since alleviated. The knee discomfort, present at times last year, worsened in his most recent rehab game with Class A Advanced Stockton on Wednesday.
Sogard, 29, played in 120 games for the A's last season, mostly at second base, and hit .247/.294/.304.
Alvarez close to rehab assignment Right-hander Henderson Alvarez (shoulder surgery) is on tap for a bullpen session on Sunday before beginning a Minor League rehab assignment, Melvin said on Saturday.
Alvarez remains on track to join the A's rotation in late May.