Allen, who has not played since April 10 due to persistent swelling in his right ankle, watched practice from the sideline Monday and will not play Tuesday against the Miami Heat. An MRI scan showed loose bodies floating in the ankle, which has bothered Allen since late March.
Those bodies do not have to be large to cause Allen discomfort.
"The other day when it swelled, they said it could be the size of a grain of sand," Allen said. "But they're not supposed to be in there, so as [the ankle swells], they move around, and as the swelling goes down, they rest."
Allen could have an X-ray Tuesday or Wednesday after he tests the ankle again. He ran Monday on a machine that takes a percentage of his body weight off the ankle, and he sported running shoes while he watched practice. The fact that he can move the ankle at all means he does not have loose bone chips, which could get lodged and render his ankle immobile, Allen said.
Allen was pessimistic about playing in the regular season finale Thursday against the Milwaukee Bucks and had no plan beyond that game. The Celtics are still planning on having him available at some point in the playoffs, with head coach Doc Rivers saying Allen is still included in the team's postseason plans.
"It's just not healing or it's not getting better," Rivers said. "I should say it's getting better, slowly. Until it gets all the way, we're just going to keep sitting him."
Paul Pierce, Kevin Garnett, Rajon Rondo and Mickael Pietrus all sat out Friday's loss to the Hawks, but Allen was the only player Rivers seemed concerned about not returning to the floor soon. Pierce expressed a desire to play Tuesday, although he is likely to rest at least one of Boston's final two games, and Rondo may rest his ailing back another day.