"It was really hard to move, it just felt stiff," said Howard, who spoke to the media about his DL trip after Sunday's game. "I mean, there's been times where it kind of felt stiff before, but the pain and the stiffness was just too much to where I knew I couldn't go out there and do it. I had to go let them know."
Howard is scheduled for an MRI on Monday. He said he would know more about a course of action once doctors are able to take a look at his knee.
"I guess we'll see what happens tomorrow to get a better understanding of what is going on inside of there, and then address it from there," Howard said. "As far as surgery or any other injections, right now I guess it's too early to tell."
The first baseman initially got an MRI on the knee in mid-May, but after he received a cortisone shot, he continued to play. Howard hit .337 in his first 30 games after the treatment, but had just four hits in his last 31 at-bats before going on the DL.
Howard was held out of the lineup four times on the club's 10-game road trip, but played Friday against the Braves and hit a towering home run -- his 11th of the season. Howard, who is in the second season of a five-year, $125 million contract, is hitting .266 with 43 RBIs in 80 games.
Manager Charlie Manuel also noted that Howard's foot was bothering him. Howard said he has had some "small discomfort" in the bottom of his left foot, but his knee is definitely the main area of concern.
Howard was able to crack a few smiles Sunday, and when he was asked if there's an activity that bothers him the most with the injury, he replied "Yes, doing interviews."
Darin Ruf was recalled from Triple-A Lehigh Valley to replace Howard and is 2-for-4 with a double and two runs in two contests. Meanwhile, Domonic Brown will take over the cleanup role in Howard's absence. The All-Star left fielder hit an RBI triple and a solo homer in a 7-3 win Sunday over Atlanta.
Todd Zolecki is a reporter for MLB.com. Stephen Pianovich is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.