Arenas said his knee was sore Tuesday morning and did not play in that night's game against Atlanta.
After the game Arenas told reporters he had faked the injury so guard Nick Young could get more playing time. Young scored 24 points against the Hawks. The team fined Arenas on Wednesday.
After Wednesday's practice, Arenas first said he wasn't talking, then appeared before reporters offering a halfhearted apology for his actions.
"I screwed up again, so I just want to say sorry," he said. "I wasn't really thinking that this was going to be another media outburst. It's like everything I do now, someone, tit for tat, tries to blow it out of proportion."
Arenas didn't start Thursday against Milwaukee, but suffered a groin injury just three minutes after coming into the game in the first quarter.
The Associated Press contributed to this report.