HOUSTON - 76ers point guard Jrue Holiday missed his fourth straight game Wednesday night with a sprained left foot. One of the curious elements concerning the injury is that no one seems to know when it happened.

Holiday has not played since he scored 26 points on 28 shots in the Sixers' 96-89 loss to Chicago on Dec. 12.

Like his point guard, Sixers coach Doug Collins said he did not know specifically when Holiday was hurt.

"Damien Wilkins was kidding him that it might have happened from landing after taking [all] those . . . shots," Collins said. "But we don't know when it happened."

Collins reiterated that he did not have major concerns about the injury, which has kept Holiday out of the lineup for a full week.

With Holiday out of the game against the Houston Rockets, former Villanova and Roman Catholic star Maalik Wayns made the first start of his career.

Collins was asked if he had any concerns that Holiday's injury had worsened.

"I don't have any," he said. "Once he's good to go I don't think this is an injury that would be chronic unless you try to [play] too soon."

Bynum's exam

Center Andrew Bynum will be examined Thursday by his personal orthopedist, David Altchek, in New York. Bynum, who has not played or practiced this season because of chronically injured knees, said this week that he hoped to be cleared to step up his workouts.

The Sixers no longer have a time frame for Bynum's return.

Bynum has bone bruises and weakened cartilage in both knees. He said this week that his right knee felt fine. The left knee, the one he said he hurt while bowling last month, was still hurting, Bynum said.

Contact John N. Mitchell at jmitchell@philly.com. Follow on Twitter @JmitchInquirer.