Houston has a dislocated right elbow, an injury he suffered in last weekend's loss to the San Diego Chargers.
The 24-year-old Houston was scheduled to undergo an MRI on Monday, but it was postponed because of swelling in the elbow.
The Chiefs (9-2) also could be without two-time Pro Bowl linebacker Tamba Hali for their rematch with the AFC West rival Broncos (9-2), who have the league's top-ranked offense.
Hali suffered a slight ankle sprain against San Diego, according to Chiefs coach Andy Reid, but may not be able to play against Denver.
Houston appeared in the locker room Monday with his arm tightly bound and in a sling. When he was approached by reporters, Houston said he was told not to say anything.
Zombo was signed as a free agent in the offseason from the Green Bay Packers. Moses joined the Chiefs at the start of the regular season as a waiver claim from Green Bay.
Houston and Hali both went to the Pro Bowl last season and have 20 sacks between them this season. But the pass-rushing duo failed to record a sack of Peyton Manning two weeks ago, when the Broncos defeated the Chiefs in Denver to hand Kansas City its first loss.
ESPN.com Chiefs reporter Adam Teicher contributed to this report.