CSNNE.com just broke the following news:

Paul Pierce will miss the Celtics' upcoming four-game road trip, and may be sidelined for as many as two weeks, because of a knee problem that required a medical procedure on Wednesday.

Team owner Wyc Grousbeck said Pierce began feeling discomfort in the knee after Tuesday night's victory over Indiana. He described the problem as an infection that required drainage, but said he wouldn't describe the procedure as surgery.

The Celtics.com twitter adds:

Paul Pierce underwent arthroscopic irrigation on right knee to clean an infection at NEBH today; he's expected to miss next 2 weeks.

Clearly this is terrible news for the team, especially in the wake of Kevin Garnett's thigh bruise, no matter how minor that injury might be. This obviously makes the upcoming four-game road swing much more difficult, but it will test the mettle of this group. Let's see how they respond to this adversity.

So who can explain in layman's terms what arthroscopic irrigation means?