The team announced Wednesday that he will soon undergo surgery.
Downie left the game in the second period as the Avalanche rallied for a 3-1 win over the Kings. He had an assist in the season opener in Minnesota last weekend.
Acquired from Tampa Bay last February, Downie was an immediate contributor, scoring two goals and dishing out 11 assists in 20 games with the Avalanche.
After the season, Colorado signed the 25-year-old to a two-year deal.
Downie was a first-round selection of Philadelphia in the 2005 draft.