Galaxy’s Robbie Keane could miss four to six weeks after knee surgery

Galaxy captain Robbie Keane underwent an arthroscopic procedure on his right knee Thursday and it is uncertain how long he’ll be sidelined.

The Galaxy said he is expected to miss four to six weeks. The procedure was performed by Bert R. Mandelbaum at the Santa Monica Orthopedic and Sports Medicine Group and Kerlan-Jobe Institute at Cedars-Sinai.

The loss of Keane, 35, comes at a bad time for the Galaxy, who have already dealt with injuries to goalkeeper Dan Kennedy as well as starters Steven Gerrard, Giovani dos Santos, Ashley Cole and Jelle Van Damme three games into the Major League Soccer season.

Cole and Van Damme missed a game each but Gerrard (left calf) has not trained for nearly two weeks and will not make the trip to Vancouver for Saturday’s game against the Whitecaps. Kennedy (groin) and Dos Santos (left leg injury), who played the first half of the MLS opener on March 6, both returned to practice recently and their participation in Saturday’s game is unlikely.

Keane, who shares the team lead with two goals, was preparing to play with the Irish national team when he complained of knee pain and was sent back to Southern California to be examined.

Irish Coach Martin O’Neill said Keane was concerned because he had no explanation for the pain, saying only that it occurred March 19 during a win over the San Jose Earthquakes. Keane played the full 90 minutes against San Jose, scoring a goal.

Keane posted a photo Thursday on Instagram showing a heavily bandaged right knee.

The Galaxy and Whitecaps enter the weekend tied for third in the Western Conference with six points.