The Dynamo overcame a 1-0 defect and avenged their loss to the Galaxy in the 2011 MLS Cup.
The Galaxy took the lead within the first 10 minutes when Chad Barrett found Buddle streaking into the box, and the striker calmly slotted a first-time finish past Tally Hall.
Houston struck back though, and dominated most of the play until a Mike Magee own goal evened the match in the 38th minute. Brian Ching struck a shot off the crossbar, and Magee mis-controlled the rebound, which ricocheted into the net.
The home side deservedly took the lead early in the second half. Hainault was quickest to the near post on a Houston corner, and nodded home to give the Dynamo a lead it wouldn't lose.
For Los Angeles, the loss dropped it to 0-5-2 in its last seven matches, and the defending champions remain stuck at the bottom of the Western Conference standings.
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