Flintoff last played for his county in a Championship game 11 months ago
Andrew Flintoff took two wickets and suffered no immediate ill-effects after his surprise comeback for Lancashire.
The England all-rounder was cleared to play against Durham at the Riverside just six weeks after knee surgery.
The 31-year-old was handed the ball for the 12th over and had opener Michael Di Venuto caught off his second delivery.
Later on a rain-affected first day, he removed Mitchell Claydon and closed with figures of 12-3-30-2 as Durham limped to 212-8.
Lancashire's decision to play Flintoff was taken in conjunction with the England and Wales Cricket Board.
"It's always a risk when you play, no doubt about that," said Lancashire coach Peter Moores. "But he's sensible, he's done a lot of rehab work and is going very strongly.
"The medical teams at the ECB and Lancashire are very happy and he's got the chance to get some miles in his legs. He looks to be moving very well and there's no pain in that knee at all."
Flintoff was widely expected to be held back for next week's match against Hampshire at Liverpool.
He underwent knee surgery upon his return from the India Premier League, which was played in South Africa, but hopes he might be able to play in the current World Twenty20 proved premature.
That raised fears he might struggle to play a full part in the Ashes series, which begins in Cardiff next month.
Lancashire physio Dave Roberts revealed the level of co-operation with the ECB that brought about Flintoff's return.
"Fred has been working extremely hard on his recovery and fitness and it has been carefully monitored by the England medical staff," said Roberts.
"Dr Nick Peirce, the ECB's chief medical officer, and I have been working closely together and we felt that his knee had sufficiently recovered for him to return to action.
"The ECB medical team have been extremely supportive to me and Lancashire and now it's just a question of Fred getting in some time in the middle and overs under his belt.
"All the work Fred has done, particularly on a recent trip to Portugal when he was pushed really hard, means that he is slightly ahead of schedule in his recovery.
"But he will continue his rehabilitation both on and off the field and hopefully he will be 100% again before not too long."