The Gunners host title rivals Leicester City at the weekend.
The Gunners have been title contenders for most of this season, with a strong start to the campaign having seen them challenging at the top.
A disappointing run in January in which they went four games without a win, failing to score in three of them, had threatened to ruin their chances as the season nears the business end.
However, they returned to winning ways with a 2-0 victory over Bournemouth last weekend, and Keown says they now need to pull a big result against one of their rivals out of the bag if they are going to win the title.
“It was crucial that Arsenal because they have a massive month ahead of them, and they needed to restore some belief and find some momentum,” he told BBC Sport.
“The Gunners are going strong in three competitions - the Premier League, FA Cup and Champions League - and have a big opportunity to land at least one trophy.”
“If the Gunners are going to win the title again this year, then they have got to pull a big result out of the bag sooner or later. The next few weeks give them that chance to get a season-defining win of their own.”
If Arsenal are to secure that big win they need to secure the title, then this weekend is the perfect opportunity to do it.
They host leaders Leicester City at the Emirates, in a game being billed as crucial to both sides' hopes of winning the Premier League this season.
Given that the Foxes beat Manchester City 3-0 last weekend, a win for the Gunners would certainly show their credentials and perhaps give them the momentum to go on and make first place their own.