The 19-year-old is due to remain with the promotion-chasing Foxes at least until the end of January and looks set to feature in the FA Cup tie against Burton on Saturday.
After picking up a hamstring injury on his debut for Nigel Pearson's side at the start of November, the promising centre-back returned to the line-up in impressive fashion during the 6-1 hammering of Huddersfield.
Keane, whose twin brother Will has been sidelined after suffering cruciate knee ligament damage last year, also played for United's Under-21s in their final fixture of 2012 against Morecambe.
Meanwhile, Jesse Lingard has returned to Old Trafford after making five substitute appearances during his stint in the East Midlands.
* Born on 11 January 1993
* Twin brother of Will
* England Under-19 international
* Two starts and a substitute appearance for United
* Unused sub at Anfield for the FA Cup tie with Liverpool last year
* Reserves Player of the Year in 2012
* Made Championship debut for Leicester in November
* Played at right-back in the FA Youth Cup-winning team of 2011