Pietersen, 33, missed the two-Test series against New Zealand this year after damaging his knee in February and has been troubled by a calf problem since the second Ashes Test at Lord's.
"Kevin Pietersen had a precautionary scan on his right knee today as part of an ongoing monitoring process following the bone bruising injury that occurred in February," the ECB said in a statement on its website (www.ecb.co.uk).
"Kevin remains available for selection for the fifth Ashes Test and will continue to receive treatment on his right knee as part of his rehabilitation programme over the course of the remainder of the series and beyond."
England team director Andy Flower refused Pietersen permission to make a rare appearance for his county Surrey in the Twenty20 Finals this weekend.
England lead the Ashes series 3-0 going into the final match at the Oval starting next Wednesday.
Pietersen has scored 276 runs in the first four Tests, including one century and one fifty.
Image: Kevin Pietersen
Photograph: Stu Forster/Getty Images