MADRID - Rafa Nadal has passed the latest medical tests on his injured knee, the Spanish tennis federation (RFET) said on Wednesday as the world number four confirmed he would return after more than seven months out at the Brazil Open next month.

"The tests confirm that Rafa's recovery is proceeding favourably," RFET doctor Angel Ruiz-Cotorro said.

"Medically speaking we are in the final stages and the results were very satisfactory and the return to the circuit is expected to proceed according to plan," he added.

Spain's Rafael Nadal gestures between television interviews, during which he detailed reasons for pulling out of the US Open, in Palma de Mallorca, on the island of Mallorca, Aug 17, 2012. [Photo/Agencies]

Nadal was due to make his competitive comeback at last month's exhibition tournament in Abu Dhabi that is not part of the ATP Tour.

The 26-year-old won the event in 2010 and 2011 but withdrew on Dec 25 saying he had a stomach virus and later pulled out of this month's Australian Open.

He has not played since June when he suffered a shock defeat in the second round of Wimbledon to Czech Lukas Rosol.

He was subsequently diagnosed with a partial tear of the patella tendon and inflammation in his left knee and was unable to defend his Olympic title at the London Games.

The 11-times Grand Slam singles champion also missed the US Open and the season-ending World Tour championships before returning to the practice court on Nov 20.

Nadal, who is projected to drop to number five when the rankings are updated after the Australian Open, said on Wednesday he was looking forward to the Sao Paulo event, played indoors on clay and which starts on Feb 11.

"Here you see me on a clay court preparing for the tournament in Sao Paulo," he said in a message posted on You Tube.

"I am very excited about returning to play in Brazil after so many years," the French Open champion added.

"The last time was in 2005 and I have some fantastic memories. I want to give a huge thanks to the organizers for inviting me to participate in the tournament and I hope to see you there very soon."