The 11-times grand slam singles champion, who has not competed since being stunned by Czech Lukas Rosol in the second round at Wimbledon in June, completed a session under the supervision of coach and uncle Toni Nadal at an indoor facility in his home town of Manacor on the island of Majorca.
Nadal, 26, hopes to be back to full fitness in time for the Australian Open in January.
The Spaniard, whose athletic, aggressive playing style places huge demands on his muscles and joints, has been sidelined several times by knee problems during his 11-year career.
His latest injury was diagnosed as a partial tear of the patella tendon and an inflammation of the Hoffa’s fat pad and after the shock defeat at Wimbledon he was unable to defend his Olympic title at the London Games.
As well as the US Open, which he won in 2010 and lost to Novak Djokovic in last year’s final, Nadal missed the season-ending Tour Finals and Spain’s Davis Cup final defeat to Czech Republic at the weekend.