"I had to retire from the semi-finals of the U.S. Open and this past Monday I was with doctors in Barcelona to review the situation with my knee", Nadal wrote on Twitter.
Rafael Nadal made it official withdrawing from both Beijing and Shanghai events due to his right knee.
It still causes me troubles and I had decided together with my medical and technical team not to participate in the Asian Tour in order to recover the knee the way we have always done in the past.
The 32-year-old, who won the China Open and was a runner-up to Roger Federer in Shanghai in 2017, has struggled with tendinitis throughout his career and has decided in conjunction with his team to extend his time away from the court.
The Spaniard is also the defending champion in Beijing, where he beat Nick Kyrgios in the finals a year ago.
The Spaniard tops the world rankings with 8,760 points, 1,860 ahead of Federer and 2,315 more than in-form Djokovic.
The 17-time Grand Slam champion had to pull out during his semi-final against Juan Martin del Potro in NY and also missed Spain's Davis Cup defeat by France last weekend. He was also the runner-up in Shanghai and had lost the final to eventual victor Roger Federer in 2017.
He also missed Spain's Davis Cup encounter against France last week, in which his side lost to the defending champions.
He also reached the quarter-finals of the Australian Open this year, as well as the semi-finals at Wimbledon.
Nadal's time at the very top of the game looked to have been ended by a wrist injury in 2016 but he has confounded expectations to roar back and win three of his 17 Grand Slam titles.