Tibet's spiritual leader the Dalai Lama said Saturday he was recovering well from his knee surgery in New York in a video message to his followers marking his 89th birthday.

The charismatic Buddhist exile, celebrated worldwide for his tireless campaign for greater autonomy for his Tibetan homeland, left his adopted home in the Indian hill town of Dharamsala last month for the treatment.

"I am nearly 90 now but I don't feel unhealthy except for the slight discomfort in my legs," he said in a video message published on his website.

"That is inevitable, isn't it, due to the ageing process. Basically I am doing well, so please relax and be at ease."

The Dalai Lama was just 23 when he fled the Tibetan capital Lhasa in fear for his life after Chinese troops crushed a 1959 uprising.

He stepped down as his people's political head in 2011, passing the baton of secular power to a government chosen democratically by some 130,000 Tibetans around the world.

But his advanced age has remained a matter of concern for his fellow exiles, who fear Beijing will name a rival successor to bolster its control over Tibet.

Last month a group of senior US lawmakers including former House speaker Nancy Pelosi met with the Dalai Lama and the Tibetan government-in-exile in Dharamsala, sparking heavy criticism from China.

That visit followed passage of a bill by the US Congress that seeks to encourage Beijing to hold talks with Tibetan leaders -- frozen since 2010.