The haelige Admor of Shiputz, Moreinu v’Rabeinu HaGaon HaTzadik Shloimie Rosenbaum of Tzfas, shlita, davens while standing only on his right foot. He tells his many talmidim not to follow his example because they may hurt themselves if they fall over.
The haelige Rebbe says HKB”H watches over him when he davens so that he doesn’t fall over, even at his advanced age.
On Yom Kippur, the haelige Rebbe davens an extended amida during Ne’eila, so at that time a chair is placed under his left knee, helping to support him while he davens. This is the only time during the year this is done.
May we all be zoche to emulate the Rebbe, shlita, and bring Moshiach quickly and speedily. Omein.