"Restart. How I missed you," the 21-year-old midfielder wrote in an Instagram post on Tuesday alongside a photo of himself training.
Zaniolo was sidelined for seven months in the first half of 2020 after rupturing the anterior cruciate ligament in his right knee.
He then picked up an identical injury to his left knee playing for Italy against the Netherlands in the Nations League last September.
He was operated on in Austria.
Zaniolo hopes to recover to play with Italy in the European Championship from June 11-July 11 with the opening match against Turkey in Rome.
The midfielder has scored two goals in seven games for Italy.
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