Chiellini had to pull out of Italy's crunch FIFA World Cup qualifier against Switzerland on Saturday (AEDT) and returned to Turin for tests.
Juve is waiting to discover how long the Italy skipper will be out of action.
A club statement said: "The diagnostic tests that Giorgio Chiellini underwent this morning at J-Medical showed inflammation of the muscle tendon junction of the left Achilles tendon. His condition will be monitored daily."
Striker Moise Kean completed the entire session with his Juve team-mates on Thursday after recovering from a hamstring injury.
Defender Mattia De Sciglio continues his rehabilitation from a hamstring problem.
The Bianconeri will be eyeing a third consecutive win in all competitions when they face Lazio a week on Saturday,