The Swedish striker revealed on social media that he has played the last six months of the season without an anterior cruciate ligament (ACL) in his left knee -- the strong band of tissue that connects the thigh bone to the shin bone and the knee joint.
"Swollen knee for six months," Ibrahimović said in a post published to his verified Instagram account on Thursday. "I was only able to train with the team 10 times in the last six months."
"Took more than 20 injections in six months. Emptied the knee once a week for six months. Painkillers every day for six months. Barely slept for six months because of the pain. Never suffered so much on and off the pitch."
The Rossoneri won 3-0 against Sassuolo to clinch their first Serie A title in over a decade, ending the season on 86 points -- two points ahead of runners up Inter Milan.
"I made something impossible to something possible. In my mind I had only one objective, to make my teammates and coach champions of Italy because I made them a promise. Today I have a new ACL and another trophy," Ibrahimović added.
Ibrahimović's post came hours after AC Milan announced that he had undergone successful knee surgery in Lyon, France on Wednesday.
"AC Milan announces that Zlatan Ibrahimović underwent an operation on his left knee carried out by Dr Bertrand Sonnery-Cottet, with the Club's Medical Director Stefano Mazzoni in attendance, at the Hôpital Jean Mermoz in Lyon," the club said in a statement.
"The arthroscopy had been planned for a while to definitively resolve the joint's instability through the reconstruction of the anterior cruciate ligament, with lateral reinforcement and meniscus reparation."
"The operation was a complete success and the prognosis is estimated between seven and eight months," the statement added.
Since rejoining the Serie A side in December 2019, Ibrahimović has garnered several accolades including passing 500 career goals in February 2021, and become one of the few quadragenarians who have competed in Serie A.
Despite his injury, Ibrahimovic played 23 out of 28 league games last season and scored eight goals, according to the Milan website.
But given that his contract ends this summer, and he is likely to miss the first half of the 2022/23 season following his operation, Ibrahimović's future at the club remains uncertain.
"I'm in a situation now where I'm close to the goal line ... so I'm a little bit panicking," he told ESPN earlier this month.
"Because when it stops, what do you do? I know I can do a lot of things, I will have offers from all over the place. But the adrenaline I get on the field, I will never get that (from) something else."