Martinez started Argentina's stunning opening group stage loss to Saudi Arabia - where he had a couple of goals disallowed for offside - and also their win over Mexico.
But the Inter Milan player only came on in the final minutes against Poland in their last group match and against Australia in the last 16, prompting local media to raise questions about his physical condition.
"Lautaro has been taking injections because he has a lot of pain in his ankle," Camacho told Argentine radio station La Red.
"He's working hard to make that pain go away, and as soon as that happens, he'll be flying on the pitch. Martinez is a top player in the world.
"He is very strong in the mind, but the goals that were disallowed against Saudi Arabia were hard moments for him."
Martinez has seen his starting spot in the Argentine line-up taken by Manchester City striker Julian Alvarez (22), who has scored two goals so far.
"The competition makes him (Martinez) and Julian stronger, because contrary to what you might think, they are good for each other," Camacho added.
Argentina take on the Netherlands in the quarter-finals on Friday.
