Weak ankles are not an unknown symptom of advancing age, but they make news when they belong to a statue – specifically, Michelangelo’s 510-year-old David.
According to tests carried out by researchers at Italy's National Research Council (CNR) and the University of Florence, the statue is at risk of crumbling under its own weight due to its weak ankles.
Alarm bells sounded after researchers carried out a series of centrifuge tests on small-scale plaster replicas of the marble masterpiece. The experiments revealed that, under high-stress conditions, the statue would break along small cracks currently visible in the left ankle and in the lower part of the carved tree stump supporting the right leg.
The cracks "were first detected between 1852 and 1872 and nowadays they are more extensive than in 1872," Giacomo Corti, a researcher at CNR's Institute of Geosciences and Earth Resources, and colleagues wrote in the Journal of Cultural Heritage.
Although they have been covered up with plaster over the years, the hairline cracks tend to reappear. They do not indicate an imminent collapse, but could prove devastating in the event of an earthquake.
The 5,572-kg marble statue is at its most stable when vertical, but would break under its own weight if standing at an inclination of 15 degrees or higher, the tests suggest.
In such a scenario, the statue's pose and poor quality marble would contribute to the collapse.
Michelangelo carved David from a single block of marble that two other sculptors, Agostino di Duccio and Antonio Rossellino, had discarded due to an imperfection.
On Sept. 8, 1504, the towering sculpture, acclaimed for its depiction of male physical perfection, was displayed beside the main doorway of the Piazza della Signoria in Florence.
Representing the biblical hero who killed Goliath, the sculpture marked a watershed in Renaissance art and established Michelangelo as the foremost sculptor of his time at the age of 29.
The statue remained in its original location, at the mercy of the elements, until 1873, when it was moved to its present location in the Galleria dell'Accademia.
According to the researchers, the micro fractures currently visible on David are the result of a long-lasting, small forward inclination of about 5 degrees during the statue's time in Piazza della Signoria between 1504 and 1873.
"The research confirms previous hypothesis and could help in the preservation of this masterpiece," Cristina Acidini, superintendent of Florence's museums, said.
She reassured that the cracks do not pose an immediate threat.
"Since 2001, David's micro fractures are constantly monitored and no variation has been recorded so far," Acidini told Florence's daily La Nazione.