A safe method for detecting cartilage injury at the cellular level in live tissues is highly sought after, as current methods involve cartilage sectioning or the use of dyes that are not safe for patients. A study now provides proof-of-concept that quantitative multiphoton microscopy, with FDA-approved sodium fluorescein, can safely be used to detect early, minor cellular-scale cartilage injury after compressive loading damage (in mature equine distal metacarpal or metatarsal osteochondral blocks).