A mechanical diagnostic probe is used to determine the thickness of articular cartilage, so that any degeneration in the articular cartilage can be detected at an early stage. The probe advantageously allows for calibrating the speed of the ultrasound in situ thereby allowing for more accurate measurements of the tissue thickness. The probe also can be used to monitor the condition of the cartilage after surgery and/or after or during physical rehabilitation of the cartilage. The probe is comprised of a probe handle and a probe, which is comprised of an ultrasonic transducer, strain-gauges, and a linear displacement actuator. A predetermined displacement then is applied to the indenter tip and a computer program is then used to analyze the results.