Intrinsic viscoelasticity increases temperature in knee cartilage under physiological loading.

Area of Science:

• Biomedical Engineering
• Orthopedics
• Tissue Mechanics

Background:

• Cartilage metabolism, including proteoglycan and hyaluronic acid synthesis, is temperature-dependent, with optimal function between 36°C and 38°C.
• Resting human knee cartilage temperature is approximately 33°C, below the optimal range for anabolic processes.

Purpose of the Study:

• To investigate if healthy human cartilage can reach optimal temperatures during physiological loading through viscous dissipation.
• To model and quantify the temperature increase in cartilage due to mechanical loading.

Main Methods:

• Developed a predictive model for cartilage temperature increase based on viscous dissipation.
• Experimentally determined model parameters: energy dissipated (in vitro mechanical testing), heat capacity (differential scanning calorimetry), and heat transfer time constant (in vivo magnetic resonance thermometry).
• Validated the model using data from four volunteers during a 1-hour walking simulation.

Main Results:

• The model predicted a temperature rise in healthy knee cartilage from 33°C to 36.7°C after 1 hour of walking.
• Viscoelastic properties of healthy cartilage are sufficient to induce this optimal temperature increase.
• Degenerated cartilage exhibited insufficient viscoelastic properties, leading to a negligible temperature increase.

Conclusions:

• Intrinsic viscoelastic properties of cartilage can elevate its temperature to levels conducive to proteoglycan and hyaluronic acid production.
• The findings suggest a link between cartilage dissipation, temperature regulation, and joint homeostasis.
• This mechanism may be compromised in degenerated cartilage, highlighting a potential factor in osteoarthritis pathogenesis.