Sillero and collaborators (2015) showed us that most injuries are related with a warmer asymmetry. That is to say that regions involved in acute injury have hyperthermia, on average of 0,5ºC.

Nevertheless, it does not mean that every single injury or issue is hotter. Indeed, one of the most fascinating points about thermoregulation (and therefore infrared thermography) is that depending on the injury/pathology the thermal pattern can be both, hyperthermia or hypothermia, hotter or colder than the healthy bilateral region (Fernández Cuevas 2019).

Hyperthermia or warmer areas are related with inflammation, overuse or an increase in the metabolic activity of the tissue underneath the skin, creating a thermal asymmetry related to pathologies/injuries as bone fracture, sprain, contracture, arthrosis, tendinitis, etc. (Sillero et al. 2015).

On the other hand, hypothermia or colder areas might be related to inhibition, compensation or deficit of physiological/metabolism activation. This pattern is strongly related to pathologies/injuries as nerve system issues, vascular system issues bad cicatrization process, etc. (Sillero et al. 2015).

Hyperthermia can be as important as hypothermia. Infrared thermography might be useful, depending on the thermal pattern (hot or cold) to understand which thermal process is going on in the affected region and therefore to help the diagnosis process.

References:

Sillero-Quintana, M., Fernández-Jaén, T., Fernández-Cuevas, I., Gómez-Carmona, P. M., Arnaiz-Lastras, J., Pérez, M.-D., & Guillén, P. (2015). Infrared Thermography as a Support Tool for Screening and Early Diagnosis in Emergencies. Journal of Medical Imaging and Health Informatics, 5(6), 1223-1228. doi: 10.1166/jmihi.2015.1511

Fernández-Cuevas, I. (2019). Aplicación de la termografía infrarroja para la prevención, seguimiento de lesiones y apoyo al diagnóstico en el deporte y la salud. Paper presented at the 15º Congreso Internacional de Ciencias del Deporte y la Salud, Pontevedra, Spain.