Tendinous disorders are very common among athletes and the general population. They account for more than 30% of all consultations related to the musculoskeletal system. Tendinopathies are frequently observed in both the upper and lower extremities. In the general population, they have an incidence of:

• 5.5% for rotator cuff tendons
• 7% for lateral epicondylitis
• 1.6% for the patellar tendon
• 4.2% for gluteal tendons
• 2.4% for the Achilles tendon

Tendinous injuries are not well defined. They are highly heterogeneous in nature due to the multitude of potential risk factors that trigger tendinous disorders. It could be said that tendinopathies are tendon pathologies characterized by pain, swelling, and functional impairment. Generally, tendon overload seems to be related to three components (Cook et al., 2016, Thorpe et al., 2015):

1.Change in cell shape.

2.Increase in inflammation markers.

3.Degradation of the extracellular matrix.

Additionally, the presence of pain in tendinopathy could be related to:

• The anatomical and mechanical changes of the tendon.
• How local cells and peripheral nerves react to these changes.

The skin temperature in the area of a pathological tendon can be altered through the nervous system (which can influence blood flow, nociception, and tendon tissue remodeling). The change in blood circulation and tissue metabolism can be directly reflected by the skin temperature (Jewson et al., 2015). Therefore, monitoring skin temperature can be an important measure during this tendinopathy process.

Infrared Thermography and Its Application in Tendinopathies

As a reminder, infrared thermography is a non-invasive and radiation-free technique that captures skin temperature with high sensitivity. This tool has proven useful for monitoring physiological functions related to skin temperature control, making it ideal for evaluating thermal changes associated with tendinopathy processes (Hildebrandt et al., 2012).

Tendinopathies can manifest changes in skin temperature due to inflammation and vascular alterations occurring in the affected tissue. Infrared thermography is particularly effective in detecting these thermal variations, providing valuable information for the diagnosis and monitoring of these conditions.

This was the purpose of the review by Lacerda et al. (2022), which aimed to summarize and analyze the current literature on the use of thermography in the diagnosis of tendinopathy. This review reported that research has shown that infrared thermography can identify significant thermal differences between affected and healthy tendons. The results of Lacerda et al. (2022) demonstrated that thermography showed adequate specificity without heterogeneity among studies in the evaluation of lateral epicondylitis and tendinopathy in the shoulder region. However, some results also showed a significant level of heterogeneity among the studies. This is one of the reasons why Thermohuman always recommends performing thermography under reliable protocols (such as TISEM) and using software for quantitative analysis.

Thermal Responses in Tendinopathies

Practically, we can highlight some characteristics based on the thermal response of tendinopathy:

• Hyperthermic (Heat): This is the most frequent and common response in this type of pathology. The heat response in an injured tendon indicates an active inflammatory process. Inflammation causes an increase in blood flow and local metabolism, which translates into a temperature increase detectable by infrared thermography. This thermal increase is a response to injury by sending more nutrients and immune cells to the area to promote healing.
• Neutral: A neutral thermal response indicates no significant changes in the tendon temperature compared to the surrounding tissue. This may suggest that the tendon is in a non-inflammatory state or that the inflammation is not significant enough to be detected by thermography.
• Hypothermic (Cold): It is uncommon to find a cold response in tendinopathies, as inflammation generally increases local temperature. However, in very advanced chronic cases or with compromised blood supply, a cold response could be observed due to tissue degeneration and lower metabolic activity. The lack of a heat (hyperthermic) response in tendinitis may indicate an insufficient inflammatory response or poor vascularization of the affected tendon.

Infrared thermography is, therefore, a valuable tool for evaluating and monitoring tendinopathies, allowing non-invasive visualization of thermal changes associated with inflammation and aiding in the planning of appropriate treatment.

If you want to learn more and apply thermography in your context, contact us, and we will offer you the best solution.

References:

Cook, J. L., Rio, E., Purdam, C. R., & Docking, S. I. (2016). Revisiting the continuum model of tendon pathology: What is its merit in clinical practice and research? British Journal of Sports Medicine, 50(19), 1187e1191. https://doi.org/10.1136/ bjsports-2015-095422

de Lacerda, A. P. D., de Andrade, P. R., Kamonseki, D. H., Parizotto, N. A., da Silva, A. S. A., de Medeiros, L. B., & de Almeida Ferreira, J. J. (2022). Accuracy of infrared thermography in detecting tendinopathy: A systematic review with meta-analysis. Physical Therapy in Sport, 58, 117-125.

Hildebrandt, C., Zeilberger, K., John Ring, E. F., & Raschner, C. (2012). The application of medical infrared thermography in sports medicine. In An international perspective on topics in sports medicine and sports injury. https://doi.org/10.5772/ 28383

Jewson, J. L., Lambert, G. W., Storr, M., & Gaida, J. E. (2015). The sympathetic nervous system and tendinopathy: A systematic review. Sports Medicine, 45(5), 727e743. https://doi.org/10.1007/s40279-014-0300-9

Thorpe, C. T., Chaudhry, S., Lei, I. I., Varone, A., Riley, G. P., Birch, H. L., et al. (2015). Tendon overload results in alterations in cell shape and increased markers of inflammation and matrix degradation. Scandinavian Journal of Medicine & Sci- ence in Sports, 25(4), e381ee391. https://doi.org/10.1111/sms.12333