Ankle sprain is one of the most common injuries in sports involving changes of direction or landings. Thermography analysis will allow a thermal pattern to be developed according to the response of the athlete and the injury.

The ankle joint is designed to allow mobility of the tibia and fibula over the talus during gait phases, which is crucial for the functional movement of the lower body. Limitations in the mobility of this joint have been shown to be associated with increased lower locomotor system injuries, as sprain, by tests assessing the degrees of active ankle dorsiflexion when the foot is fixed on the ground. (Clanton, et al. 2011; Hoch, et al. 2012)

Sprains in sports such as football or basketball are one of the most prevalent injuries, for example in a recent review by Torres-Ronda (Torres-Ronda et al 2022) the authors found that the second region with the highest number of injuries and the longest time of absence was the ankle. Furthermore, if we look at football, the study by Noya et al (Noya, et al 2012) showed that ligament injuries were the second most common cause of injury followed by muscle injuries (182.1 days off work per team per season). At the ligament level, the most affected region was the external lateral ligament of the ankle, with a frequency of 3.7 injuries per team per season. This research is in line with that of Walden et al (Walden et al 2005) who show that the highest percentage of ligament injuries occur in the ankle joint, with 51% of all injuries. Of these, 73% occur in the anterior peroneal-astragalus ligament.

From a thermographic perspective, when there is an injury to the ligamentous tissue, what we find recurrently is a hyperthermic signal produced by the inflammatory response of the tissue. This response is followed by a cascade of events to cause tissue healing. One of the main objectives of this inflammation is to reduce the mobility of the area in order to preserve unaffected tissue until the area is repaired (Blamson et al 2021).

Depending on the degree of involvement, sprains can be categorized as follows (Garzón-Alvarado et al 2012)

• Grade I, manifests minimal loss of function, minimal pain, no fiber rupture, no ecchymosis (hemorrhage into the skin and subcutaneous tissue greater than 1 cm3 ), no weight-bearing difficulty, mechanically the tissue suffers deformation, however, it is preserved within the physiological range of the stress-strain curve.
• Grade II shows partial fiber rupture, some loss of joint function, pain, ecchymosis, and weight-bearing difficulty. This injury arises because the magnitude of the load is such that it exceeds the peak tensile strength of the ligament, although it does not always reach its breaking strength. Thus the ligament is severely weakened, sometimes remaining physically intact and retaining some mechanical strength.
• Grade III shows complete rupture of the fibers, severe loss of joint function, severe pain and swelling, ecchymosis and there is always difficulty in weight-bearing. In this injury, the load exceeds the peak tensile strength of the ligament until it reaches its breaking strength.

As has been seen, the injury, according to the clinical signs and symptoms, can be classified into three grades according to its complexity. Thus, the thermal response will vary according to the severity of the injury, among other factors.

An analysis of the ThermoHuman database (unpublished data) with more than 32 athletes injured with an ankle sprain reveals a hyperthermic response of the region that is maintained overtime for more than 100 days, similar to what is described in the literature as healing time.

Figure 1. Thermal response after suffering an ankle sprain (mean values of 32 injured athletes with different severities).

As we have seen, one of the most important factors is the degree of severity of the sprain, as it will produce different signals, while if the sprain is mild, the fibroblasts will act in the remodeling phase, if the sprain is more severe, the inflammation will be greater and the growth factors and cytokines will act in the healing process (Garzón-Alvarado, et al 2012).

From a thermal point of view, it has been shown that the inflammatory response is related to the hyperthermic response, the more severe the ligament injury, the greater the inflammatory response.

The ThermoHuman team is working to establish patterns of thermal response associated with the different injuries in order to establish an ideal post-injury follow-up model as shown in figure 1. The idea is that it will serve as a control chart in the follow-up of the injury and a guideline for recovering homeostasis.

We leave you with these three cases of injury that can serve as a monitoring tool in the follow-up of an ankle sprain:

These tools help to understand the physiological processes of the player and improve the analysis of the internal training load. This is especially relevant when work protocols are established based on thermography information, which impliesgreater savings than the economic cost of its implementation.

References

Clanton, T. O., Matheny, L. M., Jarvis, H. C., & Jeronimus, A. B. (2012). Return to play in athletes following ankle injuries. Sports Health, 4(6), 471-474.

Hoch, M. C., & McKeon, P. O. (2011). Normative range of weight-bearing lunge test performance asymmetry in healthy adults. Manual therapy, 16(5), 516.

Torres-Ronda, L., Gámez, I., Robertson, S., & Fernández, J. (2022). Epidemiology and injury trends in the National Basketball Association: Pre-and per-COVID-19 (2017–2021). PLoS one, 17(2), e0263354.

Noya J, Sillero M. Incidencia lesional en el fútbol profesional español a lo largo de una temporada:
días de baja por lesión. Apunts Med Esport. 2012. doi:10.1016/j.apunts.2011.10.001

Walden M, Hagglund M, Ekstrand J. Injuries in Swedish elite football: a prospective study on injury definitions: Risk for injury and injury pattern during 2001. Scand J Med Sci Sports. 2005;15:118---25.

Bramson, M. T., Van Houten, S. K., & Corr, D. T. (2021). Mechanobiology in tendon, ligament, and skeletal muscle tissue engineering. Journal of Biomechanical Engineering, 143(7).

Garzón-Alvarado, D. A., Cárdenas Sandoval, R. P., & Vanegas Acosta, J. C. (2012). A mathematical model of medial collateral ligament repair: migration, fibroblast proliferation and collagen formation. Computer methods in biomechanics and biomedical engineering, 15(6), 571-583.

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