Thermal evolution of skin temperature during rehabilitation from severe knee injury: A 12-month longitudinal case study of a female junior elite alpine ski racer

• IRT monitored ACL rehabilitation, detecting significant thermal asymmetries. • Injured knee hyperthermia decreased; affected by load, intra-articular injection. • IRT revealed compensatory mechanisms in the noninjured leg. • IRT is a non-invasive monitoring tool for healing, load tolerance, and RTS decision-making. This case study used infrared thermography (IRT) to monitor skin temperature (Tsk) during rehabilitation from a severe knee injury in a 21-year-old female professional alpine ski racer. The study aimed to track knee Tsk changes and detect thermal asymmetries between the injured leg (IL) and the non-injured leg (NIL) over 12 months (72–409 days post-surgery). Initial measurements showed marked IL hyperthermia, with a mean contralateral Tsk difference (ΔTsk mean ) of 1.13 °C that decreased as healing progressed. Although ΔTsk mean declined, the IL consistently exhibited higher Tsk in the anterior (p < 0.001, r = 0.97), medial (p = 0.028, r = 0.73), and lateral (p = 0.002, r = 0.92) regions. Posterior IL regions showed lower Tsk (p < 0.001, r = −0.97), suggesting compensatory mechanisms. Reductions in ΔTsk mean coincided with lower training volumes and an intra-articular anti-inflammatory injection, whereas increases in ΔTsk mean coincided with higher training volumes. By 13.5 months post-surgery, anterior asymmetries returned to healthy ranges. Menstrual cycle status did not affect Tsk at the knees. These results demonstrate region-specific thermographic patterns and support IRT as a non-invasive tool for monitoring knee rehabilitation, assessing load tolerance, tracking healing progress, and supporting return-to-sport decisions. Further research is needed to define objective reference values.