# Detection of physiological changes in knee cartilage using parametric T2 relaxation maps estimated with a dictionary method

## TL;DR

This study uses T2 mapping to track changes in knee cartilage hydration in athletes after a half-marathon and during recovery.

## Contribution

The study introduces dictionary-matching T2 mapping to detect and monitor subtle physiological changes in knee cartilage.

## Key findings

- Post-run T2 values decreased significantly, indicating reduced cartilage hydration.
- Most compartments recovered within a week, but the lateral condyle showed incomplete recovery.
- Males exhibited more efficient recovery in certain compartments compared to females.

## Abstract

To investigate half-marathon running and recovery effects on knee articular cartilage (KAC) health in athletes, using dictionary-matching T2 maps, to detect changes and recovery patterns in KAC.

Eleven asymptomatic volunteers (4 females, 7 males; mean age 40 ± 5 years, mean BMI 22.7 ± 1.4 kg/m2) completed a fixed-pace half-marathonwere studied. All were right-knee dominant and engaged in regular running. Sagittal T2-weighted Multi-Echo Spin-Echo images at 3 T were used to assess T2 values pre-run, post-run, and one week later for global and compartmental KAC. Recovery programme included low-intensity running, strength training and rest. Repeated measures ANOVA or equivalent non-parametric tests with post-hoc comparisons compared T2 values over time. Separate analyses were conducted based on laterality, gender and anatomical compartments. Significance was set at < 0.05.

Post-run T2 values decreased significantly by 0.9 ms (− 2.0%, p < 0.001), with up to 5.3% reductions in medial tibial (MT) and femoral (MF) compartments. Recovery patterns varied by compartment, sex and laterality. Most compartments returned to baseline within one week; the lateral condyle (LatC) showed incomplete recovery (− 4.7%, Proportional Recovery Index (PRI) = − 0,1); the right knee’s MT exhibited overcompensation (6.3%, PRI = 2.6). Males showed higher baseline T2 values and more efficient recovery in the LatC compared to females (PRI = − 0.1 vs. − 0.4).

Half-marathon running induces reversible reductions in KAC hydration, with most compartments recovering or overcompensating within one week. Dictionary-matching T2 mapping offers a robust approach for monitoring cartilage integrity and guiding individualised recovery strategies.

The online version contains supplementary material available at 10.1007/s00421-025-05898-9.