Aim Running has become a popular physical activity, with a continuously growing number of participants in all around the world in order to maintain cardiovascular fitness and mental health. Therefore, it is a public health issue to research the short and long term effects of running over the knee joint. During the last decade, with the advancements in the quantitative magnetic resonance imaging (MRI) techniques, MRI is being widely used in the field of exercise and its effects to the joint cartilage. This study was designed to determine the effects of 30 minutes heart-rate controlled (80% of the maximal heart rate) running exercise on a treadmill to the dominant and non-dominant knees with using of 3D turbo spin echo MRI technique.

Methods Twenty-two healthy subjects, aged 18–35 years, participated in the study and both knees MRI views were obtained after 24 hours of rest. Second MRI evaluation was performed for both knees immediately after running exercise at the following day. The measurements of T2 signal intensity, mean pixel values and thickness of the knee joint were taken in patellofemoral and femorotibial joints.

Results Significant decrease in mean pixel values of T2 signal intensity in both dominant and non-dominant knees’ tibia and femur cartilage after running compared with the resting values was detected (p < 0.001). The most obvious decline was seen in the medial tibial plateau of the dominant knee (−10.6%).

Conclusion It was speculated that decrease in T2 values suggests shifting of the cartilage water content with running activity. Greater decreases in the medial tibial plateau cartilage indicates greater load sharing by these areas of the joint during running exercise.