Quadriceps femoris muscle contracts eccentrically during the stance phase of running till the beginning of propulsion when the knee reaches the highest level of flexion. Limited dorsiflexion in the ankle joint is associated with a compensatory increased knee flexion, tibial inversion, and foot pronation during the stance phase of running. Theoretically, these compensatory mechanisms might cause increased stress on the quadriceps femoris muscle attachment to the tuberositas tibia. This study is aimed at evaluating a possible relationship between limited dorsiflexion of the ankle and the occurrence of Morbus Osgood Schlatter (MOS) in sports-active children. Forty-five children, including 40 boys (mean age 13 years, range 11-14) and 5 girls (mean age 12 years, range 10-12) with the clinical diagnosis of MOS, were studied. Dorsiflexion angle (DFA) of less than 10 degrees was found in 37 boys, whereas 3 of them had a DFA of more than 10 degrees . All five girls had a DFA of less than 10 degrees . In conclusion, limited dorsiflexion of the ankle joint might be of significant importance for MOS. Further studies are warranted to evaluate the cause-effect relationship.