Modeling The Total Force At The Knee Joint During A Fatiguing Run

Running is associated with a high incidence of injuries. Neuromuscular fatigue is considered a risk factor, suggesting that the body in a fatigued state is less able to attenuate impact forces sufficiently, which leads to overloading and injuries.

PURPOSE: To model total knee force, consisting of reaction and muscle forces, using an OpenSim model and free body diagram before and after a fatiguing run to get insight into potential overloading of the knee during running.

METHODS: 7 recreational rear-foot striking runners (3F/4M, running >10 km p/w for >1 year; uninjured
RESULTS: Total force inside the knee (total force tibia - femur) during stance have a tendency to increase after a fatiguing run: the maximum force on the knee increased from 21.5 ± 2.3 BW to 23 ± 2.5 BW in a fatigued state (paired t-test, p = 0.23). Main cause was the increase of maximum extensor muscular contractions (15.2 ± 1.3 BW to 16.6 ± 2.2 BW, p = 0.09) to increase overall knee load, flexor muscular contractions and JRF did not significantly change between non-fatigued and fatigued state (fig. 1).

CONCLUSIONS: Knee load in a fatigued state has a tendency to increase after a fatiguing run, which results in a repetitive increased force on the knee that can eventually lead to overloading. These results indicate that running in fatigued state may cause damage to biological tissues in and around the knee which results in injuries.