Study Findings
The researchers conducted 3-dimensional gait analysis on runners with PFP and those with aberrant frontal-plane hip and/or pelvis kinematics at baseline were invited to go through gait retraining. In total 12 runners were asked to participate. Data on running kinematics and clinical outcomes of pain and functional outcomes were recorded at baseline, four weeks after retraining and at three months.
The gait retraining took place in one session where the runner’s step rate was increased by 10% using an audible metronome. Then participants were asked to continue their typical running routine while self-monitoring their step rate which they were able to do with a global positioning system smartwatch and audible metronome.
According to the data collected, both running kinematics and clinical outcomes improved at the four-week and three-month follow-ups.
In particular, there were reductions in peak contralateral pelvic drop (mean difference [MD], 3.12˚ [95% CI, 1.88˚-4.37˚], hip adduction (MD, 3.99˚ [95% CI, 2.01˚-5.96˚]), knee flexion (MD, 4.09˚ [95% CI, 0.04˚-8.15˚]), increases in self-reported weekly running volume (MD, 13.78 km [95% CI, 4.62-22.93 km]) and longest run pain-free (MD, 6.84 km [95% CI, 3.05-10.62 km]).
In addition, there were significant improvements in regard to pain in the Friedman test with a post hoc Wilcoxon signed-rank test. Overall, the step rate increased by an average of 11.2% at four weeks.
There were also observable reductions in pain scores on the Numerical Rating Scale (NRS) from an average of 6.2 out of 10 at baseline to 1.0 and 0.3 at four weeks and three months, respectively (X2 = 21.38; p < .01) and on the Lower Extremity Functional Scale the improvement was from 62.3 at baseline to 76.6 at four weeks and 79.7 at three months (X2 = 22.29; p ≤ .01)
Higher Step Rate Changes Hip Adduction, Internal Rotation and Contralateral Pelvic Drop
According to the research team, “After the step rate increase, we observed a 3.12˚ and 3.99˚ reduction in CPD and HADD, respectively, which may offer a mechanical explanation for the improved clinical outcomes seen in this study. These changes are greater than those observed in previous step rate studies, with this being the first study to highlight that kinematic adaptations are maintained at longer term follow-up.”
They added that “it is important to assess for aberrant running kinematics at baseline to ensure that gait interventions are targeted appropriately.”
“It is thought that CPD will give rise to an increase in iliotibial band tension, resulting in lateral displacement of the patella, while HADD would cause the femur to shift medially under the patella. This would result in elevated contact pressure between the patella and lateral facet, leading to elevated joint stress and potentially injury. Therefore, it is possible that the reductions in CPD and HADD after an increase in the step rate would contribute to reduced lateral displacement of the patella and a corresponding reduction in patellofemoral joint stress.”
Reduction in peak knee flexion and increased gluteus medius and maximus muscle activity in late swing phase just before initial foot contact may also reduce the pressure on the patellofemoral joint.
The researchers wrote, “Considering the role that the gluteus medius plays in frontal-plane stability of the hip and pelvis, it is likely that the earlier onset of the gluteal muscles would result in increased neuromuscular stability during the stance phase of gait. This would likely explain the mechanical improvements of reduced CPD and HADD observed in the present study.”
They noted how bigger the improvements were compared to previous step rate studies and how much easier it was for the runners to take control of their retraining. At the four-week follow-up, they all reported that they didn’t have to use the metronome past the first week and were able to easily monitor their step rate with just their GPS smartwatch.
