There is an increasing number of studies on patellofemoral pain syndrome or anterior knee pain in runners and the affects of gait changes on the biomechanics of it. The British Journal of Sports Medicine just published this:
Take your shoes off to reduce patellofemoral joint stress during running
Jason Bonacci, Bill Vicenzino, Wayne Spratford, Paul Collins
Br J Sports Med doi:10.1136/bjsports-2013-092160
Aim: Elevated patellofemoral joint stress is thought to contribute to the development and progression of patellofemoral pain syndrome. The purpose of this study was to determine if running barefoot decreases patellofemoral joint stress in comparison to shod running.
Methods: Lower extremity kinematics and ground reaction force data were collected from 22 trained runners during overground running while barefoot and in a neutral running shoe. The kinematic and kinetic data were used as input variables into a previously described mathematical model to determine patellofemoral joint stress. Knee flexion angle, net knee extension moment and the model outputs of contact area, patellofemoral joint reaction force and patellofemoral joint stress were plotted over the stance phase of the gait cycle and peak values compared using paired t tests and standardised mean differences calculated.
Results: Running barefoot decreased peak patellofemoral joint stress by 12% (p=0.000) in comparison to shod running. The reduction in patellofemoral joint stress was a result of reduced patellofemoral joint reaction forces (12%, p=0.000) while running barefoot.
Conclusions: Elevated patellofemoral joint stress during shod running might contribute to patellofemoral pain. Running barefoot decreases patellofemoral joint stress.
This study clearly showed that patellofemoral joint stress was lower when the runners were running barefoot compared to running in shoes and is consistent with another recent study that showed knee loads were reduced in forefoot strikers. The mechanism is probably due to the: “reduction in the PFJ reaction force occurred due to the smaller knee flexion angle during the stance phase of running, which decreases the demand on the quadriceps muscles“.
This has potential to assist in the management of patellofemoral pain syndrome, with the following caveats:
- The participants in the study did not have patellofemoral pain syndrome and were healthy, so its not known if the same effect would happen in those with symptoms (though there is no reason to believe that they won’t).
- This was an acute intervention and the participants were novices and not habituated to barefoot running; it is not known if the effects would be there if the runner was habituated to barefoot running. It could be that the novice barefoot runners run somewhat more tentatively and this may or may not have been reason for the reduction in load at the patellofemoral joint.
- The authors did not report on what loads or forces increased in the participants. It is not possible to reduce the ‘load’ in one tissue without increasing it somewhere else. Presumably, as shown by Kulmala et al, the ankle ‘loads’ increased to allow the knee ‘loads’ to be decreased.
As always, I go where the evidence takes me until convinced otherwise, and this is pretty good evidence that we need to be looking at gait changes in those with patellofemoral pain syndrome. Just how much this should be implemented into clinical practice in the absence of an actual clinical trial is still open to debate.
Jason Bonacci, Bill Vicenzino, Wayne Spratford, Paul Collins (2013). Take your shoes off to reduce patellofemoral joint stress during running British Journal of Sports Medicine DOI: 10.1136/bjsports-2013-092160