The focus in recent times on patellofemoral pain or anterior knee pain in runners has all been on the proximal issues despite two randomized controlled trials showing that distal issues (ie foot orthotics) work (see Collins et al & Eng et al). A number of proximal risk factors have been potentially identified and the concept of load reduction on the knee via gait changes and cadence manipulation is the current bandwagon to get on. The superficial discussions on this have been around is it control around the hip or is it control around the knee or is it control of the foot that is most important, when in reality they probably all work together. I talked previously about the paradox I see when it comes to foot orthotics and patellofemoral pain (ie foot orthotics are used to treat “overpronation”; yet almost all risk factor studies show no link between “overpronation” and patellofemoral pain; yet the RCT’s show that when you try to treat “overpronation”, the symptoms improve … go figure!); so I suggested that the potential role of foot orthotics in patellofemoral pain is not to treat “overpronation” but could be to lower the rearfoot inversion moment so the proximal function can do what its supposed to do. This means that the foot orthotics need to lower the rearfoot inversion moment and to do that the foot orthotic is going to need the appropriate “anti-pronatory” design features. Now we have this new study:
The immediate effects of foot orthoses on hip and knee kinematics and muscle activity during a functional step-up task in individuals with patellofemoral pain
Simon Lack, Christian Barton, Roger Woledge, Markus Laupheimer, Dylan Morrisseyemail
Clinical Biomechanics; Articles in Press
Evidence shows that anti-pronating foot orthoses improve patellofemoral pain, but there is a paucity of evidence concerning mechanisms. We investigated the immediate effects of prefabricated foot orthoses on (i) hip and knee kinematics; (ii) electromyography variables of vastus medialis oblique, vastus lateralis and gluteus medius during a functional step up task, and (iii) associated clinical measures.
Hip muscle activity and kinematics were measured during a step-up task with and without an anti-pronating foot orthoses, in people (n = 20, 9 M, 11 F) with patellofemoral pain. Additionally, we measured knee function, Foot Posture Index, isometric hip abductor and knee extensor strength and weight-bearing ankle dorsiflexion.
Reduced hip adduction (0.82°, P = 0.01), knee internal rotation (0.46°, P = 0.03), and gluteus medius peak amplitude (0.9 mV, P = 0.043) were observed after ground contact in the ‘with orthoses’ condition. With the addition of orthoses, a more pronated foot posture correlated with earlier vastus medialis oblique onset (r = −0.51, P = 0.02) while higher Kujala scores correlated with earlier gluteus medius onset (r = 0.52, P = 0.02).
Although small in magnitude, reductions in hip adduction, knee internal rotation and gluteus medius amplitude observed immediately following orthoses application during a task that commonly aggravates symptoms, offer a potential mechanism for their effectiveness in patellofemoral pain management. Given the potential for cumulative effects of weight bearing repetitions completed with a foot orthoses, for example during repeated stair ascent, the differences are likely to be clinically meaningful.
This was a lab based study on the effects of “foot orthotics” on some kinematic and EMG variables in runners with the patellofemoral pain. A strength of the study was it was actually on people with symptoms whereas a lot of other mechanism of action type foot orthotics studies are typically done on a healthy asymptomatic populations, usually undergraduate university students!
Pretty much what the study showed was a change with the use of foot orthotics in the paramaters that are associated with an increased risk for patellofemoral pain.
Nothing in the methods or the analysis jumps out at me as being a problem, except I will re-emphasize that this was an “immediate effects” study in the lab and not a clinical outcome study. Despite that, the authors did conclude that “differences are likely to be clinically meaningful” and I concur.
The only issue I have is the nature of the orthotic used, which I seem to be having a lot of issues with that lately! The study used the Vasyli Easy Fit 3/4 length prefabricated device (this). No rationale was given in the paper for the choice of that foot orthotic with the design features of the type they used, nor is there any description of the device and its design features in the paper. The “anti-pronatory” design features in the foot orthotics that they used are, at best, very weak and have been shown in a static stance study to not change the frontal plane angle of the calcaneus, so I would not classify these as the APFOS (anti-pronatory foot orthoses) that the authors called them. It is interesting to speculate what the results would have been if they used foot orthotics that actually had decent and appropriate “anti-pronatory” design features.
Despite these issues, they did get a result and the results are consistent with the model I hypothesized as to how foot orthotics might work in patellofemoral pain. Foot orthotics are a short to medium term measure and gait modification and exercise therapy is more of a medium to long term measure. Its not one or the other; they work together. The longer term use of foot orthotics is probably going to depend on issues such as the magnitude of the “overpronatory” forces (ie supination resistance); compliance with the gait modification and exercise therapy; and if the tissue can adapt to the loads without the foot orthotics. … and before any fan boy wants to say that you should not use foot orthotics long term because they weaken the muscles (they don’t), please go and read the studies that say the opposite.
As always: I go where the evidence takes me until convinced otherwise … and despite the choice of the foot orthotic, this was a nice study and reinforces that there is not one factor in patellofemoral pain and foot orthotics do have a role in at least the short term to manage patellofemoral pain in runners.
Lack, S., Barton, C., Woledge, R., Laupheimer, M., & Morrissey, D. (2014). The immediate effects of foot orthoses on hip and knee kinematics and muscle activity during a functional step-up task in individuals with patellofemoral pain Clinical Biomechanics DOI: 10.1016/j.clinbiomech.2014.08.005