Root based biomechanics and the evidence for it has been the topic of debate for some years now. While it is increasingly apparent that the Root Model of “normal” and “abnormal” is not well substantiated by research there are plenty of clinicians, worldwide, who use this model, and their patients get better! This month we look at one of the papers which challenges some of the Root principles.
Challenging the foundations of the clinical model of foot function:
further evidence that the root model assessments fail to appropriately classify foot function
Jarvis. H., Nester. C., Bowden. P. & Jones. R. (2017).
Journal of Foot and Ankle Research. 10 (7)
This paper aimed to investigate the relationship between foot deformities and kinematic compensations associated with the Root Model of Biomechanics. Static Root based biomechanical assessments were carried out on 100 symptom free participants to classify 5 foot deformities. Statistical tests then compared foot kinematics between feet with and without foot deformities. “None of the deformities proposed by the Root Model were associated with distinct differences in foot kinematics during gait when compared to those without deformities or each other”
What it all means:
At the time of publication, this paper was one of the largest and comprehensive studies to investigate the Root Model and its results support the growing wider body of evidence. This essentially means that assessments in the Root protocol which define foot deformities have no relationship with foot kinematics during gait. “This undermines their validity as the basis for identifying normal and abnormal foot function and as the basis for foot orthotic prescription”.
- Assessments included were NCSP, RCSP, range of dorsiflexion at the ankle joint, range of dorsiflexion at the 1st MPJ, position and range of motion of the first ray, and frontal plane position of the forefoot to rearfoot
- Foot Posture Index was also assessed for comparison purposes
- A 6 segment model (leg, calcaneus, midfoot (navicular and cuboid), lateral forefoot (fourth and fifth metatarsals), medial forefoot (first metatarsal) and hallux was used to characterise foot kinematics.
- The assessment protocol advocated by the Root Model is no longer a suitable basis for professional practice
- Clinicians should stop using the following during clinical assessments as a means of defining the associated foot deformities:
- Sub-talar neutral position
- Non-weight bearing range of ankle dorsiflexion
- First ray position
- Forefoot alignments and movement
Putting it into practice:
- To play Devil’s advocate….. clinicians have been using Root principles for decades & patients have got better! However, it is likely that they did not get better for the reasons originally proposed. Critics may also suggest that Root Theory doesn’t state that patients with abnormal foot positions are symptomatic or that they are likely to become so. However, under the Root Model it has been accepted that if a symptomatic patient has an abnormal foot position, clinicians should address the resultant “compensations”. Essentially, we now know that foot orthoses have an effect on forces and moments but they are not so predictable at changing kinematics in gait. All in all, we need to keep in mind the bigger picture and remember what works in a clinical setting.
- While this paper legitimately questions the use of Root based assessments, many clinicians question what to replace them with, particularly regarding procedures such as what position to cast the foot in. The issue here is that we still need a baseline to start from in the absence of research to propose a better method.
- Many clinicians use the non weight-bearing ankle joint ROM test and this has aided them to make sound clinical judgements for treatment plans. However, it is imperative that we do not ignore the evidence against it so try adding other tests to your patient assessment to help evaluate ankle joint ROM like the Lunge Test (which does have evidence to support its use).
- There are countless more points and discussions which can be made from this paper which is beyond the scope of this overview. Hopefully it will provoke debate and discussion and prompt clinicians to review and justify their current practices (whether they change them or not).