Is forefoot varus related to patellofemoral osteoarthritis?

It is if you believe this study that just appeared in prepublication. However, yet again the editorial and peer review processes let us down as that is not the case at all. The authors and the peer reviewers superficial understanding of the issues have led them to conclusions that are not substantiated and should not have made it to publication.

The study itself is not bad. The authors had access to 25 cadavers and measured the forefoot to rearfoot relationship using the methods that were described by Root et al in 1971 (no problems with that). They also assessed different zones of the patella and femoral trochlea for score them for different levels of cartilage damage (no problems with that). They then looked at the relationship between forefoot position (varus or valgus) to the cartilage damage in the knee and found:

Of the 51% of limbs with forefoot varus, 91.3% had medial and 78.3% had lateral PFJ cartilage damage, compared to 54.6% and 68.2% of those with forefoot valgus. The former also had 3.0 times (95% CI 1.2, 7.7) the odds of medial PFJ damage; no association was found with lateral damage (OR 1.4, 95% CI 0.7, 3.0). Feet in the highest tertile of varus alignment had 3.9 times (95% CI 10, 15.3, p=0.058) the odds of medial PFJ damage as those in the lowest tertile.

I do not have a problem with that.

Where the problems arise is that they were not measuring “forefoot varus”; they were measuring a forefoot that was inverted and the authors superficial understanding of the construct is of concern. As they used Root et al’s (1971) technique to measure the forefoot to rearfoot relationship, they missed those authors definition of what forefoot varus actually it. It is defined as an osseous deformity in which the forefoot is inverted relative to the rearfoot when the subtalar joint is in it defined subtalar joint neutral position and the lateral column loaded. The important point of the definition is that it is ‘osseous’. Forefoot varus is actually very rare, but the authors allegedly found it in 51%. In one of our studies we found it had a prevalence of only 1.6%. What the authors did wrong is they failed to realise that there is the construct of ‘forefoot supinatus’ which is a soft tissue contracture that also is an inverted forefoot and is way more common than the osseous forefoot varus. Given the age of the cadavers, it is probably most likely that most (if not, all) of the feet in the above study were actually a forefoot supinatus.

The difference is crucial and I went into great detail on the differences in my other blog: The effect of forefoot varus on the hip and knee and the effect of the hip and knee on forefoot supinatus …. One is the cause of abnormal pronation of the foot and the other is the result of abnormal pronation of the foot. That is a big difference that has big implications.

I can understand and accept the mechanisms by which a true forefoot varus could be a factor in the pathomechanics of patellofemoral osteoarthritis as that cause of “overpronation” does have affects further up the kinetic change. However, those with patellofemoral osteoarthritis are going to have proximal weaknesses and changes higher up in the kinetic chain that could result in “overpronation” of the rearfoot that over time will result in a soft tissue contracture of an inverted forefoot on the rearfoot (ie a forefoot supinatus).

The authors concluded that:

As forefoot varus may be modified with foot orthoses, these findings indicate a potential role for orthoses in the treatment of medial PFJ OA

Well, no. Using foot orthotics designed for the construct of forefoot varus on a foot that has a forefoot supinatus has the potential for a very negative outcome.

The failure of the authors to distinguish between the osseous and soft tissue versions of an inverted forefoot means the study has limited value. The authors should have looked at the differences and the editorial review process should have picked up on that and not allowed them to make the statements that they did. There is an increasing body of literature failing to make those distinctions. This has to stop.

Lufler RS, Stefanik JJ, Niu J, Sawyer FK, Hoagland TM, & Gross KD (2016). The Association of Forefoot Varus Deformity with Patellofemoral Cartilage Damage in Older Adult Cadavers. Anatomical record (Hoboken, N.J. : 2007) PMID: 27884055

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