Plantar heel pain is the most common presentation of musculoskeletal pain to most podiatrists in private practice. There is still much debate on the cause of pain and the term ‘plantar heel pain’ probably encompasses several diagnoses. For the sake of this blog post, we’ll focus primarily on what is commonly referred to as ‘plantar fasciitis’ or ‘plantar fasciopathy’. This presents with the classic post-rest pain (or post-static dyskinesia). Note – if the patient doesn’t have post-rest pain, I’d be considering other differentials. We know this condition affects more females than males, is more likely to occur in adults over 40 and is more likely in overweight or obese people.
If you’ve recommended custom foot orthotics be part of your treatment plan, are there prescription parameters you should consider? Whilst I’m strongly against a cookie-cutter or recipe type approach to treating any pathology, there are certainly some prescription parameters to consider for plantar fasciitis.
Before we get to those prescription parameters though, I think it’s important to take a step back and think about what the likely contributing factors are. In plantar fasciitis, I think there are a couple of key things which contribute to the development of this condition:
- Increased strain on the central band of the plantar fascia, and
- Increased ground reaction force on the heel.
We know that increased STJ pronation alone doesn’t lead to plantar fasciitis. If that was the case, then only people with a pronated foot type would develop this problem. We know that this problem can occur in any foot type – supinated, neutral or pronated (basic classifications, but you get the point!).
So if we need to look beyond the STJ as a mechanical explanation, what else could be contributing? Potentially what can occur is: either a forefoot valgus or STJ pronation leads to 1st ray dorsiflexion and inversion – this causes the midtarsal joint to supinate, eccentric contraction of flexor hallucis brevis and abductor hallucis and a lowering of the MLA – these can all increase the strain on the plantar fascia.
In terms of treatment then, I think one of the best papers to give us a clue here, was Kogler’s 1999 cadaveric study. Kogler and colleagues took 9 cadaveric specimens and inserted load transducers into the plantar fascia. Each specimen had an axial load through the tibia of up to 900 Newtons exerted through it. 6-degree wedges were applied in different combinations under medial and lateral rearfoot and forefoot and the load was measured through the plantar fascia. It was found that wedge under the lateral forefoot (forefoot valgus wedge) significantly decreased load through the plantar fascia, whilst a wedge under the medial forefoot (forefoot varus wedge) significantly increased strain through the plantar fascia. Rearfoot wedging alone did not produce a significant change in plantar fascia strain.
When it comes to orthotic prescription then, what are some of the things you should consider?
How to take the impression:
- STJ in neutral with the MTJ fully pronated (reduce forefoot supinatus by plantarflexing the first ray). Capturing a forefoot valgus in the cast/scan provides a better outcome, rather than trying to ‘manufacture’ it in the design process!
Positive cast or CAD modifications:
- Pour vertical
- Plantar fascia accommodation (3-4mm), blended so as not to cause irritation on the medial or lateral margins of the accommodation
- Potentially a minimal arch fill design if the foot mechanics warrants it
- Accommodations for any fibromas or tears
- Avoid medial heel skives (this can increase ground reaction force at the medial calcaneal tubercle)
- Intrinsically post a forefoot valgus if captured in the cast/scan – this is critical!
- Semi-rigid material, appropriate for foot mechanics, patient size and activities
- Heel apertures and pads
- Deep heel cups (>16mm)
- Intrinsic forefoot valgus
- Potentially extrinsic forefoot valgus wedging
Whilst we recommend you consider these prescription variables when prescribing orthotics for plantar fasciitis, it’s important to remember not to take a cookie cutter type approach to dealing with any pathology and to treat the individual in front of you.
Kogler GF, et al. The influence of medial and lateral placement of orthotic wedges on loading of the plantar aponeurosis. J Bone Joint Surg Am. 1999 Oct; 81(10):1403-13.