Rheumatoid Arthritis: Redness at the Navicular Two Weeks After Delivery
Ms. K, 58, has had rheumatoid arthritis for 15 years. She was fitted bilaterally with functional foot orthoses - 4° medial rearfoot post and 25-mm medial arch fill - for pes planovalgus with forefoot varus. She returns 16 days after delivery reporting burning along the medial arch and a red mark at the right navicular. On exam there is a 2 × 1.5 cm area of intact erythema over the right navicular. Non-weight-bearing, the orthosis sits about 3 mm proud under the arch, and the medial post edge is palpable through the top cover. She is wearing six-year-old walking shoes with the original insole; the heel counter is broken down and the shoe is roughly 8 mm short at the toe. She has worn the orthoses "all day since day one."
1. List the plausible causes of the navicular redness and explain how you would distinguish among them.
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Do not assume the device is at fault. The candidate causes:
- Arch fill too high or too abrupt - the shell shelves up under the navicular in non-weight-bearing and bottoms out in stance.
- Palpable post edge - a hard medial edge concentrating load.
- Shoe failure - a collapsed heel counter lets the foot and orthosis rotate medially, so the arch is driven into the shell; the shoe being 8 mm short pushes the foot forward, driving the navicular into a higher part of the shell.
- Wear schedule - 16 days of full-day wear with no break-in.
- RA-specific tissue - atrophic skin, rheumatoid nodules, vasculitic change; RA skin tolerates pressure poorly regardless of device design.
How to discriminate:
- Mark the red area with a skin pencil, then recheck after 20 minutes of ambulation in the shoes - if the mark transfers to the orthosis top cover, you have located the contact.
- Remove the top cover and palpate the shell under the arch; if the post edge is palpable, that is a device issue.
- Load the shell with the foot and look for shell-through-to-skin contact under the navicular.
- Inspect the shoe: heel counter rigidity, internal length, insole condition.
- Ask how many hours per day and whether the redness appears after a specific duration - that separates a schedule problem from a shape problem.
- Examine the skin for nodules or purpura before blaming the device.
2. Given your findings, what do you change on the device, on the shoe, and in the wear schedule - and in what order?
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Address the shoe first, because the orthosis cannot work inside a broken shoe. The collapsed heel counter means there is no rearfoot control, so the posted orthosis is being asked to control a foot in a shoe that is not holding the calcaneus; and the short shoe forces the foot anteriorly into the shell. Replacing the shoes is not optional here, and it is dishonest to sell device modifications while leaving the root cause in place.
Then the device:
- Reduce the medial arch fill by roughly 3–5 mm and blend the navicular shelf so it is smooth and gradual rather than a ridge.
- Flare and round the medial post edge, and add a soft top cover over the medial aspect so the edge is not palpable.
- Do not simply grind the arch flat - keep enough medial support that the foot is not allowed to collapse, because that collapse is what the device was prescribed for.
Then the schedule: start at 1–2 hours on day one and add about an hour per day, with the instruction to remove the device at the first sign of burning or redness and to check the skin daily.
Sequence matters: skin first (offload and evaluate), shoe second, device third, schedule fourth - and recheck in 7–10 days rather than waiting for the next routine visit.
3. How does the underlying diagnosis of rheumatoid arthritis change your device strategy compared with a mechanical pes planovalgus?
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The mechanical assumptions differ. A posted functional orthosis assumes a deformity that is at least partly correctable and a foot that can tolerate load at the posting site. In RA the deformity is often rigid, the soft tissues are atrophic, and the skin over bony prominences - navicular, first metatarsal head, malleoli - breaks down under loads a healthy foot would ignore.
Practical implications:
- Lean toward accommodative total contact rather than aggressive functional posting. A soft or dual-density shell that follows the foot, with the posting kept modest, is often the better first device.
- Shoe first: a wide, extra-depth shoe with a rocker sole reduces demand at the metatarsophalangeal joints and gives room for a thicker accommodative insert and for deformity.
- Shorter break-in and earlier follow-up than a mechanical foot would require.
- Coordinate: if there are nodules, purpura, or a wound that is not behaving like simple pressure, send her back to rheumatology rather than iterating on the device. Progressive RA deformity also means the device has a shorter functional life; plan for that rather than being surprised by it.