Don't miss this flat foot condition in your patients... with tips on how to recognise it.

Flat feet don't usually hurt, especially in children. But if you notice a one-sided, worsening, painful flat foot in an adult, think.... Acquired Adult Flat Foot!!

How does it present?

Gradual onset (usually) of medial ankle pain, and sometimes lateral ankle pain (as the condition worsens)
Patient will be unable to do a single leg heel raise (see picture below) due to posterior tibial muscle and tendon dysfunction
Usual age- 45 to 65, women 4x more likely to get. Risk increased with diabetes, hypertension, and obesity.

Tests to diagnose?

Single leg heel raise (inability indicates post tib dysfunction)
Hubschers maneuver (indicates midfoot collapse and dysnfuction in the windlass mechanism)
Xray (to show joint position and disease) and MSK ultrasound (to assess the posterior tibial tendon integrity), although clinical assessment can identify the level of deformity

How to fix it?

This is not a condition to be complacent with! Depending on the stage of deformity, different degrees of immobilisation, orthotic support, and rehabilitation therapies will be needed. Physio's take note- these patients always will need custom orthotic therapy. Do NOT give heel raise exercises and cross your fingers and hope for the best! It will get worse, they will not be happy with you, and they will need a more corrective orthotic and possibly surgery.

At Pioneer Podiatry (here's the plug...) we specialise in treating this condition, including custom AFOs which are very effective in treating this condition. The good news is about 50% of all AAFF patients treated with custom AFOs are symptom free after 12 months, and can often go without the brace for most activities.

This article is really a very brief overview, so if you've got a hankering for the details of how to assess and treat this condition, have a squizz over at our Clinical Practice Guideline in our Referrers Portal. It's free, instant assess to clinical tests with video demonstrations, patient handouts for this condition, and treatment protocols to help you give the best treatment and advice to your beloved patients. Find it here.

Have a great day! Keep being awesome.

What is the plantar plate?

Isn’t that the thing you put under your pot plants to catch the water? Well, NO! It’s way more interesting than that, and it’s probably the most underdiagnosed cause of forefoot pain in most primary care clinics.

The plantar plate is the fibrocartilagenous thickening of the metatarsophalangeal joint, under the foot, just behind the toes. It is a complicated little piece of anatomy, which needs to do several big jobs at different stages in the gait (walking) cycle. If you’re interested, this includes enabling the windlass mechanism of the foot to engage and resist medial arch collapse in mid stance and propulsion. If that doesn’t make sense, I want you to remember just one thing… it attaches to and is made from the same fibres as the plantar fasciia. This is a big deal, and I’ll explain why later.

Tears of the plantar plate happen all the time, and can occur at any of the metatarsophalangeal joints. It has various pseudonyms, including floating toe syndrome, crossover toe, and predislocation syndrome. It is most common in the 2nd MP joint, as it’s the longest metatarsal, and it has some inequalities in the attachments of the little deep muscles in the foot (lumbricals and interossei). Any abnormal forefoot loading patterns, like that seen in HAV (bunions), will hugely increase the compression and longitudinal tension stress on the 2nd MP joint. The tear is generally just past the joint, at the base of the first bone on the toe (phalange). (1)

So, what does it look like?

Normally, pain right in the area just under the 2nd toe joint (2nd MPJ). Often your patient will describe a feeling of swelling under this area, like walking on a lump. If it’s recent and severe, you’ll see swelling in the forefoot and toe, and often an immediate wonky toe (not a technical term!). To demonstrate this wonky toe effect, get them to stand barefoot. If there is excessive space immediately obvious between the 2nd, 3rd or 4th toes, think plantar plate tear.

One trick- your patient may complain of neural type symptoms (burning, numbness etc) in the affected toe. This is due to localised swelling annoying the intermetatarsal nerve. You might be tempted to think it’s a mortons neuroma. Don’t be tricked by this one!

How to test

Grab the toe and dorsiflex it (point it up towards the roof, if they’re sitting!). This will aggravate an acute tear. There is also a test called the modified Lachmans test, when the toe is dorsally translocated (pulled upwards, again, in a sitting/ supine patient). If it moves more than 2mm/ 50%- think plantar plate tear. Also, the wonky toe sign when standing, which I mentioned before.

Now- what does this injury have to do with plantar fasciitis? In short, they very often occur together, because whatever increasing stress in the plantar fasciia immediatly has to increase stress in the plantar plate. Anatomically, the plantar plate IS part of the plantar fasciia. So, if you see one, look for the other.

Scans/ studies?

An ultrasound can be helpful to visualise the tear in the plantar plate. MRI can show tears, and assess how bad they are. We do not routinely image this injury however. Xrays will not be helpful, except to exclude other causes of pain in this area (Frieburgs infarction, for example). (2)

Treatments?

Straight away, icing (first 3 days in acute/ athletic cases), NSAIDs, and some relative rest to reduce tissue stress to the joint. Moon boots and cam walkers are a great option first 3-4 weeks. Strapping to assist plantar flexion of the toe can be fantastically successful for some. Flexible tapes, such as Rock tape/ Kinetic tape, are the best for this.

Longer term, you need to reduce the tissue stress to allow normal gait and reduce re-injury. Orthotic therapy is very useful, as long as it’s done right. Us podiatrist get excited by this, and we’ll throw around words like plantar metatarsal pads and accommodations, anterior orthotic edge lengthening, and extrinsic forefoot posting. If you’re still awake and reading this, WELL DONE!

SO, what if this doesn’t work? Primary surgical repair is an option, along with tendon transfer. Sometimes a judicial cortisone injection in the extra-articular space can help a lot too.

References

1. Yu GV, Judge MS, Hudson JR, Seidelmann FE. Predislocation Syndrome. JAPMA. 2002;92;182-199.

2. Keir R, Abrahamian H, Caminear D, et al. MR Arthrography of the Second and Third Metatarsophalangeal Joints for the Detection of Tears of Plantar Plate and Joint Capsule. AJR. 2010;194;1079-1081.

What is Acquired Adult Flat Foot?... How to help your patients avoid catastrophic foot surgery.