Plantar Plate Dysfunction

Anatomy

• Distally — firmly attached to the plantar base of the proximal phalanx
• Proximally — loosely attached to the metatarsal head (this proximal insertion is the weak point prone to tearing)
• Laterally — connected via the deep transverse metatarsal (intermetatarsal) ligament to adjacent plantar plates
• Dorsally — the margins attach to the accessory collateral ligaments and the extensor sling (transverse lamina of the extensor aponeurosis)
• Plantarly — attached to the flexor tendon sheath, plantar aponeurosis longitudinal septa, and plantar fascia

What Is Plantar Plate Dysfunction?

Aetiology & Risk Factors

• Long 2nd metatarsal (index minus / Greek foot) — increased load under 2nd MTP
• Hallux valgus — transfers load laterally to 2nd MTP
• Equinus / tight gastrocnemius — increased forefoot loading
• High-heeled or narrow footwear — sustained dorsiflexion position
• Repetitive microtrauma — runners, court sports players
• Iatrogenic — steroid injection into the MTP joint can attenuate the plantar plate, leading to crossover toe deformity
• Inflammatory arthropathy (RA, gout)

Clinical Presentation

• Pain localised to the plantar aspect of the lesser MTP joint, often described as walking on a "stone"
• Swelling at the MTP joint ("sausage toe" / synovitis)
• Plantar callosity under the affected metatarsal head
• Toe deviation — the toe may drift dorsally or medially (crossover toe) as the plate fails
• Worse with barefoot walking, pushing off, and high-heeled shoes
• Morning stiffness less pronounced than in inflammatory arthritis

Clinical Tests

1. Lachman / Anterior Drawer Test of the MTP Joint (most sensitive)

• Hold the metatarsal shaft stable with one hand
• Grasp the proximal phalanx of the affected toe between thumb and index finger
• Apply a dorsal thrust force (push the toe up/dorsally)
• Positive: pain elicited at the MTP joint, or excessive dorsal translation (>2 mm compared to the adjacent toes), or instability/subluxation

2. Paper Pull-Out Test (Kelikian Push-Up Test / Toe Purchase Test)

• A sheet of paper is placed under the toes on a flat surface
• The patient pushes all toes down against the paper
• The examiner attempts to pull the paper out from under the affected toe
• Positive: paper slides out easily, indicating loss of flexor purchase due to plantar plate failure

3. Digital Compression / Squeeze Test

• Compress the MTP joint from dorsal to plantar
• Positive: localised plantar tenderness under the metatarsal head

4. Varus/Valgus Stress Testing

• With the MTP joint in neutral, apply medial and lateral stress
• Assesses collateral ligament integrity alongside the plantar plate
• In crossover toe deformity, lateral collateral attenuation is typically found

5. Sagittal Plane Stability Assessment

• Observe the toe in stance and single-leg heel raise
• Note any dorsal float (toe no longer plantarflexing during propulsion)
• Reduction in toe purchase in heel raise = plantar plate incompetence

Investigations & Imaging

Management

Conservative (First-Line — UK Podiatry-Led)

Important UK Practice Point: Corticosteroid injection into the MTP joint is contraindicated in suspected plantar plate injury — it can cause iatrogenic plantar plate attenuation and lead to or worsen crossover toe deformity.

Orthotic / Insole Prescription for Plantar Plate Dysfunction

Key Elements of the Prescription:

• Placed proximal to the metatarsal head(s) — typically at the proximal 1/3 of the metatarsal shaft
• Elevates the metatarsal shaft, decompresses the metatarsal head, and shifts load away from the symptomatic MTP joint
• Size and density adjusted to tolerance

• Silicone or felt toe prop under the proximal phalanx of the affected digit
• Maintains plantarflexion of the toe, restoring flexor purchase and preventing dorsal drift
• Essential in grade 2–3 dysfunction

• A cut-out or recess under the 2nd (or affected) metatarsal head can be added to a custom device to reduce direct pressure
• Kinetic wedge: 1st ray cut-out promotes 1st ray plantarflexion and may redistribute load if 2nd MTP is the primary problem

• If hallux valgus is a contributing driver of 2nd MTP overload, medial arch support and toe spacer are incorporated
• Reduces lateral transfer of propulsive load onto the 2nd MTP joint

• Modest heel raise (3–6 mm) reduces ankle equinus contribution to forefoot loading

• Custom polypropylene or carbon fibre orthosis with forefoot extension for severe cases
• A stiff forefoot extension (rocker modification) limits MTP dorsiflexion during propulsion — the primary injury mechanism
• Use a full-length orthosis with digital accommodations rather than a 3/4 device in symptomatic cases

• Rocker-sole shoe or metatarsal bar added to the shoe externally limits MTP extension during toe-off
• Considered when insole modifications alone are insufficient

Operative (When Conservative Fails, Typically >3–6 Months)

Summary for UK Podiatric Practice

1. Diagnose clinically using the anterior drawer test (most sensitive), toe purchase test, and varus/valgus stress testing
2. Image with ultrasound or MRI — MR arthrogram if grading is needed prior to surgical referral
3. Grade the injury using the Thompson & Hamilton system to guide management intensity
4. First-line: toe taping + metatarsal pad + footwear advice + intrinsic strengthening
5. Insole prescription: metatarsal dome proximal to the head + toe prop + rocker/stiff forefoot extension ± hallux valgus correction
6. Avoid corticosteroid injection into the MTP joint
7. Refer for surgical opinion after 3–6 months failed conservative care, or earlier in grade 3–4 tears with progressive deformity

Ankle Pressure Thresholds in Podiatry

How Ankle Pressure Is Measured

Clinical Significance of Ankle Pressure Thresholds

Ankle Pressure < 100 mmHg

• Indicates haemodynamically significant peripheral arterial disease (PAD)
• In a healthy limb, ankle systolic pressure should be equal to or slightly higher than brachial pressure (the leg is normally ~10–20 mmHg higher due to pulse pressure amplification)
• A value below 100 mmHg suggests arterial insufficiency is present and requires further vascular assessment
• Clinically: the patient may be asymptomatic or have mild-to-moderate claudication
• At this level, wound healing may already be compromised — sufficient for intact skin but not for tissue repair
• In UK podiatric practice, values below 100 mmHg prompt caution with any compressive therapy or sharp debridement

Ankle Pressure < 70 mmHg

• Indicates critical limb ischaemia (CLI) territory when ulceration or tissue loss is present
• Per Schwartz's Principles of Surgery: "For patients with ulcers or gangrene, the presence of CLI is suggested by an ankle pressure less than 70 mmHg or a toe systolic pressure less than 50 mmHg"
• At this level:
  • Healing of wounds is severely impaired — active tissue repair demands far more perfusion than intact skin maintenance
  • Any existing ulceration is unlikely to heal without vascular intervention
  • Urgent vascular surgical referral is indicated
  • Corresponds approximately to Fontaine Stage III–IV or Rutherford Category 4–5 (rest pain / minor tissue loss)
• UK podiatry implication: compression bandaging is absolutely contraindicated; no elective podiatric procedures; patient requires immediate onward referral via the vascular pathway

Ankle Pressure < 50 mmHg

• Indicates severe critical limb ischaemia with a high risk of limb loss
• Per Schwartz's: "Ischaemic rest pain most commonly occurs below an ankle pressure of 50 mmHg or a toe pressure less than 30 mmHg"
• At this level:
  • The patient will typically have ischaemic rest pain — pain at rest (especially nocturnal), often relieved by hanging the leg dependent
  • Existing tissue loss / gangrene is present or imminent
  • Limb salvage requires urgent revascularisation (angioplasty, bypass, or stenting)
  • Without intervention, major amputation is likely within weeks to months
  • Corresponds to Rutherford Category 4–6 / Fontaine Stage III–IV

Summary Table

Rutherford / Fontaine Classification (for context)

Important Caveats in UK Podiatric Practice

1. Calcified / non-compressible vessels — Ankle pressures can be falsely elevated in diabetes and renal failure due to medial calcinosis. An ankle pressure >200 mmHg or a non-compressible artery should prompt toe pressure or ABPI with toe brachial pressure index (TBPI) instead (toe pressure <30 mmHg = CLI; toe pressure <70 mmHg = impaired healing)
2. ABPI vs. absolute pressure — The ABPI ratio is more commonly used in UK vascular screening. An ABPI <0.5 roughly correlates with ankle pressures in the CLI range; ABPI <0.9 indicates PAD
3. Wound healing thresholds are higher than rest pain thresholds — tissue repair requires more perfusion than maintaining intact skin, which is why the wound healing threshold (~70 mmHg) is above the rest pain threshold (~50 mmHg)
4. Doppler waveform quality should be assessed alongside the pressure — a monophasic or absent waveform with a borderline pressure carries greater clinical concern than the same pressure with a biphasic waveform

Patient Advice: Ankle Pressure Below 100 mmHg (PAD)

Quick note on terminology: You said "API" — I'll assume you mean ankle systolic pressure below 100 mmHg, which indicates peripheral arterial disease (PAD). If you meant ABPI (Ankle-Brachial Pressure Index) below 1.0, the same advice applies — both indicate reduced arterial blood flow to the feet and legs.

1. Smoking Cessation — Most Important Single Action

• Stop smoking immediately — smoking is the single most damaging risk factor for PAD and directly causes the arteries to narrow further
• Smoking significantly increases the risk of PAD progressing to critical limb ischaemia, amputation, heart attack, and stroke
• Smoking cessation is associated with decreased mortality and improved amputation-free survival
• Refer to NHS Stop Smoking Services — nicotine replacement therapy, varenicline (Champix), or bupropion can all help
• Even cutting down helps, but complete cessation is the goal

2. Foot Care — Critical in Podiatry Practice

• Inspect both feet every day — look at the tops, soles, between the toes, and around the heels; use a mirror if needed or ask someone to help
• Report any new sores, blisters, cuts, colour changes, or wounds immediately — do not wait; even a small cut can become serious
• Never walk barefoot — always wear shoes or slippers, even indoors
• Avoid extremes of temperature — do not use hot water bottles, heated insoles, or sit too close to radiators (reduced sensation means burns can go unnoticed)
• Do not cut corns or hard skin yourself — see your podiatrist; home cutting risks unnoticed injury
• Moisturise dry skin daily (but not between the toes — moisture between toes encourages fungal infection)
• Cut toenails straight across — or have them cut by a podiatrist
• Check shoes and socks before putting them on for any objects, rough seams, or debris

3. Footwear Advice

• Wear well-fitting, supportive shoes with a wide toe box — avoid tight, narrow, or pointed shoes
• Avoid high heels — they increase forefoot pressure and reduce circulation
• Seam-free socks reduce friction; avoid tight elastic sock tops that constrict circulation
• Consider podiatric footwear assessment — if there are areas of high pressure, cushioned insoles or off-loading footwear can reduce ulceration risk

4. Exercise

• Supervised walking exercise is recommended — a structured programme of walking to the point of claudication pain, resting, then repeating
• Regular exercise improves collateral circulation, walking distance, and quality of life
• Aim for at least 30 minutes, 3 times per week, gradually increasing
• Refer to a supervised exercise programme (available on the NHS for PAD patients)
• Exercise has been shown to improve symptoms comparably to some interventional procedures in mild-to-moderate PAD

5. Cardiovascular Risk Factor Control

• Statins — all patients with PAD should be on a statin; it reduces cardiovascular events, slows PAD progression, and improves walking distance
• Antiplatelet therapy — aspirin (75 mg daily) or clopidogrel (75 mg daily) is recommended to reduce the risk of heart attack, stroke, and death; this is a GP/medical decision

6. Diet

• Heart-healthy diet: low saturated fat, low salt, low refined sugar, high in fruit, vegetables, and wholegrains (Mediterranean-style diet)
• Reduce processed food and red meat
• Stay well hydrated — dehydration thickens blood and worsens circulation

7. When to Seek Urgent Help

• A new ulcer, wound, or area of skin breakdown that does not heal within 2 weeks
• Sudden worsening of pain in the foot or leg, including pain at rest or at night (rest pain = worsening ischaemia)
• The foot becoming cold, white, blue, or numb suddenly (this is a vascular emergency — call 999)
• Increasing redness, swelling, or discharge from any foot wound (infection in an ischaemic foot is limb-threatening)

8. Monitoring & Follow-Up

• Regular podiatry review — frequency depends on risk level; at minimum annually, more often if wound care is needed
• Vascular review — GP should refer to vascular surgery if symptoms progress or ankle pressure falls further
• Do not ignore symptoms — PAD is a progressive condition, but risk factor control significantly slows progression

Summary Card for the Patient

Plantar Plate Dysfunction — Comprehensive Podiatry (UK) Reference

1. Anatomy Recap

• Deep transverse intermetatarsal ligament → links adjacent plantar plates
• Accessory collateral ligaments (metatarsoglenoid suspensory ligaments) → attach to medial/lateral borders
• Extensor sling (transverse lamina) → connects dorsally
• Flexor tendon sheath and plantar fascia → plantar attachments

2. Risk Factors

Intrinsic (Structural/Biomechanical)

Extrinsic (Footwear / Activity)

Iatrogenic

• Corticosteroid injection into the MTP joint — directly attenuates the plantar plate fibrocartilage; the most well-documented iatrogenic cause of crossover toe deformity

3. Pathophysiology

4. Assessment

Subjective History

• Location: plantar/plantar-lateral 2nd (most common) or 3rd MTP joint
• Character: aching, pressure-like, "walking on a stone" or "walking on a lump"
• Aggravating factors: barefoot walking, propulsion, heel raise, high heels
• Time course: insidious onset — often weeks to months before presentation
• Footwear history: high heels, narrow toe box
• Activity level: runners, court sports
• Previous injections into or around the MTP joint (iatrogenic risk)
• Associated deformity: progressive toe drift, crossing over hallux

Observation (Static and Dynamic)

5. Clinical Tests

Test 1: Anterior (Lachman) Drawer Test — Most Sensitive Test

• Stabilise the metatarsal shaft between thumb and index finger of one hand
• Grasp the proximal phalanx of the affected digit between thumb and index finger of the other hand
• Apply a sharp dorsal thrust — push the toe upwards/dorsally
• Positive: reproduction of the patient's plantar pain at the MTP joint, or excessive dorsal translation (>2 mm versus adjacent toes), or subluxation/dislocation
• Clinical note: a positive result in the absence of visible deformity is the classic presentation of MTP instability / early PPD

Test 2: Paper Pull-Out / Toe Purchase Test (Kelikian Test)

• Place a sheet of paper or thin card under all lesser toes with the patient standing
• Ask the patient to actively push the toes down and grip the paper
• Attempt to pull the paper from under the affected toe
• Positive: paper slides out easily under the affected digit — indicates loss of active flexor purchase (FDB/FDL) due to plate incompetence and dorsal subluxation

Test 3: Varus/Valgus Stress Test

• With the MTP joint held in neutral, apply a medial (varus) then lateral (valgus) stress to the proximal phalanx
• Assess for medial or lateral laxity compared with the adjacent toes
• Positive: excessive medial laxity (lateral collateral attenuation) in crossover toe; or lateral laxity (medial collateral) depending on deformity direction
• Grading: compare bilaterally

Test 4: Digital Compression Test

• Compress the MTP joint from dorsal to plantar using thumb and index finger
• Positive: localised plantar tenderness directly under the metatarsal head
• Useful for differentiating from interdigital neuroma (which has positive Mulder's click, tenderness in the interspace rather than under the metatarsal head)

Test 5: Single-Leg Heel Raise Assessment

• Ask the patient to perform a single-leg heel raise, observing the toe in the sagittal plane
• Positive: the affected digit fails to plantarflex and purchase the ground during the heel raise
• Indicates inability of the flexor complex to maintain sagittal plane stability — confirms functional plantar plate insufficiency
• Compare bilaterally

Test 6: Passive MTP Dorsiflexion Provocation

• With the ankle in neutral, passively dorsiflex the MTP joint to approximately 90°
• Apply downward pressure on the metatarsal head
• Positive: pain reproduced at the plantar MTP joint
• Simulates the loading pattern during toe-off that stresses the plantar plate

Differential Diagnosis to Exclude

6. Gait Deviations

7. Orthotic / Insole Management

1. Offload the plantar plate — reduce compressive and shear force at the MTP joint
2. Restore sagittal plane toe alignment — maintain the toe in plantarflexion
3. Reduce MTP dorsiflexion moment during propulsion
4. Address biomechanical drivers — equinus, hallux valgus, hypermobile 1st ray, etc.

Element 1: Metatarsal Dome / Metatarsal Pad

• Placement: proximal to the metatarsal head(s), at the proximal 1/3 of the metatarsal shaft — not under the metatarsal head
• Function: elevates the metatarsal shaft, depresses the metatarsal head relative to ground, redistributes load away from the symptomatic MTP joint
• Specification: 3–5 mm semi-compressed felt or PPT foam dome, teardrop shape; for a custom device, incorporate into the shell as a built-in raise
• Common error: placing the pad too distally (under or distal to the metatarsal head) — this increases loading, not reduces it

Element 2: Toe Prop / Digit Prop

• Placement: under the plantar aspect of the proximal phalanx of the affected digit
• Function: mechanically maintains the proximal phalanx in plantarflexion, restoring the flexor tendon's line of action and preventing dorsal subluxation
• Materials: medical grade silicone (custom moulded), or PPT/plastazote toe prop
• A combined loop-and-prop style silicone device can be prescribed — the proximal loop anchors over the digit, the distal pad sits under the proximal phalanx
• Essential in grade 2–3 dysfunction where passive plantarflexion is lost

Element 3: Forefoot Extension / Stiff Forefoot Platform

• A full-length orthotic shell (polypropylene or carbon fibre) with a rigid forefoot extension limits MTP dorsiflexion during terminal stance
• The stiff forefoot platform acts as a functional rocker — propulsion occurs over the rigid plate rather than through the MTP joints
• Rocker-sole modification to the shoe augments this effect; a forefoot rocker placed proximal to the MTP joints is the most effective shoe modification for offloading PPD

Element 4: Medial Arch Support / Rearfoot Posting

• If pes planus / overpronation is a driver:
  • Medial longitudinal arch support — semi-rigid or custom orthosis with a medial skive or medial flange
  • Rearfoot varus posting (3–5°) to control subtalar pronation and reduce medial column collapse
  • This indirectly reduces the duration and magnitude of the propulsive load on the 2nd MTP joint
• If hallux valgus is contributing: incorporate a 1st ray cutout (Morton's extension reversed) or medial toe spacer

Element 5: First Ray Cutout / Kinetic Wedge

• A 1st ray cutout beneath the 1st metatarsal head encourages 1st ray plantarflexion
• This promotes normal load sharing through the 1st MTP joint, reducing the lateral transfer of load that overloads the 2nd MTP
• Particularly useful when 1st ray hypermobility is the primary driver

Element 6: Heel Raise

• A 3–6 mm heel raise (bilateral to avoid leg length discrepancy) reduces gastrocnemius contribution to equinus and decreases forefoot dorsiflexory demand
• Indicated when ankle equinus is a contributing factor

Summary Orthotic Prescription Template

8. Conservative Management Summary

9. Classification — Thompson & Hamilton Grading (UK Standard)