INTERPHALANGEAL ARTHRITIS (FOOT)
Hallux IPJ and Lesser Toe IPJ | Post-Traumatic and Degenerative
ANATOMICAL CLASSIFICATION
Critical Must-Knows
- Post-traumatic arthritis is the most common cause - previous fracture, dislocation, or turf toe injury
- Hallux IPJ arthritis more symptomatic than lesser toes - essential for push-off in gait
- Arthrodesis (fusion) is gold standard - eliminates pain, stable construct, minimal functional loss
- Fusion position critical: hallux IPJ fused in 10-15° plantar flexion to clear ground during gait
- Inflammatory arthritis (RA, psoriatic) can affect multiple IPJs simultaneously
Examiner's Pearls
- "Hallux IPJ fusion position: 10-15° plantar flexion, slight valgus (matches contralateral)
- "Lesser toe PIPJ: arthroplasty (resection) acceptable as motion less critical
- "K-wire fixation sufficient for lesser toes, plate/screw preferred for hallux IPJ
- "Non-union rare with rigid fixation and proper preparation (under 5%)
Clinical Imaging
Imaging Gallery
Critical IPJ Arthritis Concepts
Hallux IPJ vs Lesser Toes
Hallux IPJ arthritis is more significant than lesser toe IPJ arthritis. The hallux IPJ contributes to push-off power in gait. Lesser toe IPJs have minimal functional role. Symptomatic hallux IPJ requires surgical treatment; lesser toe IPJ can often be managed conservatively.
Post-Traumatic Etiology
Post-traumatic arthritis is the primary cause in younger patients. Previous fracture (especially intra-articular), dislocation, or severe turf toe injury damages articular cartilage. Degenerative arthritis predominates in older patients.
Arthrodesis Gold Standard
Fusion (arthrodesis) is the gold standard for symptomatic IPJ arthritis. Eliminates pain reliably, stable construct, minimal functional deficit (IPJs have limited motion normally). Arthroplasty reserved for lesser toes.
Fusion Position
Position is critical for hallux IPJ fusion: 10-15° plantar flexion, slight valgus to match contralateral. Excessive dorsiflexion causes nail to catch on ground. Excessive plantar flexion causes dorsal nail pressure in shoes.
At a Glance
Interphalangeal joint arthritis of the foot most commonly affects the hallux IPJ, which is functionally more significant than lesser toe IPJs due to its contribution to push-off power during gait. Post-traumatic arthritis (previous fracture, dislocation, turf toe injury) is the primary etiology in younger patients, while degenerative and inflammatory causes predominate in older populations. Arthrodesis (fusion) is the gold standard treatment for symptomatic hallux IPJ arthritis, achieving 90% union rates with rigid fixation and providing reliable pain relief with minimal functional deficit given the normally limited IPJ motion. The critical fusion position is 10-15° plantar flexion with slight valgus matching the contralateral toe—excessive dorsiflexion causes the nail to catch on the ground, while excessive plantar flexion creates dorsal nail pressure in footwear. Lesser toe IPJs can be managed with resection arthroplasty as motion is less critical; K-wire fixation suffices for lesser toes while plate/screw fixation is preferred for the hallux.
TRAUMACauses of IPJ Arthritis
Memory Hook:TRAUMA is the most common cause of IPJ arthritis in young patients!
PLANTHallux IPJ Fusion Position
Memory Hook:PLANT the hallux IPJ in slight plantar flexion!
PINSSurgical Approach Complications
Memory Hook:Watch for PINS complications after IPJ arthrodesis!
Overview and Epidemiology
Why IPJ Arthritis Matters
Interphalangeal joint arthritis in the foot is less common than MTP arthritis, but when symptomatic (especially hallux IPJ), it significantly impacts gait and footwear. The hallux IPJ is essential for push-off power. Unlike finger IPJs (where motion is critical), toe IPJs have minimal normal motion, making arthrodesis an excellent treatment with minimal functional loss. Post-traumatic arthritis from previous fracture or dislocation is the most common cause in younger patients, while degenerative arthritis predominates in older adults.
Epidemiology
- Prevalence: Less common than MTP arthritis (10-15% of forefoot arthritis)
- Age: Post-traumatic (20-50y), degenerative (over 50y)
- Gender: Male = female (post-traumatic), female predominance (degenerative)
- Location: Hallux IPJ greater than 80%, lesser toe PIPJ less than 20%
- Bilateral: Uncommon (unless inflammatory arthritis)
Risk Factors
Post-Traumatic:
- Previous IPJ fracture (especially intra-articular)
- IPJ dislocation (reduces but cartilage damaged)
- Severe turf toe (hallux IPJ cartilage injury)
- Chronic mallet or hammer toe deformity
Degenerative:
- Age over 60 years
- Obesity (increased forefoot load)
- High-impact activities (running, jumping)
Inflammatory:
- Rheumatoid arthritis, psoriatic arthritis
- Affects multiple IPJs simultaneously
Anatomy and Pathophysiology
IPJ Anatomy
The interphalangeal joints in the foot are hinge joints with minimal normal motion compared to fingers. Hallux IPJ normally has 40-60° dorsiflexion and 0-10° plantar flexion. Lesser toe PIPJ and DIPJ have 30-50° flexion. The collateral ligaments provide medial-lateral stability. The plantar plate (at MTP, not IPJ) does not extend to IPJ level. Because normal IPJ motion is limited, fusion causes minimal functional deficit.
IPJ Anatomy by Location
| Joint | Normal Motion | Functional Role | Arthritis Impact |
|---|---|---|---|
| Hallux IPJ | 40-60° dorsiflexion, 0-10° plantar flexion | Push-off power in gait, significant | High impact - pain with walking, shoe pressure |
| Lesser toe PIPJ | 30-50° flexion | Minimal functional role | Low impact - mostly cosmetic and shoe fitting |
| Lesser toe DIPJ | 20-30° flexion | Negligible functional role | Rarely symptomatic |
Pathophysiological Progression
Post-traumatic: Intra-articular fracture, dislocation, or severe hyperextension injury (turf toe) damages articular cartilage. Even if anatomically reduced, cartilage is permanently injured.
Damaged cartilage undergoes progressive degeneration. Loss of normal proteoglycan and collagen structure. Chondrocytes apoptosis. Subchondral bone exposed in areas.
Complete loss of cartilage. Exposed subchondral bone creates mechanical pain with motion and weight-bearing. Osteophyte formation at joint margins. Joint space narrowing on X-ray.
Joint collapse may occur. Chronic pain leads to altered gait (antalgic). Dorsal osteophytes cause shoe pressure. Surgical intervention required for symptom relief.
Post-Traumatic Arthritis
Mechanism:
- Intra-articular fracture (even if well-reduced)
- IPJ dislocation (cartilage shear injury)
- Severe turf toe (hallux IPJ cartilage contusion)
- Repeated microtrauma (athletics)
Timeline:
- Symptoms develop 6 months to 5 years post-injury
- Earlier onset with more severe initial injury
- X-ray changes may precede symptoms
Clinical Features:
- History of specific injury
- Younger patients (20-50 years)
- Unilateral involvement
- Progressive pain and stiffness
Post-traumatic is most common cause under age 50.
Clinical Presentation and Examination
History
- Pain location: Specific IPJ (hallux or lesser toe)
- Onset: Post-traumatic (months to years after injury), degenerative (insidious)
- Aggravating factors: Walking, push-off (hallux IPJ), shoe pressure
- Stiffness: Morning stiffness (inflammatory), end-of-day stiffness (degenerative)
- Previous treatment: Often tried NSAIDs, shoe modifications
- Functional impact: Difficulty with walking distance, athletic activities
Physical Examination
- Inspection: Swelling, osteophytes (dorsal prominence), malalignment
- Palpation: Tenderness over affected IPJ, warmth if inflamed
- ROM: Reduced ROM, pain at end-range, crepitus with motion
- Deformity: Hallux IPJ hyperextension or flexion contracture, hammer/mallet toe (lesser)
- Gait: Antalgic gait, reduced push-off (hallux IPJ arthritis)
- Footwear: Assess shoe wear pattern, pressure areas
Hallux IPJ Examination
For hallux IPJ arthritis, perform:
- ROM assessment: Compare to contralateral (normally 40-60° dorsiflexion)
- Grind test: Axially load and rotate IPJ - crepitus and pain suggests arthritis
- Dorsal osteophyte: Palpate dorsal joint - prominence indicates advanced disease
- Push-off test: Ask patient to perform single-leg toe raise - weakness/avoidance if painful
These findings confirm symptomatic arthritis requiring treatment.
Differential Diagnosis
Conditions Mimicking IPJ Arthritis
| Condition | Key Distinguishing Features | Diagnostic Test |
|---|---|---|
| IPJ gout | Acute onset, severe pain, erythema, asymmetric | Serum uric acid, joint aspiration (urate crystals) |
| IPJ infection (septic) | Acute, fever, systemic illness, recent trauma/surgery | Joint aspiration (cell count, culture) |
| Turf toe (acute) | Acute hyperextension injury, plantar plate tear | MRI (plantar plate injury, no chronic arthritis) |
| Nail bed pathology | Pain at nail, paronychia, ingrown nail | Inspection of nail and nail bed |
Investigations
Plain X-ray Assessment
Standard Views:
- AP foot: Shows IPJ alignment and joint space
- Lateral foot: Shows osteophytes, dorsal prominence
- Oblique foot: Additional detail of IPJs
Radiographic Findings:
- Joint space narrowing (bone-on-bone in severe cases)
- Osteophyte formation (especially dorsal)
- Subchondral sclerosis
- Subchondral cysts
- Malalignment (flexion or extension deformity)
Severity Grading:
- Mild: Joint space narrowing, small osteophytes
- Moderate: Significant narrowing, larger osteophytes, sclerosis
- Severe: Bone-on-bone contact, collapse, deformity
X-rays sufficient for diagnosis in most cases.
Management Algorithm
Imaging
Treatment Goal
The goal is pain relief and restoration of function. For symptomatic hallux IPJ arthritis, arthrodesis (fusion) is the gold standard - reliably eliminates pain with minimal functional deficit. Conservative treatment is first-line for mild symptoms. Lesser toe IPJ arthritis can often be managed conservatively or with arthroplasty (resection) if surgery needed.
Non-Operative Management
Indicated for:
- Mild to moderate symptoms
- Patient medically unfit for surgery
- Patient refuses surgery
Interventions:
Footwear Modification:
- Stiff-soled shoes (reduces IPJ motion)
- Rocker-bottom sole (offloads forefoot, reduces push-off stress)
- Extra depth toe box (accommodates dorsal osteophytes)
Orthotics:
- Carbon fiber plate insole (stiffens forefoot)
- Morton extension (limits hallux motion)
Medications:
- NSAIDs for pain and inflammation
- Intra-articular corticosteroid injection (temporary relief 3-6 months)
Activity Modification:
- Avoid high-impact activities
- Low-impact exercise (swimming, cycling)
Outcomes:
- 40-50% achieve acceptable symptom control
- Most eventually progress to surgery
Conservative treatment is palliative, not curative.
Complications
| Complication | Incidence | Risk Factors | Prevention/Management |
|---|---|---|---|
| Nonunion | Under 5% | Inadequate fixation, smoking, poor bone quality | Rigid fixation, smoking cessation, revision fusion if symptomatic |
| Malunion | 5-10% | Incorrect positioning during surgery | Careful positioning (10-15° plantar flexion hallux), check alignment intra-op |
| Pin tract infection | 5-10% | K-wire fixation | Pin care, early removal at 3-4 weeks, antibiotics if infected |
| Transfer metatarsalgia | Rare | Altered gait mechanics post-fusion | Proper fusion position, orthotics if symptomatic |
| Nail problems | 5% | Excessive plantar or dorsiflexion fusion | Correct positioning, may need nail removal |
| Neurovascular injury | Under 2% | Iatrogenic during exposure | Careful dissection, protect digital nerves |
Malunion Position Problems
Incorrect fusion position causes functional problems:
- Excessive dorsiflexion: Nail catches on ground during gait, painful
- Excessive plantar flexion: Dorsal toe pressure in shoes, nail driven dorsally
- Varus or valgus: Medial or lateral shoe pressure, unstable gait
Careful positioning and intra-operative verification essential.
Outcomes and Prognosis
Favorable Factors
- Rigid fixation (plate preferred over K-wires)
- Good bone quality
- Non-smoker
- Normal body weight
- Compliant with post-op protocol
- Correct fusion position
Unfavorable Factors
- Smoking (impairs bone healing)
- Poor bone quality (osteoporosis, RA)
- Inadequate fixation
- Infection
- Non-compliance with weight-bearing restrictions
- Inflammatory arthritis (higher nonunion risk)
Functional Outcomes
Hallux IPJ Fusion:
- Pain relief: 85-90% satisfied
- Union rate: 90-95% with rigid fixation
- Return to shoes: Most patients at 3-4 months
- Minimal functional deficit: IPJ has limited normal motion
Lesser Toe IPJ Surgery:
- Similar union rates with fusion
- Arthroplasty (resection): Less predictable but acceptable
- Cosmetic improvement with correction of hammer/mallet toe
Evidence Base and Key Studies
Hallux IPJ Arthrodesis Outcomes
- Union rate 94% with screw or plate fixation
- 85% patient satisfaction with pain relief
- Average time to union: 10 weeks
- Minimal functional deficit reported
Fusion Position and Functional Outcomes
- Optimal fusion position: 10-15° plantar flexion
- Excessive dorsiflexion causes nail ground strike
- Excessive plantar flexion causes shoe pressure
- Matching contralateral side improves satisfaction
Post-Traumatic Arthritis Development
- Intra-articular fractures develop arthritis in 30-50%
- Timeline: 6 months to 5 years post-injury
- Arthritis severity correlates with initial injury severity
- Anatomic reduction does not guarantee prevention
Inflammatory Arthritis IPJ Involvement
- RA affects foot IPJs in 15-20% of patients
- Usually multiple IPJs bilaterally
- Medical management (DMARDs) reduces surgical need
- Fusion outcomes similar to osteoarthritis if surgery needed
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Post-Traumatic Hallux IPJ Arthritis
"A 35-year-old footballer presents with 2 years of progressive hallux IPJ pain. He sustained a severe turf toe injury 3 years ago. Examination shows reduced hallux IPJ ROM (20° vs normal 60°), crepitus with motion, and tenderness. X-rays demonstrate joint space narrowing, osteophytes, and subchondral sclerosis. What is your diagnosis and management?"
Scenario 2: Inflammatory Arthritis Multiple IPJs
"A 48-year-old female with known rheumatoid arthritis presents with bilateral painful hallux and second toe IPJ swelling and stiffness. She has tried DMARDs and biologics with partial control. X-rays show erosive changes at multiple IPJs bilaterally. She requests surgical treatment for pain relief. How do you approach this?"
Scenario 3: Malunion After Hallux IPJ Fusion
"A 52-year-old male presents 6 months after hallux IPJ fusion performed elsewhere. The fusion has healed (solid union on X-ray) but he complains that his great toe nail catches on the ground when walking and is painful. X-rays show the IPJ fused in 30° dorsiflexion. What is the problem and how do you manage it?"
MCQ Practice Points
Most Common Cause
Q: What is the most common cause of hallux IPJ arthritis in patients under 50 years? A: Post-traumatic arthritis - previous intra-articular fracture, IPJ dislocation, or severe turf toe injury causing articular cartilage damage.
Gold Standard Treatment
Q: What is the gold standard surgical treatment for symptomatic hallux IPJ arthritis? A: Arthrodesis (fusion) - reliably eliminates pain, high union rate (90-95%), minimal functional deficit as IPJ has limited normal motion.
Fusion Position
Q: What is the correct position for hallux IPJ arthrodesis? A: 10-15° plantar flexion, slight valgus to match contralateral great toe, neutral rotation. Excessive dorsiflexion causes nail ground strike; excessive plantar flexion causes shoe pressure.
Fixation Method
Q: What fixation method is preferred for hallux IPJ arthrodesis? A: Plate and screw or lag screw - provides rigid fixation with highest union rate. K-wires acceptable for lesser toe IPJs but plate preferred for hallux.
Australian Context
Surgical Management: IPJ fusion for symptomatic arthritis is performed as day surgery in both public and private settings. Orthopaedic foot and ankle surgeons perform these procedures across metropolitan and regional centres.
Conservative Care: PBS-subsidised medications include simple analgesics and NSAIDs. Custom orthotics and accommodative footwear available through podiatry services with health fund rebates.
Smoking Cessation: Given the impact of smoking on fusion rates, patients should be referred to smoking cessation programs. Quitline and PBS-subsidised nicotine replacement therapy available.
Postoperative Rehabilitation: Weight bearing in stiff-soled shoe typically allowed immediately. Physiotherapy for gait retraining available through Medicare EPC referrals.
INTERPHALANGEAL ARTHRITIS (FOOT)
High-Yield Exam Summary
DEFINITION
- •IPJ arthritis: hallux IPJ, lesser toe PIPJ/DIPJ
- •Hallux IPJ most symptomatic (essential for push-off)
- •Post-traumatic (under 50y) vs degenerative (over 60y)
- •Inflammatory arthritis: bilateral, multiple IPJs
- •Limited normal IPJ motion = fusion causes minimal deficit
CAUSES
- •Post-traumatic: fracture, dislocation, turf toe
- •Degenerative: age-related (over 60y)
- •Inflammatory: RA, psoriatic (bilateral)
- •Timeline: symptoms 6mo-5y post-injury
CLINICAL FEATURES
- •Pain at specific IPJ with walking
- •Reduced ROM, crepitus with motion
- •Dorsal osteophytes (palpable prominence)
- •X-ray: joint space narrowing, osteophytes, sclerosis
CONSERVATIVE TREATMENT
- •Stiff-soled shoes or rocker-bottom
- •Carbon fiber plate insole
- •NSAIDs, intra-articular steroid
- •40-50% achieve symptom control
HALLUX IPJ FUSION
- •Gold standard for failed conservative
- •Position: 10-15° plantar flexion, slight valgus
- •Fixation: plate/screw (preferred) or lag screw
- •Union rate: 90-95% (rigid fixation)
- •Time to union: 8-12 weeks
KEY POINTS
- •Hallux IPJ more significant than lesser toes
- •Fusion eliminates pain, minimal functional loss
- •Correct position critical (10-15° plantar flexion)
- •RA: higher nonunion risk (5-10% vs under 5%)
- •Malunion causes nail or shoe pressure problems