Recurrent Patellar Dislocation

Definition and Epidemiology

• Campbell's Operative Orthopaedics 15th Ed 2026 (Ch. 52)
• Miller's Review of Orthopaedics 9th Edition

Pathomechanics

Risk Factors for Recurrence

• Campbell's Operative Orthopaedics 15th Ed 2026

Trochlear Dysplasia - Dejour Classification

• Type A: Shallow trochlea (sulcus angle > 145°)
• Type B: Flat or convex trochlea + supratrochlear spur
• Type C: Asymmetric - lateral convexity + medial hypoplasia + double contour sign
• Type D: Combines B + C features (cliff pattern)

Clinical Assessment

• Twisting mechanism or planted-foot rotation
• Audible/palpable "pop" followed by giving way - often confused with ACL injury in young patients
• Spontaneous reduction with knee extension is common
• Ongoing anterior knee pain ± instability

• Diffuse peripatellar swelling and tenderness (worse medially - MPFL injury)
• Positive patellar apprehension test (lateral translation at 0-30° flexion)
• J-sign: patella tracks laterally in full extension and reduces abruptly as flexion begins
• Lateral patellar glide > 3 quadrants (incompetent MPFL)
• Assess Q angle (> 20° abnormal), foot progression angle, femoral anteversion
• Quadriceps atrophy (thigh circumference)
• Examine for systemic hypermobility (Beighton score)

Imaging

• Lateral view: crossing sign, trochlear bump (supratrochlear spur), patella alta assessment
• Merchant/axial view: sulcus angle (normal ~137°), congruence angle (normal −8°), lateral patellar tilt
• Patellar height indices: Insall-Salvati ratio (>1.2 = alta), Caton-Deschamps index (>1.2 = alta)

• Gold standard for TT-TG distance (tibial tubercle to trochlear groove distance)
  • Normal: 9-13 mm
  • 15-20 mm: borderline

  • 20 mm: clearly abnormal, associated with instability

• Measures rotational deformities (femoral anteversion, tibial torsion)

• Best for MPFL integrity (usually torn at patellar insertion)
• Characteristic "kissing contusion": lateral femoral condyle + medial patella bruising
• Articular cartilage damage assessment
• Can estimate TT-TG (but tends to underestimate vs. CT)

Management

Non-operative (First-line for first-time dislocation)

• Short immobilization (1-3 weeks), then patellar stabilizing brace
• Physiotherapy: VMO strengthening, hip abductor and core strengthening, proprioception training
• Activity modification; weight loss if applicable
• Return to sport: 6-12 weeks when functional milestones are met
• In patients with hypermobile joints, conservative management is the mainstay - surgery outcomes are poor in this group

Indications for Surgery

• Associated osteochondral fracture (loose body)

• Recurrent instability (multiple events)
• First-time dislocation in high-risk anatomy (trochlear dysplasia + patella alta + young age)
• Contralateral recurrent instability

Surgical Treatment

Treatment Table (Campbell's)

Key Procedures

1. MPFL Reconstruction (Workhorse procedure - "Low risk, high reward")

• Primary procedure for recurrent MPFL deficiency ± trochlear dysplasia
• Graft: gracilis or semitendinosus autograft (or allograft)
• Femoral attachment at the Schottle point (1 mm anterior to posterior cortex line, 2.5 mm distal to posterior medial femoral condyle, proximal to Blumensaat line)
• Tunnel placement errors:
  • Too proximal = tight in flexion
  • Too distal = loose in flexion
• Key complication: medial patellar instability or medial facet OA from overtightening

2. Tibial Tubercle Anteromedialization (Fulkerson / Elmslie-Trillat)

• Indicated when TT-TG > 20 mm (or > 15 mm with trochlear dysplasia)
• Elmslie-Trillat: pure medialization - quicker healing, lower fracture risk
• Fulkerson: oblique osteotomy providing anteromedialization (30° = 1 mm anterior per 2 mm medial; 45° = 1:1 ratio)
  • Best for lateral/distal facet chondral damage
  • Contraindicated for proximal/medial facet arthritis
• Often combined with MPFL reconstruction

3. Trochleoplasty ("High risk, high reward")

• Indicated for severe trochlear dysplasia (convex/flat trochlea) unresponsive to other procedures
• Low recurrence rate but significant risk: osteonecrosis, arthrofibrosis, progressive DJD of lateral facet

4. 3-in-1 Procedure (Oliva) - for open physes / skeletally immature

• Lateral release + VMO advancement + transfer of medial third of patellar tendon to MCL
• Used when tibial tubercle transfer is unsafe (open physes)
• Steps: lateral retinacular release → mobilization of VMO insertion → medial 1/3 patellar tendon detached distally, transferred medially and fixed with suture anchors at 45° → VMO advanced 10 mm distally

5. Lateral Release - indicated ONLY for excessive lateral pressure syndrome

• Not indicated as isolated treatment for patellar instability
• May actually increase risk of both medial and lateral subluxation if used in isolation

Special Considerations

Pediatric / Open Physes

• Tibial tubercle osteotomy is contraindicated (physeal injury risk)
• MPFL reconstruction must avoid the physis
• 3-in-1 soft-tissue procedure or MQTFL (medial quadriceps tendon-femoral ligament) reconstruction preferred
• Epiphysiodesis for angular deformities

Hypermobility Syndromes

• Patellar instability in hypermobile joints is primarily managed conservatively
• Joint hypermobility is a poor prognostic indicator for operative outcomes
• Surgery should not be the mainstay of treatment in this group

"Miserable Malalignment Syndrome"

• Combination of femoral anteversion + genu valgum + external tibial torsion + pronated feet
• Exacerbates patellar instability in adolescents
• May require rotational osteotomy in severe cases

Complications of Recurrent Dislocation

• Articular cartilage damage (medial patellar facet - most common site)
• Osteochondral fractures and loose bodies
• Progressive patellofemoral osteoarthritis
• Ongoing anterior knee pain
• Quadriceps inhibition and muscle atrophy

Recent Evidence (2024-2026)

Congenital Talipes Equinovarus (CTEV / Clubfoot)

Definition

Epidemiology

• Incidence: ~1 in 1,000 live births
• Boys affected twice as often as girls
• 50% of cases are bilateral
• Most common serious congenital foot anomaly

Pathoanatomy

• Medial rotation of the calcaneus under the talus
• Medial displacement of the navicular (onto the medial aspect of the talar head)
• Medial displacement of the cuboid
• Shortening/contracture of: Achilles tendon, tibialis posterior, FHL, FDL, intrinsic muscles, joint capsules, ligaments, and plantar fascia

Etiology

Syndromic and neurogenic clubfeet are more rigid, have higher recurrence rates, and respond less well to conservative management than idiopathic forms.

Clinical Assessment

History

• Visible foot deformity at birth
• Family history (genetic predisposition)
• Prenatal diagnosis often possible on USS (~ 20 weeks)

Examination

• Rigid vs. positional (postural) clubfoot - distinguish by gentle manipulation
• Check for associated spine (MMC), hip dysplasia
• Assess skin creases: deep medial and posterior creases indicate severity
• In older/untreated: weight-bearing on dorsolateral foot, callosities, short leg, calf atrophy

Severity Scoring

Pirani Score (0-6, most widely used)

1. Curved lateral border
2. Medial crease
3. Lateral talar head coverage

Dimeglio Classification (0-20)

• Grade I (Benign): 0-5 pts
• Grade II (Moderate): 6-10 pts
• Grade III (Severe): 11-15 pts
• Grade IV (Very Severe): 16-20 pts

Radiographic Features

• AP view (Kite angle - talocalcaneal angle): Normal 20-40°; reduced (<20°) in CTEV due to parallelism of talus and calcaneus
• Lateral/Turco view (dorsiflexion lateral): Talocalcaneal angle < 35° (normal)
• Talus-1st metatarsal angle (AP): Negative in CTEV (normally 0-20°)
• Key radiographic sign: "Parallelism" - talus and calcaneus axes run parallel rather than diverging

Treatment

1. Ponseti Method (Gold Standard - First-line)

• Serial weekly gentle manipulation and long-leg plaster casting
• Corrects deformities in the CAVE sequence
• Uses the lateral talar head as a fulcrum for adduction/varus correction
• Supinates forefoot (do NOT pronate - creates rocker-bottom)

• Total: typically 5-6 casts required
• Final cast placed in 70° of abduction
• >90% success in children under 2 years, even after previous unsuccessful treatment

• Required in ~90% of patients to fully correct equinus
• Done under local anesthesia (office/clinic) before final cast application
• Prevents rocker-bottom deformity (do not dorsiflex through midfoot before varus corrected)
• Cast then worn for 3 more weeks post-tenotomy

• Mandatory - most important factor in preventing recurrence
• Full-time for 3 months, then during sleep and naps for 3-4 years
• Brace: shoes set at 60-70° abduction bilaterally (40° for unilateral)
• Recurrence is most strongly associated with brace non-compliance

• Accelerated biweekly casting (faster correction)
• Fiberglass casting = plaster results
• Bracing to age 4 may be superior to stopping at age 3

2. Anterior Tibial Tendon Transfer (ATTT)

• Indicated for dynamic supination deformity (residual or recurrent varus driven by anterior tibialis over-activity)
• Transfer of the anterior tibial tendon from its lateral cuneiform insertion to the middle/lateral cuneiform or cuboid
• Usually combined with recasting
• Typically performed at age 2.5-4 years (when child begins walking consistently)

3. Operative Treatment

Posteromedial Release (PMR) - Turco / Cincinnati approach

• Tendon lengthening (Achilles, tibialis posterior, FHL, FDL) + capsulotomy (subtalar, tibiotalar, talonavicular joints) + realignment
• Posterior tibial artery must be carefully protected (anterior tibial artery often absent)
• Typically performed at 6-12 months
• Now largely replaced by Ponseti method; reserved for true failures

For Older Children (3-10 years) with Residual Deformity:

• Medial opening-wedge osteotomy or lateral column shortening (cuboid decancellation/cuneiform osteotomy) - for residual adductus
• Calcaneal osteotomy - for residual varus/valgus

For Late-Presenting / Severe Neglected Clubfoot:

• Triple arthrodesis (subtalar + talonavicular + calcaneocuboid) - for children presenting late (adolescence/adults)
  • Contraindicated in insensate feet (risk of ulceration from rigidity)
• Talectomy - salvage for severely deformed rigid clubfoot in older child
  • Complete talus removal required (any remnant regrows and causes recurrence)
  • Achilles tendon may also need resection after talectomy
• Ilizarov frame - for complex recurrent/neglected deformities

Complications

Special Populations

Myelomeningocele-associated Clubfoot

• 30-50% of MMC children affected; deformity is more rigid, resembles arthrogryposis
• Ponseti method still first-line but: 68% early relapse, 33% require surgical release, 10% no improvement
• Surgery: radical posteromedial-lateral release via Cincinnati incision at 10-12 months
• Active anterior tibial tendon should be tenotomized to prevent recurrent supination
• Insensate feet are a contraindication to triple arthrodesis

Arthrogryposis

• Very rigid; requires more aggressive casting and higher surgical rates

Recent Evidence (2024-2026)

• A 2024 network meta-analysis (PMID 38015923) in JBJS confirmed Ponseti casting as the optimal treatment for idiopathic clubfoot across outcomes compared to other methods.
• A 2026 systematic review (PMID 40888800) found fiberglass and plaster casts produce equivalent outcomes in the Ponseti method, supporting use of either material.
• A 2024 systematic review (PMID 39365806) confirmed Ponseti method is effective even in myelodysplastic clubfeet, though with higher recurrence.

ACL Reconstruction

Background

• Restore normal knee kinematics (anterior translation + rotation)
• Return patient to full activity
• Prevent secondary meniscal/chondral injury and progressive arthrosis

Indications for Reconstruction

• Young, active patients wishing to return to pivoting/cutting sports
• Acute ACL tear with concomitant repairable meniscal tear
• Chronic ACL insufficiency with functional instability
• First-time dislocation with osteochondral fracture (relative)
• Pediatric patients (special considerations apply - physeal-sparing techniques)

Graft Selection

Biomechanical Strength Comparison (Ultimate Load to Failure)

• Campbell's Operative Orthopaedics 15th Ed 2026, Table 56.2

1. Bone-Patellar Tendon-Bone (BPTB) Autograft

• Bone-to-bone healing (fastest incorporation - ~6 weeks)
• High strength and stiffness
• Lower retear rate in young athletes
• More likely to achieve: normal Lachman, normal pivot shift, KT-1000 side-to-side difference < 3 mm

• Anterior knee pain (kneeling pain - "kneeler's pain")
• Patellar tendinitis
• Patellar fracture risk (especially if graft too deep)
• Greater risk of extension loss
• Higher patellofemoral pain
• Some studies show higher arthritis risk at 5-7 years vs. hamstring

2. Four-Strand Hamstring (Semitendinosus ± Gracilis) Autograft

• Highest biomechanical strength (quadrupled)
• Less anterior knee pain/kneeling pain
• Less extension loss
• Lower patellofemoral crepitance

• Graft creep/relaxation over time (more than ligamentous grafts)
• Slower soft-tissue tunnel incorporation (2-3 weeks longer than bone plug)
• Hamstring weakness (~20% loss of knee flexion/internal rotation strength)
• Saphenous nerve branch injury risk
• Must be ≥ 8 mm diameter - smaller grafts have significantly higher revision rates (0.82× lower revision risk per 0.5 mm increase from 7-9 mm)

3. Quadriceps Tendon Autograft

• Growing in popularity, especially with bone plug from patella
• Strength intermediate between BPTB and hamstring
• Avoids anterior knee pain of BPTB while providing bone-to-bone fixation option
• Patellar fracture risk similar to BPTB

4. Allograft

• Failure rates 2-5 times higher than autograft in young/active patients
• Slower incorporation into bone tunnels
• Not recommended in young patients (age < 34 years)
• Acceptable in older/lower-demand patients (no difference in retear > age 34)
• Infection risk: Clostridium, hepatitis, HIV (1:1.5-6 million)
• Chemically processed/irradiated allografts have higher failure rates than fresh-frozen

Surgical Technique

Tunnel Placement - The Critical Variable

• Anatomic reconstruction targets the center of the femoral ACL footprint (10- or 2-o'clock position, or "low and deep" on the posterior condyle)
• Achieved via independent femoral drilling (outside-in or accessory medial portal) rather than transtibial technique
• More horizontal graft position reduces rotational instability
• Single-bundle vs. double-bundle: currently no difference in patient-reported outcomes

• Aim: center of the tibial ACL footprint (lateral to PCL, anterior to posterior horn of lateral meniscus)
• Angle: typically 55-65° to the tibial plateau

Fixation Methods

• Bone-to-bone (BPTB): Interference screws - provide excellent fixation if properly placed
• Soft-tissue grafts (hamstring): Interference screws (BioScrew) + tunnel compaction + secondary fixation (cortical buttons, cross-pins)
• Bone plug incorporation: ~6 weeks; soft-tissue graft incorporation: 8-12 weeks
• Tunnel widening: aperture widening occurs up to 6 weeks, then narrows by 12 weeks

Anterolateral Ligament (ALL) Reconstruction - Augmentation

• Indicated for high-risk patients: 3+ pivot shift, hyperextension > 5°, high-demand athletes
• ACL + ALL reconstruction reduces failure rate to < 3%, which is:
  • 2.5× lower than isolated BPTB
  • 3.1× lower than isolated hamstring reconstruction
• Medial meniscal repair failure also 2× lower with combined reconstruction
• Technique: gracilis autograft fixed 8 mm proximal and 4.3 mm posterior to lateral epicondyle (femur), and 22 mm posterior to Gerdy's tubercle (tibia)

Physeal-Sparing Techniques (Pediatric)

• All-epiphyseal or combined physeal-sparing techniques to avoid growth disturbance
• Soft-tissue fixation preferred over bone plugs crossing physis
• MQTFL/MPFL-type reconstruction approaches used in some cases

Complications

Tunnel Malposition (Most Common Technical Error)

Interference Screw Errors

• Femoral divergence > 30°: reduced pullout strength
• Tibial divergence > 15°: reduced pullout strength

Other Complications

Rehabilitation

Key Principles

Return to Sport Criteria

• Minimum 6 months after surgery (animal studies suggest 6-12 months for graft maturation)
• ≥ 80% quadriceps strength symmetry vs. contralateral limb
• Early return to high-level sport is a significant risk factor for ACL reconstruction failure
• Prehabilitation (pre-operative rehab) improves short- and long-term outcomes

Blood Flow Restriction (BFR) Training

• Air tourniquet proximally during therapy
• Low-intensity exercise with vascular occlusion promotes muscle hypertrophy
• Attenuates quadriceps atrophy post-operatively

Exercise Guidance

• Avoid: Open kinetic chain (OKC) extension in last degrees of extension, especially in first 6 weeks
• Prefer: Closed kinetic chain (CKC) exercises (squats, leg press, cycling)
• CPM machines: not routinely recommended (no proven benefit)
• No difference between accelerated and standard rehabilitation programs

Results

Revision ACL Reconstruction

1. Technical: tunnel malposition (most common), vertical graft placement, poor fixation
2. Missed concomitant injuries: posterolateral corner, MCL, ALL
3. Alignment: varus alignment or excessive posterior tibial slope increases graft stress
4. Biological: poor graft incorporation
5. Patient factors: young age, early return to sport, hyperextension laxity > 5°

Recent Evidence (2023-2026)

• A 2025 systematic review/meta-analysis (PMID 39836368) comparing BPTB vs. hamstring autograft found no significant difference in return to sport or graft failure rates, supporting equipoise in graft selection.
• A 2023 meta-analysis (PMID 36189967) identified young age, hamstring graft, and small graft diameter as risk factors for revision/rerupture.
• A 2025 systematic review (PMID 40276858) confirmed prehabilitation before ACL reconstruction is safe and provides short- and long-term benefits.