PIGMENTED VILLONODULAR SYNOVITIS (PVNS)
Benign Proliferative Synovial Disorder | Locally Aggressive | High Recurrence Risk
PVNS Classification
Critical Must-Knows
- PVNS is now classified as tenosynovial giant cell tumor (TGCT) - same pathological entity
- Benign but locally aggressive - causes cartilage and bone erosion through mechanical and enzymatic destruction
- Diffuse form has 30-50% recurrence despite complete synovectomy
- MRI characteristic: hemosiderin deposition causes blooming artifact on gradient echo sequences
- Treatment: Complete synovectomy + consider adjuvant (radiation, imatinib for CSF1R mutation)
Examiner's Pearls
- "PVNS and giant cell tumor of tendon sheath are the SAME disease - intra-articular vs extra-articular
- "Gold standard MRI finding: Low signal on T1 and T2 due to hemosiderin (blooming on GRE)
- "CSF1-COL6A3 fusion drives pathogenesis - CSF1R inhibitors (imatinib) for recurrent disease
- "Arthroscopic synovectomy alone has higher recurrence than open - consider adjuvant radiation
Critical PVNS Exam Points
Pathogenesis and Nomenclature
PVNS equals TGCT (tenosynovial giant cell tumor). Driven by CSF1-COL6A3 fusion causing CSF1 overexpression. This recruits inflammatory cells and creates the proliferative synovial mass.
Imaging Hallmark
Hemosiderin blooming on MRI. Low signal on T1 and T2 weighted sequences. Blooming artifact on gradient echo (GRE) sequences is pathognomonic for hemosiderin deposition.
Treatment Strategy
Complete synovectomy is key. Diffuse disease requires open or combined arthroscopic-open approach. Consider adjuvant radiation (20 Gy) or imatinib for recurrence prevention.
Recurrence Risk
Localized form recurs in under 10%. Diffuse form recurs in 30-50% despite complete excision. Recurrence peaks at 2-3 years post-op - long surveillance needed.
Quick Decision Guide - PVNS Management
| Presentation | Classification | Treatment | Key Pearl |
|---|---|---|---|
| Young adult, knee swelling, mechanical symptoms, discrete nodule | Localized (nodular) PVNS | Arthroscopic local excision | Low recurrence (under 10%) if complete excision |
| Young adult, chronic swelling, hemarthrosis, diffuse synovial thickening | Diffuse PVNS (villonodular) | Open synovectomy + consider adjuvant | High recurrence (30-50%) - counsel about surveillance |
| Recurrent disease after synovectomy, progressive joint destruction | Recurrent diffuse PVNS | Re-synovectomy + adjuvant (radiation or imatinib) | Consider CSF1R inhibitor (imatinib) for multiple recurrences |
HEMOSIDERINPVNS Pathological Features
Memory Hook:HEMOSIDERIN - the pathological pigment that defines PVNS on imaging and histology!
GIANTPVNS Differential Diagnosis
Memory Hook:GIANT cells are the histological hallmark - but remember the differentials!
RECURRecurrence Risk Factors for PVNS
Memory Hook:PVNS will RECUR unless you address these risk factors with complete excision and adjuvant therapy!
Overview and Epidemiology
Why PVNS Matters Clinically
PVNS (pigmented villonodular synovitis) is a rare benign proliferative disorder of the synovium that is locally aggressive and causes significant joint destruction if untreated. It is now recognized as part of the tenosynovial giant cell tumor (TGCT) spectrum - the same pathological process occurring intra-articularly (PVNS) versus extra-articularly (giant cell tumor of tendon sheath). Despite being benign, diffuse PVNS has high recurrence rates (30-50%) and can lead to premature arthritis requiring joint replacement in young adults.
Demographics
- Age: Peak incidence 20-40 years (young adults)
- Gender: Slight female predominance (1.5-2:1)
- Laterality: Usually monoarticular (95%)
- Race: No racial predilection
Clinical Impact
- Joint destruction: Progressive cartilage and bone erosion
- Recurrence: 30-50% for diffuse form despite synovectomy
- Disability: Chronic pain, swelling, mechanical symptoms
- Arthroplasty: May require joint replacement in young patients
The disease shows no hereditary pattern and no clear environmental or genetic risk factors have been identified. The hallmark is chronic monoarticular synovitis with recurrent hemarthrosis.
Pathophysiology and Molecular Biology
PVNS is Not Inflammatory - It's a Neoplastic Proliferation
Despite the name "synovitis", PVNS is NOT an inflammatory arthritis. It is a clonal neoplastic proliferation driven by CSF1-COL6A3 fusion causing CSF1 (colony stimulating factor 1) overexpression. CSF1 recruits inflammatory cells (macrophages, giant cells) that create the mass and cause joint destruction.
| Feature | Mechanism | Clinical Consequence |
|---|---|---|
| CSF1-COL6A3 fusion | Chromosomal translocation t(1;2) drives CSF1 overexpression | Neoplastic cells recruit inflammatory infiltrate |
| CSF1 overexpression | CSF1R on macrophages binds CSF1, recruiting inflammatory cells | Mass effect from macrophage and giant cell infiltration |
| Recurrent hemorrhage | Friable vascular tissue bleeds into joint | Hemosiderin deposition (iron) causes MRI blooming artifact |
| Enzymatic destruction | Macrophages release metalloproteases (MMPs) | Cartilage degradation and bone erosion |
Histopathology
- Multinucleated giant cells: Hallmark (but reactive, not neoplastic)
- Hemosiderin-laden macrophages: From recurrent hemorrhage
- Mononuclear stromal cells: The neoplastic component (CSF1 expressing)
- Foam cells: Lipid-laden macrophages
- Villous or nodular architecture: Synovial proliferation pattern
Targeted Therapy Rationale
- CSF1R inhibitors (imatinib, pexidartinib) block macrophage recruitment
- Effective for recurrent disease
- Reduces tumor burden and symptoms
- FDA-approved pexidartinib for TGCT (2019)
The key pathological distinction is localized versus diffuse forms, which have different prognosis and recurrence risk.
Classification and Clinical Forms
Localized (Nodular) PVNS
Clinical Features:
- Discrete nodular mass, often pedunculated
- Focal mechanical symptoms (locking, catching)
- Less hemarthrosis than diffuse form
- Better prognosis with local excision
Imaging:
- Well-defined lobulated mass
- Blooming artifact on GRE MRI
- Less extensive bone and cartilage erosion
Treatment:
- Arthroscopic local excision
- Lower recurrence (under 10%)
- No adjuvant therapy usually needed
Localized PVNS behaves more like a benign tumor amenable to complete excision.
Localized vs Diffuse - Prognostic Distinction
The critical exam point: Localized PVNS behaves like a benign tumor (low recurrence with complete excision), while diffuse PVNS behaves like a locally aggressive malignancy (high recurrence despite aggressive synovectomy). This distinction guides treatment intensity and patient counseling.
Clinical Presentation and Assessment
History
- Symptoms: Chronic joint swelling (months to years)
- Hemarthrosis: Recurrent bloody effusions (not traumatic)
- Pain: Dull aching pain, worse with activity
- Mechanical symptoms: Locking, catching (localized form)
- Stiffness: Progressive loss of range of motion
Examination
- Effusion: Chronic joint swelling, often tense
- Range of motion: Reduced, especially terminal flexion
- Palpable mass: May feel discrete nodule (localized)
- Synovial thickening: Diffuse boggy synovium (diffuse form)
- Instability: Usually absent (vs inflammatory arthritis)
PVNS Mimics Monoarticular Inflammatory Arthritis
Young adult with chronic monoarticular swelling and recurrent hemarthrosis - differential includes rheumatoid arthritis (RA), hemophilic arthropathy, tuberculous arthritis, and pigmented villonodular synovitis. The key distinguishing features: PVNS has hemosiderin blooming on MRI, lacks systemic inflammatory markers, and shows characteristic gross pathology (rust-brown synovium).
Joint Distribution:
- Knee (80% of cases) - most common site
- Hip (10-15%) - more challenging diagnosis and treatment
- Ankle, shoulder, elbow (rare, each under 5%)
- Temporomandibular joint (case reports)
The key clinical clue is monoarticular chronic synovitis with recurrent hemarthrosis in a young adult.
Imaging and Diagnosis
Diagnostic Imaging Protocol
Initial assessment: May show soft tissue swelling, joint effusion, bone erosions (late finding). Often normal in early disease.
Key findings:
- Soft tissue mass (if large)
- Bone erosions on both sides of joint (subchondral cysts)
- Preserved joint space (until late)
- No calcification (unlike synovial chondromatosis)
Diagnostic MRI features: Low signal on T1 and T2 weighted sequences due to hemosiderin. Blooming artifact on gradient echo (GRE) or susceptibility-weighted imaging (SWI) is pathognomonic.
Sensitivity/Specificity: Over 90% for PVNS diagnosis when blooming artifact present.
Additional findings:
- Synovial thickening (nodular or diffuse)
- Joint effusion (often bloody)
- Bone erosions with sclerotic margins
- Extent of disease (critical for surgical planning)
Appearance: Bloody or serosanguinous (not clear)
Cytology: Hemosiderin-laden macrophages, multinucleated giant cells, mononuclear cells
Role: Exclude infection, crystal arthropathy, inflammatory arthritis
Indications: Atypical imaging, need to exclude malignancy
Approach: Arthroscopic synovial biopsy (safe, diagnostic)
Histology confirms: Hemosiderin, giant cells, mononuclear stromal cells
MRI Blooming Artifact - Pathognomonic Finding
Q: What is the characteristic MRI finding in PVNS? A: Blooming artifact on gradient echo (GRE) sequences - caused by hemosiderin (iron) deposition from recurrent hemorrhage. This produces susceptibility artifact with signal dropout (blooming) that is much larger than the actual lesion size on GRE images. Low signal on T1 and T2 is also characteristic.
Differential Diagnosis
PVNS Differential Diagnosis
| Condition | Key Distinguishing Features | Imaging Differences |
|---|---|---|
| Giant cell tumor of tendon sheath | Extra-articular location (tendon sheath), same histology as PVNS | No intra-articular involvement, no blooming (usually) |
| Synovial chondromatosis | Calcified loose bodies, no hemosiderin, younger age | Calcifications on XR, high signal on T2, no blooming |
| Hemophilic arthropathy | Known hemophilia, recurrent hemarthrosis, factor deficiency | Similar MRI findings, but systemic disease and clotting history |
| Rheumatoid arthritis | Polyarticular, positive RF/anti-CCP, systemic inflammation | Synovial enhancement, erosions, no blooming artifact |
| Synovial sarcoma | MALIGNANT, aggressive bone destruction, rapid growth | Heterogeneous enhancement, invasion, calcification (30%) |
| Tuberculous arthritis | Chronic monoarthritis, systemic TB symptoms, positive cultures | Synovial enhancement, erosions, rice bodies, no blooming |
The critical distinction is benign (PVNS, chondromatosis) versus malignant (synovial sarcoma) - biopsy if any doubt.
Management Algorithm
Localized PVNS Management
Goal: Complete excision of nodule with preservation of joint function.
Treatment Steps
Approach: Arthroscopic local excision of nodule (with margin)
Technique:
- Visualize entire nodule and stalk
- Excise with 2-3mm margin of normal synovium
- Remove in toto if possible (avoid fragmentation)
- Hemostasis critical (prevent recurrent bleeding)
Success rate: Over 90% cure with complete excision
Indications: Large nodule, difficult location (posterior knee, hip)
Approach: Mini-arthrotomy or formal arthrotomy
Advantage: Better visualization and complete excision
Protocol: Clinical and MRI surveillance every 6-12 months for 3 years
Recurrence: Under 10% for localized form
Management of recurrence: Re-excision, consider adjuvant
Localized PVNS has excellent prognosis with complete excision and low recurrence.
Complete Synovectomy is Key - But Recurrence is Common
The paradox of diffuse PVNS: Complete synovectomy is the goal and reduces recurrence, but even with "complete" excision, recurrence rates are 30-50%. This is because microscopic disease is often left behind, and the CSF1-driven proliferation can restart. Patients must be counseled about high recurrence risk and need for long-term surveillance.
Surgical Technique - Open Total Synovectomy (Knee)
Patient Positioning and Setup
Setup Checklist
Supine on standard operating table.
- Tourniquet on proximal thigh
- Leg free-draped from tourniquet distally
- Lateral post at foot of table for valgus stress
- Contralateral leg secured and padded
- Heel free of bed (prevent pressure injury)
- Tourniquet padding adequate
- No fluoroscopy needed for synovectomy
- Pre-operative MRI reviewed in OR for extent of disease
Standard positioning for knee arthrotomy.
Recurrence and Surveillance
| Factor | Localized PVNS | Diffuse PVNS |
|---|---|---|
| Recurrence rate | Under 10% | 30-50% |
| Time to recurrence | 1-2 years (median) | 2-3 years (median) |
| Recurrence risk factors | Incomplete excision, fragmentation | Diffuse involvement, posterior disease, hip location |
| Surveillance protocol | MRI every 6-12 months for 3 years | MRI every 6 months for 5 years |
Recurrence is the Major Challenge in Diffuse PVNS
Key counseling point: Even with complete synovectomy, diffuse PVNS recurs in 30-50% of cases. Recurrence typically occurs at 2-3 years post-op. Patients need long-term MRI surveillance (every 6 months for 5 years). Early recurrence detection allows re-synovectomy before extensive joint destruction occurs.
Management of Recurrent PVNS:
- First recurrence: Re-synovectomy + adjuvant radiation (20 Gy)
- Multiple recurrences: Consider CSF1R inhibitor (pexidartinib, imatinib)
- Unresectable disease: CSF1R inhibitor or arthroplasty
The goal is to balance aggressive treatment with preservation of joint function.
Complications of PVNS and Treatment
| Complication | Incidence/Risk Factors | Prevention/Management |
|---|---|---|
| Recurrence (most common) | 30-50% for diffuse PVNS, under 10% for localized | Complete synovectomy, adjuvant radiation, long surveillance |
| Progressive joint destruction | Untreated or recurrent disease causes cartilage and bone erosion | Early diagnosis and complete excision critical |
| Postoperative hemarthrosis | PVNS tissue is vascular, risk of bleeding after synovectomy | Meticulous hemostasis, drain placement, monitor drain output |
| Knee stiffness | After extensive synovectomy or radiation | Early range of motion, physiotherapy |
| Hepatotoxicity (pexidartinib) | CSF1R inhibitor can cause liver injury | Liver function test monitoring, dose adjustment or discontinuation |
| End-stage arthritis | Recurrent disease or delayed diagnosis | Total joint arthroplasty as salvage (young age is challenging) |
Hepatotoxicity with Pexidartinib - Black Box Warning
Key monitoring requirement: Pexidartinib (CSF1R inhibitor) carries FDA black box warning for hepatotoxicity. Liver function tests (LFTs) must be monitored before, during, and after treatment. Severe or progressive liver enzyme elevation requires dose reduction or discontinuation. This limits use to recurrent or unresectable PVNS where benefit outweighs risk.
The major complication of PVNS is recurrence, which drives need for surveillance and adjuvant therapy strategies.
Postoperative Care and Rehabilitation
Immediate Postoperative Management (Days 0-7)
Early Recovery Protocol
- Pain control: Multimodal analgesia (opioids, NSAIDs, ice)
- Drain management: Monitor output (remove at 24-48h when decreasing)
- DVT prophylaxis: Aspirin or LMWH per protocol
- Mobilization: Bed to chair, weight-bearing as tolerated
- Wound care: Monitor for bleeding, infection
- Range of motion: Start gentle passive ROM to prevent stiffness
- Mobilization: Crutches for comfort, full weight-bearing
- Discharge planning: Home with physiotherapy referral
Early range of motion is critical to prevent stiffness after extensive synovectomy.
Surveillance Schedule
- Localized PVNS: MRI every 6-12 months for 3 years
- Diffuse PVNS: MRI every 6 months for 5 years
- Clinical exam: At each imaging visit (assess ROM, swelling, function)
- Baseline: Post-op MRI at 6 months (compare future scans to this)
Red Flags - Recurrence
- Recurrent swelling: New or worsening joint effusion
- Mechanical symptoms: Locking, catching (new nodule)
- Pain: Progressive pain not explained by arthritis
- MRI: Synovial thickening, blooming artifact reappears
Long-term surveillance is essential given high recurrence risk in diffuse PVNS.
Outcomes and Prognosis
| Form | Treatment | Recurrence Rate | Long-Term Outcome |
|---|---|---|---|
| Localized PVNS | Local excision | Under 10% | Excellent - over 90% retain full function |
| Diffuse PVNS (synovectomy alone) | Open total synovectomy | 30-50% | Good if no recurrence, but recurrence common |
| Diffuse PVNS (synovectomy + radiation) | Synovectomy + 20 Gy XRT | 15-20% | Better than synovectomy alone, some stiffness risk |
| Recurrent PVNS (CSF1R inhibitor) | Pexidartinib or imatinib | Disease stabilization/shrinkage | Palliative - not curative, requires ongoing therapy |
Prognostic Factors - What Predicts Recurrence?
Poor prognostic factors (higher recurrence risk):
- Diffuse form (vs localized)
- Hip location (vs knee)
- Incomplete synovectomy (residual disease)
- Arthroscopic approach for diffuse disease (vs open)
- Young age (longer follow-up allows recurrence detection)
Good prognostic factors:
- Localized nodular form
- Complete excision with margins
- Open synovectomy (vs arthroscopic for diffuse)
- Adjuvant radiation (reduces recurrence by 50%)
The key message: PVNS is a chronic disease requiring long-term surveillance, but outcomes are generally good if recurrence is detected and treated early.
Evidence Base and Key Studies
PVNS Recurrence After Synovectomy: Systematic Review
- Systematic review of 474 patients with PVNS
- Localized PVNS recurrence: 8% (arthroscopic) vs 4% (open)
- Diffuse PVNS recurrence: 46% (arthroscopic) vs 18% (open)
- Median time to recurrence: 2.4 years
- Adjuvant radiation reduced recurrence by 50% in diffuse disease
CSF1-COL6A3 Fusion in Tenosynovial Giant Cell Tumor
- Identified CSF1-COL6A3 fusion in PVNS/TGCT specimens
- Chromosomal translocation t(1;2) drives CSF1 overexpression
- CSF1 recruits inflammatory cells (macrophages) via CSF1R
- Established molecular pathogenesis of PVNS
Pexidartinib for Advanced TGCT: Phase 3 ENLIVEN Trial
- Randomized trial: pexidartinib vs placebo in 120 patients with TGCT
- Overall response rate: 39% vs 0% (placebo)
- Tumor volume reduction at 24 weeks in 56% vs 0%
- FDA approval for TGCT in 2019
- Hepatotoxicity black box warning
Role of Adjuvant Radiation in PVNS
- Systematic review of radiation therapy for PVNS
- External beam radiation (20 Gy) reduces recurrence from 50% to 15-20%
- Most effective as adjuvant after incomplete synovectomy
- Complications: Joint stiffness (15%), wound issues (5%)
- No long-term malignancy risk observed at 20 Gy dose
MRI Features of PVNS - Blooming Artifact Specificity
- Review of 57 PVNS cases with MRI correlation
- Blooming artifact on GRE sequences: 94% sensitivity, 90% specificity
- Low signal on T1 and T2 in 88% of cases (hemosiderin)
- Differential: hemophilia, amyloid also show blooming (but clinical history different)
- MRI accuracy for local vs diffuse classification: 85%
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Young Adult with Chronic Knee Swelling
"A 28-year-old female presents with 18 months of progressive left knee swelling and recurrent episodes of joint effusion. She describes the fluid as 'bloody' when aspirated previously. MRI shows diffuse synovial thickening with low signal on T1 and T2, and blooming artifact on gradient echo sequences. What is your diagnosis and management?"
Scenario 2: Surgical Technique for Diffuse PVNS
"You have decided to proceed with open total synovectomy for diffuse PVNS of the knee. Walk me through your surgical approach and key steps."
Scenario 3: Recurrent PVNS Management
"A 35-year-old male had open total synovectomy for diffuse PVNS of the knee 2 years ago. He now presents with recurrent swelling and MRI shows synovial thickening in the suprapatellar pouch and medial gutter consistent with recurrent disease. How do you manage this?"
MCQ Practice Points
Pathogenesis Question
Q: What is the molecular driver of PVNS/TGCT? A: CSF1-COL6A3 fusion causing CSF1 overexpression. The chromosomal translocation t(1;2) drives colony stimulating factor 1 (CSF1) overexpression, which recruits inflammatory cells (macrophages, giant cells) via CSF1R. This is the rationale for CSF1R inhibitor therapy.
Imaging Question
Q: What is the pathognomonic MRI finding in PVNS? A: Blooming artifact on gradient echo (GRE) sequences - caused by hemosiderin (iron) deposition from recurrent hemorrhage. Also low signal on T1 and T2 weighted images. This finding has over 90% sensitivity and specificity for PVNS.
Classification Question
Q: What is the difference between localized and diffuse PVNS in terms of recurrence? A: Localized PVNS recurs in under 10% after complete excision (behaves like benign tumor). Diffuse PVNS recurs in 30-50% despite complete synovectomy (behaves like locally aggressive lesion). This distinction is critical for counseling and treatment planning.
Treatment Question
Q: What is the role of adjuvant radiation in diffuse PVNS? A: Adjuvant external beam radiation (20 Gy) reduces recurrence from 50% to approximately 20% in diffuse PVNS. Indicated for high recurrence risk (diffuse disease, incomplete excision, recurrent disease). Complications include stiffness and wound healing issues.
Targeted Therapy Question
Q: What is pexidartinib and its indication? A: Pexidartinib is a CSF1R inhibitor FDA-approved for TGCT (PVNS) in 2019. Indicated for recurrent or unresectable disease. Mechanism: blocks CSF1R, preventing macrophage recruitment. Efficacy: 50-60% tumor shrinkage in recurrent disease. Key complication: hepatotoxicity (black box warning) - requires liver function monitoring.
Australian Context and Medicolegal Considerations
Rare Disease Registries
- No specific AOANJRR data for PVNS (not joint replacement)
- Consider enrollment in Australian Sarcoma Study Group for tumor-like lesions
- National registry data limited for PVNS
- International collaboration (European TGCT registry) provides epidemiology
Access to Targeted Therapy
- Pexidartinib: Not PBS-listed in Australia (expensive, ~$150,000/year)
- Requires special access scheme or compassionate use
- Imatinib: PBS-listed for GIST, can be used off-label for TGCT
- Multidisciplinary tumor board review for recurrent disease
Medicolegal Considerations and Consent
Key documentation requirements for PVNS surgery:
- Recurrence risk: Must counsel diffuse PVNS patients about 30-50% recurrence despite complete excision
- Incomplete excision: Document intraoperative assessment of completeness, MRI findings
- Adjuvant therapy options: Discuss radiation vs observation for diffuse disease
- Surveillance: Clear plan for follow-up MRI and duration
- Arthroplasty risk: Counsel young patients about potential for future joint replacement if recurrent
Common litigation scenarios:
- Failure to diagnose (delayed MRI, missed blooming artifact)
- Inadequate synovectomy (arthroscopic for diffuse disease)
- Lack of adjuvant therapy discussion (patient not offered radiation)
- Inadequate surveillance (recurrence missed, progresses to arthritis)
Multidisciplinary Management
- Orthopaedic oncology: Diagnosis and surgical management
- Radiology: MRI expertise for diagnosis and surveillance
- Pathology: Histological confirmation, rule out malignancy
- Radiation oncology: Adjuvant radiation planning
- Medical oncology: CSF1R inhibitor therapy for recurrent disease
Patient Support
- Cancer Council resources (tumor-like lesions)
- Musculoskeletal Australia for chronic joint disease
- Online TGCT patient support groups
- Clear communication about benign nature (not cancer)
PVNS management in Australia requires coordination across multiple specialties, particularly for recurrent disease requiring targeted therapy.
PIGMENTED VILLONODULAR SYNOVITIS (PVNS)
High-Yield Exam Summary
Key Pathology
- •PVNS equals TGCT (tenosynovial giant cell tumor) - same disease, different location
- •CSF1-COL6A3 fusion drives CSF1 overexpression = macrophage recruitment
- •Histology: Hemosiderin-laden macrophages, multinucleated giant cells, mononuclear stromal cells
- •Gross: Orange-brown synovium (from hemosiderin = recurrent hemorrhage)
Classification
- •Localized (nodular) = discrete mass = excision = under 10% recurrence
- •Diffuse (villonodular) = entire synovium = synovectomy = 30-50% recurrence
- •Knee 80%, hip 10-15%, other joints rare
Imaging
- •MRI blooming artifact on GRE = pathognomonic (hemosiderin)
- •Low signal T1 and T2 = hemosiderin deposition
- •Bone erosions with sclerotic margins (late finding)
- •Synovial thickening (nodular or diffuse)
Treatment Algorithm
- •Localized: Arthroscopic local excision (under 10% recurrence)
- •Diffuse: Open total synovectomy (30-50% recurrence despite complete excision)
- •Adjuvant radiation: 20 Gy reduces recurrence from 50% to 20%
- •Recurrent/unresectable: CSF1R inhibitor (pexidartinib, imatinib)
Surgical Pearls
- •Complete synovectomy: Suprapatellar pouch, gutters, intercondylar notch, posterior capsule
- •Posterior approach if extensive posterior disease on MRI
- •Meticulous hemostasis (vascular tissue) - large bore drain
- •Danger: Popliteal vessels posterior, cruciate ligaments in notch