What is the recommended first‑line treatment for pigmented villonodular synovitis of the knee in an adult?

Treatment for Knee Pigmented Villonodular Synovitis

For localized PVNS of the knee, arthroscopic synovectomy with complete excision of the lesion is the first-line treatment, achieving 100% success rates without recurrence. 1

Differentiation by Disease Pattern

The treatment approach fundamentally depends on whether the disease is localized (nodular) or diffuse:

Localized (Nodular) PVNS

• Arthroscopic partial synovectomy with complete excision of the nodular lesion is the standard treatment, with excellent prognosis and minimal recurrence rates. 1, 2, 3
• This approach offers lower morbidity compared to open procedures while maintaining excellent outcomes. 4
• For posterior compartment nodules that are arthroscopically inaccessible, open excision remains necessary to ensure complete removal. 4

Diffuse PVNS

• Combined anterior arthroscopic and open posterior synovectomy is the preferred surgical approach for diffuse disease involving the entire synovium. 4
• Total synovectomy should be the treatment of choice, though recurrence rates up to 46% are reported even with complete excision. 2, 3
• The technically demanding nature of total arthroscopic synovectomy requires maximizing access using transcondylar notch views, accessory posterior portals, and posterior transseptal portals. 5

Surgical Technique Considerations

• Excision must be performed in sound tissue with oncologically appropriate margins to minimize recurrence risk. 2
• Open synovectomy carries risks of arthrofibrosis and wound breakdown, making arthroscopic approaches preferable when technically feasible. 5, 3
• Synovectomy by any approach may prevent secondary osteoarthritis and subsequent need for joint arthroplasty. 3

Adjuvant and Alternative Therapies

For Unresectable or Recurrent Disease

• Imatinib should be considered for progressive symptomatic disease that is not surgically resectable, as it induces tumor stabilization or reduction and alleviates associated morbidity. 1
• Intra-articular radioisotope injection (⁹⁰Y synoviorthesis) and external beam radiation may provide benefit as adjuvant therapy for extensive diffuse or recurrent PVNS. 2, 5
• Combined surgical and nonsurgical approaches may be necessary for complex cases. 3
• Radiation therapy has re-emerged as an adjuvant option, though potential serious toxicity makes it questionable for such a benign condition. 4

Non-Surgical Options (Limited Role)

• Steroid injections have shown some benefit in selected patients but are not first-line treatment. 2
• Novel small molecule and monoclonal antibody targeted therapies are under investigation with promising early results. 4

Follow-Up Protocol

• Surveillance must include periodic clinical evaluation and MRI, which is the gold standard for detecting recurrence. 1
• MRI with gradient echo sequences showing characteristic intra-articular masses with signal dropout on T2-weighted images confirms diagnosis and monitors treatment response. 6
• At 15-month average follow-up, 88% of patients remain disease-free based on clinical examination and/or follow-up MRI. 6

Critical Pitfalls to Avoid

• Do not rely on radiographs alone—they are often unremarkable or show only nonspecific findings like bone lesions in 40% of cases. 2
• Do not misdiagnose as rheumatoid arthritis or other inflammatory arthropathies—more than half of pediatric patients are initially misdiagnosed with rheumatologic conditions, bleeding disorders, or septic arthritis. 6
• Do not perform incomplete excision—partial removal of diffuse disease leads to high recurrence rates. 3
• Do not delay diagnosis—average symptom duration before correct diagnosis is 16-24 months, allowing disease progression. 2, 6
• In cases where total joint arthroplasty becomes necessary due to advanced disease or failed prior treatments, this represents the definitive salvage option. 3