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SUBACUTE KNEE PAIN IS NOT ALWAYS WHAT IT SEEMS. Steven R. Sabo, MD Sports Medicine Fellow 2011-2012 University of South Florida and Morton Plant Mease / BayCare Health System. History of Present I llness.

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Subacute knee pain is not always what it seems


Steven R. Sabo, MD

Sports Medicine Fellow 2011-2012

University of South Florida and

Morton Plant Mease / BayCare Health System

History of present i llness

History of Present Illness

  • 36 y.o. male softball player and auto mechanic c/o right knee pain, stiffness, and swelling x 3 months

  • Twisted right knee walking down stairs.

  • Posterior knee joint 6/10 pain, increases with any knee flexion.

  • No giving way, locking, or prior Hx of trauma.

R knee injury x 3 months

R knee Injury x 3 months

  • MHX/SHX: Prior left knee sprain 1 yr ago resolved. No chronic injuries or diseases.

  • Meds: None Allergies: Pen causes rash.

  • Exam: 6/10 Pain @ deep popliteal fossa,

    Moderate size joint effusion without warmth

    No joint line tenderness

    ROM decreased (only 10 to 130 degrees)

    Equivocal Thessaly test

    No ligament defect noted on stress tests

Differential diagnosis

Differential Diagnosis:

  • Meniscal tear with effusion

  • Baker’s cyst

  • partial ACL/PCL ligament injury with effusion

  • Osteoarthritis, loose body, Stress fracture.

  • infectious arthritis, gout or pseudogout

  • RA autoimmune arthritis, psoriatic or seronegative arthritis, amyloidosis, SLE

Imaging and special studies

Imaging and Special Studies:

  • X-rays revealed mild osteoarthritis

  • CBC, ESR, CRP, RF and ANA ordered by PCM and were normal

  • Aspiration of knee = 10 ml of blood tinged “rusty” colored synovial fluid without evidence of crystals, infection, or malignant cells.

  • Stiffness and effusion recurred rapidly before the next day

  • Sports Med / Ortho ordered an MRI.

Mri of right knee

MRI of Right Knee

  • Diffuse non-calcified nodular synovial thickening

  • 8.5 cm diameter Baker’s popliteal cyst

  • Chondromalacia Patella, mild diffuse

  • No ligament derangement, meniscal tear, fracture, or bone contusion.

New differential diagnosis

New Differential Diagnosis:

  • Synovial Chondromatosis

  • Chronic Hemarthrosis

  • Rheumatoid Arthritis

  • Pigmented Villonodular Synovitis

  • Benign fibroblastic tumors

Surgery and pathology results

Surgery and Pathology Results:

  • Exploratory open arthrotomy with synovectomy done because of MRI findings.

  • Dark Red 16 x 12 x 6 cm large lobulated mass immediately extruded from the surgical wound as if under pressure.

  • Multiple lesions had eroded partially into the undersurface and margins of the patella.

  • Pathology: hypervascular proliferative synovium containing multinucleated giant cells, macrophages, and hemosiderin.

Normal synovium vs pigmented villonodular synovitis

Normal Synovium vs.Pigmented Villonodular Synovitis

  • NormalPVNS

Final diagnosis pigmented villonodular synovitis pvns

Final Diagnosis:Pigmented Villonodular Synovitis (PVNS)

  • Treatment: Synovectomy for complete removal of lesion, post-op hinged knee brace, then physical therapy.

  • Outcome: Patient had return of normal joint function. Normal ROM and strength. No recurrence of pain or effusion @ 6 months

  • PX: Diffuse PVNS recurs up to 46%, Localized PVNS recurs at 8%

Tx options for recurrence

Tx options for recurrence

  • Repeat Synovectomy

  • XRT Radiation Therapy 4000 cGy

  • If enough of joint is destroyed: bone grafting or total joint replacement

  • Tumor Necrosis Factor αinhibitor (class of drugs): off label use to decrease inflammatory response for refractory PVNS, reported in Rheumatology case studies. Examples: etanercept (Enbrel), infliximab (Remicade), adalimumab (Humira).

Take home messages

Take Home Messages:

  • Relatively rare (incidence 1.8 cases/ million people), usually benign intra-articular and peri-articular hyperproliferation of synovium

    Cause debated: malignant transformation vs. chronic inflammatory

  • Removal of the lesion is usually curative

  • Repeat imaging is prudent since it recurs

  • Important to occasionally widen your DDX for knee pain.

Special thanks

Special Thanks:

Our patient (written consent given to allow this case report)

Allen Hughes, MD

Orthopedic Specialties of Clearwater FL

Sean Bryan, MD

USF / MPM Sports Medicine Fellowship and

Family Medicine Residency Program Director

Ted Farrar, MD

USF / MPM Sports Medicine Fellowship Associate Director

Jonathan Squires, MD

Radiology Associates of Clearwater FL

Robert Schoer MD and Pathology Department

Morton Plant Mease Medical Center Clearwater FL

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