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Tuesday, January 20, 2009

BAKER CYST

BAKER CYST - Gregory R. Czarnecki, DO; John Herbert Stevenson, MD
BASICS
DESCRIPTION
• Aka popliteal cyst; a fluid-filled synovial-lined sac (cyst) arising in the popliteal fossa
• Can be unilateral or bilateral
• Found in both children and adults
EPIDEMIOLOGY
Bimodal distribution: Children 4-7 and adults increasing with age
Prevalence
• Varies by study
• 2.4% in asymptomatic children in 1 prospective study (1)[B]
• 5% in adults by MRI in 1 prospective study; up to 58% in others, limited by sample population and largely retrospective data (2)[B]
RISK FACTORS
• Knee osteoarthritis
• Rheumatoid arthritis
• Meniscal degeneration/tear
• Advancing age
ETIOLOGY
• Extension or herniation of synovial membrane of the knee joint capsule or connection of normal bursa with the joint capsule. This may be the result of increased intraarticular pressure and is commonly seen in association with knee effusions. Direct trauma to the bursa may be the primary cause in children.
• A valvelike mechanism has been described with this connection of bursa and joint allowing primary one-way passage of fluid from the joint to the bursal connection.
• Associated intraarticular pathological findings are rare in children but common in adultsup to 50%. (3)[B]
• Bursa under the medial head of the gastrocnemius or semimembranosus bursa most commonly involved
ASSOCIATED CONDITIONS
• Osteoarthritis
• Rheumatoid arthritis
• Meniscal tear, notably posterior horn of medial meniscus


DIAGNOSIS
SIGNS AND SYMPTOMS
History
• (Often) painless mass arising in the popliteal fossa
• May complain of restricted range of motion or tightness with knee flexion
• Ruptured cyst typically painful with associated swelling causing pseudothrombophlebitis
• Large cysts may cause entrapment neuropathy of the tibial nerve.
• Vascular compression may produce claudication.
Physical Exam
• Examine in full extension and 90 flexion. Mass increases with extension and may disappear on flexion (Foucher sign).
• Most commonly found in medial popliteal fossa
• Mass may be fluctuant or tender
• Transillumination to distinguish cystic vs. solid
TESTS
Imaging
• Ultrasound readily confirms presence and size.
• MRI allows further characterization of association with joint capsule.
• May also detect on arthrography or CT scan
• Radiographs may show soft tissue density posteriorly.
Diagnostic Procedures/Surgery
Arthrography may demonstrate communication with joint capsule.
DIFFERENTIAL DIAGNOSIS
• Aneurysm
• Deep venous thrombosis
• Infection/abscess
• Lipoma
• Fibroma
• Fibrosarcoma
• Hematoma
• Vascular tumor
• Xanthoma
• Any condition causing synovitis
TREATMENT
GENERAL MEASURES
• No treatment if aysmptomatic
• Compressive wrap or sleeve may be used for comfort
• Treat underlying cause if present, (e.g., intraarticular derangement)
Activity
No restrictions
SPECIAL THERAPY
• Aspiration for symptom relief, recurrance common
• Injection with corticosteroid directly into cyst following aspiration, or intraarticular if communicating cyst. If joint communication is present, intraarticular corticosteroid injection may assist regression of cyst. (3)[B]
Physical Therapy
Physical therapy is helpful in improving knee range of motion and strength. It is also helpful if co-existing knee arthritis or stable meniscal tear.
MEDICATION (DRUGS)
Analgesics, NSAIDS for symptomatic relief.
SURGERY
Excision via arthroscopy or open procedure often requires treatment of intraarticular pathology (when present) to prevent recurrence of cyst. (3)[B]
FOLLOW-UP
Routine monitoring providing diagnosis is clear. Size of cyst may vary depending on degree of knee effusion and joint communication.
DISPOSITION
Issues for Referral
Consider whether definitive treatment desired. Despite surgical removal, some cysts recur; treatment of underlying intraarticular pathology, if present, is imperative.
PROGNOSIS
• Variable
• Many cysts remain asymptomatic, and some will regress or resolve with treatment of associated cause without direct treatment of the cyst; in others, size may remain stable or expand; recurrence is common.
• In children, most resolve without treatment.
COMPLICATIONS
• Compartment syndrome in ruptured cyst
• Pain with cyst expansion/dissection or rupture
• Frequent recurrence
PATIENT MONITORING
See above
REFERENCES
1. Seil R, Rupp S, et al. Prevalence of popliteal cysts in children: A sonographic study and review of the literature. Arch Ortho Traum Su. 1999;119:73-75.
2. Rupp S, Seil R, et al. Popliteal cysts in adults: prevalence, associated intraarticular lesions, and results after arthroscopic treatment. Am Sport Med. 2002;30(1):112-115.
3. Handy JR. Popliteal cysts in adults: A review. Semin Arthritis Rheu. 2001;31(2):108-118.
4. Canale. Campbell's Operative Orthopaedics, 10th ed., Mosby, Inc. 2003;894-903.

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