To the Editor:

I read with interest the following article "Visco-supplementation Pseudotumor: A Case Report", by Jones, et al. (1) Contrary to the conclusion reached by the authors, I believe that the misdiagnosed soft tissue mass was due to a ruptured, pre- existing popliteal cyst and cannot be attributed to any unique properties of Synvisc(R).

Popliteal cysts are common in patients with cartilage lesions (2), OA of the knee joint (2-4), meniscal lesions (2-5), and meniscal tears (2-5), or they may occur spontaneously without intra-articular pathology (2). Some treatment options focus on treating the associated intra-articular pathology rather than the cyst itself (4). Popliteal cysts also are difficult to detect because they can be asymptomatic, too small to detect during physical examination, or may have symptoms that blend with those from the intra- articular pathologies (2,6-8). Popliteal cysts usually persist and may leak or rupture (2).

The investigators acknowledge, and I believe, that the soft tissue mass initially diagnosed as a tumor, may have developed as a result of a pre-existing popliteal cyst that became inflamed and ruptured, an event commonly seen in my practice of knee disorders. The study patient had advanced osteoarthritis of the knee joint, a complex medial meniscal tear, and symptoms and findings commonly associated with a ruptured popliteal cyst. These observations support the likelihood that this patient had a pre-existing popliteal cyst. An injection of any substance in the knee joint, in this case Synvisc(R), may have exacerbated the existing popliteal inflammation. Two subsequent injections of Synvisc(R), in the presence of increased inflammation, may have caused the patient's condition to worsen. The incorrect diagnosis of a tumor was unfortunate and resulted in a delay in diagnosis that allowed the ruptured cyst to organize into a soft tissue mass. While Synvisc(R) is generally safe, physicians who observe persistent local inflammation after treatment with Synvisc(R) should delay subsequent injections until complete resolution of inflammation. Although it is always important to be thorough in establishing a differential diagnosis, one should always first consider the unusual presentation of a common problem rather than the rare unusual diagnosis. I thank the authors for this interesting and educational case report.

Sincerely yours,

Nicholas A. DiNubile, M.D., Chief of Orthopaedic Surgery, Delaware County Memorial Hospital

References:

(1) Jones KB, Patel PP, DeYoung BR, Buckwalter JA. Visco supplementation pseudotumor. A case report. J Bone and Joint Surg Am. 2005; 87:1113-9.

(2) Handy JR. Popliteal cysts in adults: a review. Semin Arthritis Rheum. 2001; 31:108-18.

(3) Hill CL, Gale DG, Chaisson CE, Skinner K, Kazis L, Gale Me et ala Knee effusions, popliteal cysts, and synovial thickening: Association with knee pain in osteoarthritis. J Rheumatol. 2001; 28:1130-337.

(4) Rupp S, Sell R, Jochum P, Kohn D. Popliteal cysts in adults: prevalence, associated intraarticular lesions, and results after arthroscopic treatment. Am J SportsMed 2002; 30:112-5.

(5) Stone KR, Stoller D, Carli AD. The frequency of Baker's cysts associated with meniscal tears. Am J Sports Med 1996; 24:670-1.

(6) Burleson RJ, Bickel WH, Dahlin DC. Popliteal cyst: a clinicopathologic study. J Bone andJoint Surg Am. 1956; 38A:1265-74.

(7) Fam AD, Wilson SR, Holmberg S. lTItrasound evaluation of popliteal cysts in osteoarthritis of the knee. J Rheumatol. 1982; 9:428- 34.

(8) Rauschning W, Lindgren PG. Popliteal cysts (Baker's cysts) in adults. Clinical and roentgenological results of operative excision. Acta Orthop Scand 1979; 50:583-91.