The Knee 14 (2007) 164–166

Short communication

Glomus tumor beneath the plica synovialis in the knee: A case report

Satoshi Kato ⁎, Hideto Fujii, Akira Yoshida, Shigeru Hinoki

Department of Orthopaedic Surgery, Toyama-ken Saiseikai Toyama Hospital, 33-1 Kusunoki, Toyama, 931-8533, Japan

Received 23 July 2006; received in revised form 15 November 2006; accepted 19 November 2006

Abstract

Glomus tumors are rare benign tumors distinguished clinically by their small size and ability to cause extreme pain. These lesions are usuallyfound beneath the fingernails. Atypical locations of the tumor are difficult to diagnose, especially when the lesion is situated in a deep anatomicstructure. We describe a 33-year-old man with glomus tumor beneath the plica synovialis in the knee. He had experienced right knee pain for10 years which increased withmovements of the knee. There was a point of tenderness on palpation at the lateral aspect of the knee. CTscanwitharthrography showed a smallmass on the lateral femoral condyle in the joint space. It was seen retrospectively inMRI. Arthroscopy demonstratedthe soft tissuemass beneath the plica synovialis.Wemade a separate incision and removed it completely. An immediate disappearance of the painwas observed after surgery. Histology was the glomus tumor of the vascular type. The tumor seemed to be stimulated by the plica synovitis or thelateral joint capsule and it caused pain on motion similar to meniscal tear. There has been no recurrence for 3 years after surgery.© 2007 Published by Elsevier B.V.

Keywords: Glomus tumor; Knee; Plica synovialis; CT scan with arthrography; MRI

Glomus tumor, first described in detail by Masson, is arare benign tumor from the neuromyoarterial canal systemcalled the Sucquet–Hoyer canals of the glomus body in theskin [4]. The normal glomus body is a specialized form ofarteriovenous anastomosis that serves thermal regulation. Itis located in the stratum reticularis of the dermis and is mostfrequently encountered in the subungual region. Glomustumors are typically found in the subungual region, butseveral glomus tumors around the knee have been reported.Most were located in subcutaneous tissue, some involved thepatellar ligament [3] and the fat pad [1] but there are noprevious reports of glomus tumors localized beneath thesynovial membrane in the knee joint. This case reportdescribes for the first time a case of glomus tumor beneaththe plica synovialis in the knee joint.

1. Case report

A 33-year-old man presented to our hospital complainingof pain in the lateral side of the right knee. He reported a

⁎ Corresponding author. Tel.: +81 76 437 1111; fax: +81 76 437 1122.E-mail address: inji@par.odn.ne.jp (S. Kato).

0968-0160/$ - see front matter © 2007 Published by Elsevier B.V.doi:10.1016/j.knee.2006.11.013

history of approximately 10 years with worsening over therecent 3 years. There was no history of trauma. Painincreased with movements of the right knee, such as walkingor squatting. It was relieved by resting, especially when theknee was slightly flexed.

Physical examination of the knee revealed a point oftenderness on palpation, localized 2 cm higher than thelateral joint line. There was no inflammatory sign or laxity ofthe joint, no palpable mass, and though the pain wasincreased by meniscus test, typical sign of meniscus lesionwas absent. The knee had a normal range of motion. Thecircumference of the right thigh was 3 cm smaller than that ofthe left thigh. Pain was not calmed temporarily by anestheticinjection into the suprapatellar bursa.

Plain radiographs did not show any remarkable change.MRI showed a lateral discoid meniscus without tear. We didnot assume that the symptom was caused by the discoidmeniscus, therefore CT scan with arthrography(air 50 ml andisobist 3 ml) was performed to detect an unknown lesion inthe joint space. A small soft tissue mass was demonstratedon the lateral side of the lateral femoral condyle whichcoincided with the site of the point of tenderness (Fig. 1). Itwas seen retrospectively in MRI. The intensity of the mass

165S. Kato et al. / The Knee 14 (2007) 164–166

was low on T1-weighted sequences and high on T2-weighted sequences (Fig. 2).

Arthroscopy was performed to investigate the mass andthe discoid meniscus. Inspection of the lateral joint space didnot show any tear of the discoid meniscus. Inspection of thelateral recess showed a soft tissue mass beneath the synovialmembrane of the lateral condylar side, just beneath the plicasynovialis (Fig. 3). The arthroscope was removed and a 3-cmincision was made directly over the lateral femoral condyleinto the joint space. The mass was removed en bloc with thecovering synovial membrane. The tumor had a red aspect,and was a roundish, soft, well limited mass measuring6×12×16 mm (Fig. 4). Microscopic findings showed ahighly vascular appearance and collars of glomus cells sur-rounding numerous vessels. The histology was a character-istic of glomus tumor of the vascular type (Fig. 5). Animmediate disappearance of the pain was observed after

Fig. 1. (A) Axial and (B) coronal CT scans with arthrography (air 50 ml andisobist 3 ml) of the right knee showed a small soft tissue mass on the lateralside of the lateral femoral condyle.

Fig. 2. Axial MRIs of the right knee after 40 ml saline injection into the jointshowed the mass of which intensity was low on (A) T1-weighted sequencesand high on (B) T2-weighted sequences.

surgery. On follow-up examination 3 years later, there wasneither pain nor functional disability, and there has been norecurrence of the tumor.

2. Discussion

The glomus tumors are characterized by the classic trio ofparoxysmal pain, acute pain on palpation, and sensitivity tocold, but sensitivity to cold was absent from this case.Tsuneyoshi et al. examined 63 glomus tumors removed from63 cases cliniopathologically. Histologically the tumorscould be divided into three varieties: the myxoid type, thevascular type, the solid type. While most of the tumors indigits were of the myxoid type, in other sites most of thetumors were of the vascular type and none of the myxoidtype [6]. The tumor in this case was of the vascular type.

Fig. 5. Photomicrograph of the tumor showed a highly vascular appearanceand collars of glomus cells surrounding numerous vessels.

Fig. 3. Arthroscopy showed the soft tissue mass beneath the plica synovialis.

166 S. Kato et al. / The Knee 14 (2007) 164–166

In this case, CT scan with arthrography was able todiagnose the small soft tissue tumor in the joint. It was alsoshowed in MRI, but it was demonstrated retrospectively. CTscan with arthrography nicely demonstrated that it waslocated on the lateral femoral condyle in the joint space. It isa useful diagnostic tool for detecting previously unidentifiedmass in joint space.

When the tumor is visible or palpable, there is a reddish orbluish discoloration of the skin, the high contact sensitivityproduces a sharp pain that radiates diffusely. Pain due totemperature variation is a sufficiently characteristic sign tosuggest the diagnosis. In ectopic and deep localizations, thediagnosis is more difficult, because symptoms are onlysubjective. In this case, the tumor was beneath the plicasynovialis in the knee joint and on the lateral side of thelateral femoral condyle. Therefore, the tumor was stimulatedby the plica synovitis or the lateral joint capsule with kneemotion and it caused pain on motion which was often

Fig. 4. The removed tumor had a red aspect, and was a round, soft, welllimited mass. (For interpretation of the references to colour in this figurelegend, the reader is referred to the web version of this article.)

observed in common internal derangements of the knee jointsuch as meniscal tear.

The differential diagnosis on both clinical and histologicbases includes hemangiopericytoma, hemangioma, angio-myoma, neurilemoma, and many other hamartomas. Knee-land was the first to report MR imaging of glomus tumor [2].Walter reported that it showed a serpiginous area of signalvoid representing high vascular flow were interspersedamong areas of high signal intensity caused by slowlyflowing blood and tumor cells on T2-weighted images,which was called “salt-and-pepper” pattern [5]. But this signwas not a characteristic of glomus tumor, and then mostlyglomus tumors are detected at not more than 1 cm indiameter, therefore it is difficult to diagnosis by onlyexamination images. Resection allows diagnosis by histo-logical examination, and to obtain the most durable andcomplete disappearance of symptoms. The rare cases of localrelapse would very probably be the consequence of anincomplete surgical resection or due to the lack of properlydiagnosing a multiple form. In our case, though the tumormight have been possible to remove by arthroscopy, toensure complete tumor removal, we made a small separateincision into the joint space and performed en bloc resectionof the tumor along with the covering synovial membrane.

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