The Knee 11 (2004) 501 – 502 www.elsevier.com/locate/knee
Case report
An unusual complication of knee arthroscopy: portal site synovial cyst Naveed Shaikh *, Khalid Abdel-Galil, Jon Compson Department of Orthopaedics, King’s College Hospital, London, UK Received 1 August 2003; received in revised form 9 October 2003; accepted 17 December 2003
Abstract We describe a previously un-reported case of a large synovial cyst developing in the portal site 10 years post knee arthroscopy. The pathology, indications and method of treatment are discussed. D 2004 Elsevier B.V. All rights reserved. Keywords: Knee arthroscopy; Synovial cyst
1. Introduction Arthroscopy of the knee is a common procedure which usually has a low complication rate. Most are minor, however, some can have serious and significant consequences. The commonest complications after knee arthroscopy include a large haemarthrosis/effusion, infection, excessive pain and delayed recovery [1]. We describe a previously un-reported case of a large extra-articular synovial cyst at the site of the lateral portal 10 years after knee arthroscopy.
2. Case report An 81-year-old retired army general presented complaining of pain in his right knee for several months. He had an arthroscopy of this knee 10 years prior to presentation, when a loose body was removed. On presentation, he had varus osteoarthritis affecting both knees, worse on the right and associated with a fixed flexion deformity. He also had a large cyst overlying the anterior end of the lateral joint line extending under the patella tendon. Plain radiographs of both knees revealed bilateral moderate patellofemoral and medial compartment osteoarthritic changes. Magnetic resonance imaging of the right knee (Fig.
* Corresponding author. Present address: 9 Oaklands Road, Totteridge, London N20 8BA, UK. Tel.: +44-7970-700-883. E-mail address:
[email protected] (N. Shaikh). 0968-0160/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2003.12.005
1) revealed a complex multi-loculate cyst measuring 6 cm in maximum dimension. This appeared to lie in Hoffa’s fat pad and extend antero-laterally and towards the anterior horn of the lateral meniscus. The lateral meniscus was shown to have a tear running from the superior to inferior articular surfaces. Degeneration of the medial meniscus was also noted but no tears were demonstrated. All knee ligaments were shown to be intact. In view of the patients symptoms and the MRI findings, it was decided to proceed with arthroscopy of the right knee. At surgery through an antero-medial portal, a 1 cm hole was observed in the anterolateral joint wall, above, but not connected to the lateral meniscus. Its site was consistent with the position of an anterolateral arthroscopy portal. Compression of the cyst produced extrusion of new and old haematoma. The cyst was evacuated using external compression and an arthroscopic shaver inserted from inside of the joint. Biopsies of the wall were taken and the cyst wall excised. Pressure dressings and an extension splint were applied for four weeks. Histology of the tissue revealed a fibrinous exudate, with fragments of fibrocollagenous tissue, appearances consistent with a synovial or soft tissue related cystic lesion. Six months later, the patient developed a recurrence of the cystic lesion in the right knee and underwent open exploration. The neck of the cyst was found to be at the site of the previous arthroscopy lateral portal (performed 10 years previously) with the cyst extending under the patella tendon. The cyst was excised and the capsule and retinaculum repaired. The knee had a full range of movement after the procedure apart from a mild fixed flexion deformity.
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Fig. 1. MRI of knee showing synovial cyst.
Histology of the tissue removed at this procedure revealed a benign fibrous synovial cyst showing mild chronic inflammation of the wall. Subsequently, the patient made a good recovery and no recurrence of the cyst was found at follow up a year later.
3. Discussion Complications following arthroscopy of the knee include haemarthrosis, infection, thromboembolic disease, instrument failure, ligament injuries, complex regional pain syndrome, fracture and neurological injuries. These are more likely to occur with more complex procedures such as meniscal repair, synovectomy and cruciate ligament reconstruction [1]. Despite an extensive search of the literature, we could not find any previous reports of a symptomatic extraarticular synovial cyst formation from a knee arthroscopy portal site even though this complication is well recognised after shoulder arthroscopy. The differential diagnosis of a synovial cyst can include a ganglion, meniscal cyst, pigmented villonodular synovitis, parameniscal cyst, synovial sarcoma, malignant fibrous histioma and lipoma. Most of these lesions have characteristic MRI appearances, which compliment the histology results [2].
The commonest type of synovial cyst occurs in the region of the popliteal fossa (Baker’s cysts). Tschirch et al. [3] have concluded in their MRI study of 102 asymptomatic knees that synovial cysts of the popliteal space can be found in one fifth of cases. An arthritic knee with recurrent effusions is the probable mechanism by which popliteal cysts form, but in this case, because of the arthroscopy portal, the cyst formed anteriorly. Asymptomatic cysts do not need excision. Synovial cysts can produce discomfort and limitation in joint movement [4], lesions in the viscinity of the proximal tibiofibular joint can exert pressure on the common peroneal nerve causing neurological deficits [5]. In the presence of symptoms, if there is no suspected meniscal or osteochondral disease therapeutic options include puncture and infiltration with glucocorticoids [5], arthroscopy [4] and arthrotomy. It is important to stress that unusual swellings of the knee should be investigated by MRI scan first, and apply caution about operating until malignant disease has been excluded. Arthroscopy is highly recommended because it enables us to obtain biopsies and, therefore provide accurate diagnosis, reduce damage to important structures and use multiple portals for extraction. If recurrence is suspected, another arthroscopy for re-evaluation with treatment can be combined [2]. At the time of recurrence, we felt that a better result would be achieved with open exploration and repair as most of the lesion was extra-articular. Our case report highlights the first reported case of a synovial cyst originating from a knee arthroscopy portal site and demonstrates a successful method of treatment. References [1] Allum R. Complications of arthroscopy of the knee. J Bone Joint Surg 2002;84-B:937 – 45. [2] Francesco F, Rizzello G, Maffei MV, Papalia R, Penaro V. Arthroscopic ganglion cyst excision in the anterolateral aspect of the knee. Arthroscopy April 2003;19(4):P1 – 4. [3] Tschirch FT, Schmid MR, Pfirrmann CW, Romero J, Hudler J, Zanetti M. Prevalence and size of meniscal cysts, ganglion cysts, synovial of the popliteal space, fluid filled bursae, and other fluid filled collections in asymptomatic knees on MR imaging. Am J Roetgenol May 2003;180(5):1431 – 6. [4] Drain O, Vialle R, Cordert X. Synovial cyst of the intercondylar fossa of the knee: three symtomatic cases and a review of the literature. Rev Chir Orthop Reparatrize Appar Mot April 2002;88(2):182 – 7. [5] Pagnoux C, Lhotellier C, Marek JJ, Ballard M, Clazerain P, Ziza JM. Synovial cysts of the proximal tibiofibular joint:three case reports. Joint Bone Spine May 2002;69(3):331 – 3.
