Case Report
Medial Meniscus Anterior Horn Cyst: Arthroscopic Decompression ¨ g˘u¨t, M.D., Hayrettin Kesmezacar, M.D., Rıfat Erginer, M.D., I˙stemi Yu¨cel, M.D., Tahir O and Muharrem Babacan, M.D.
Abstract: Meniscus cysts are mostly seen with meniscus tears, and arthroscopic decompression of cysts is gaining great importance in their treatment. In this study, we present a medial meniscus anterior horn cyst without an accompanying tear in the meniscus. A 33-year-old male patient was seen with pain and a palpable mass in his right knee. He complained that the severity of the pain had increased over the previous year. After the clinical and radiologic examinations, a painless, fixed soft tissue mass averaging 4 ⫻ 5 cm was located just medial to tuberositas tibia. The cyst was decompressed arthroscopically. In the 18th month of follow up, the mass had totally disappeared and the patient had no pain. Medial meniscus cysts are seen nine times fewer than lateral meniscus cysts. They are mostly accompanied with meniscal tears. Total meniscectomy with arthrotomy, isolated cyst excision, cyst excision, and partial meniscectomy with arthrotomy and arthroscopic partial meniscectomy with cyst decompression are treatment modalities. Arthroscopic meniscal cyst decompression is an important treatment choice and should always be taken into consideration with low morbidity, short recovery period, low recurrrence rate, preservation of range of motion, and permission for early mobilization and rehabilitation of the joint. Key Words: Medial meniscus—Anterior horn cyst—Arthroscopy—Decompression.
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edial meniscus cysts, especially in the anterior horn, are quite rarely seen, and there are very limited known studies in this subject.1 These cysts are mostly seen with meniscus tears. In the past, cyst excision and total meniscectomy with arthrotomy was the choice of treatment, but with the development of arthroscopic techniques, cyst decompression is being accepted as a routine procedure.1,2 METHODS AND RESULTS In October 2000, a 33-year-old male patient was seen with long-duration pain and a palpable mass in
From the Department of Orthopaedics and Traumatology, ˙Istanbul University, Cerrahpas¸a Faculty of Medicine, I˙stanbul, Turkey. ¨ g˘ u¨ t, Address correspondence and reprint requests to Tahir O M.D., ˙Istanbul University, Cerrahpas¸a Faculty of Medicine, Department of Orthopaedics and Traumatology, ˙Istanbul, Turkey. E-mail:
[email protected] or
[email protected] © 2004 by the Arthroscopy Association of North America 0749-8063/04/2006-3756$30.00/0 doi:10.1016/j.arthro.2004.04.006
his right knee. He complained that the severity of the pain had increased over the previous year, and he was working in a textile company standing all day long and handling heavy objects. An increase of the volume of the mass was another complaint he reported. After the clinical and radiologic examinations, a 4 ⫻ 5-cm painless, fixed soft tissue mass located just medial to the tuberositas tibia, related to the knee joint cavity, was diagnosed. There was minimal effusion in the joint cavity, the right thigh muscles were 1 cm atrophic compared with the left side, and McMurray test was positive. There was no neurologic or circulatory problem in his right lower extremity. The radiologic examination was performed and, there was a grade III tear of the posterior horn of medial meniscus, and a meniscal cyst extending to the anterior border of the knee joint was detected on magnetic resonance imaging of the right knee (Fig 1). Right knee arthroscopy was performed under pneumatic tourniquet (Fig 2). Methylene blue was injected through the anterior-distal wall into the cyst extra-
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 20, No 6 (July-August, Suppl 1), 2004: pp 9-12
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FIGURE 1. A 33-year-old male patient with a medial meniscus anterior horn cyst. Preoperative magnetic resonance image shows medial meniscus anterior horn cyst.
articularly and arthroscopically, an intra-articular relation between the cyst and medial meniscus was found. There was no tear in the medial meniscus and only grade I degeneration at the anterior horn. The wall of the cyst related to the anterior horn of the medial meniscus was detected and excised with a punch. The content of the cyst drained into the joint
FIGURE 3.
Histologic photomicrograph of the removed cyst.
cavity and the mass disappeared. Histologic examination of the removed cyst showed connective tissue with myxoid degeneration and a hyalinized fibrous wall (Fig 3). Rehabilitation of the patient was started immediately after the operation. In April 2002, in the 18th month of follow up, the patient was back to work with no knee pain and he was very satisfied with the operation. Physical examination of the left knee demonstrated a range of motion from 0° extension to 130° flexion and no mass was palpated. Radiographic examination was normal and magnetic resonance imaging of the right knee revealed no recurrence of the mass (Fig 4).
DISCUSSION
FIGURE 2. Perioperative photograph of the involved knee, before arthroscopic decompression.
According to Passler et al.,3 the chance of observing meniscus cysts during knee arthroscopies is 1.4% (medial 12.5%, lateral 87.5%). Medial meniscus cysts are seen less frequently than the lateral meniscus cysts.4,5 Maffulli et al.2 reported that meniscus cysts are seen three to 10 times more common on the lateral side. Studies report that the ratio of cysts seen on the medial side to all meniscal cysts are between 0% and 12.5%.2,3,5-8 The highest ratio is reported by Ryu and Ting9 as 44.4%. In reported series that include medial meniscal cyst, the number of cases is very low. Mills et al.,1 having one of the largest series, presented 20 medial meniscal cysts treated arthroscopically. In other few studies, the number of cases varies between 1 and 13.1 Meniscal cysts are generally associated with meniscus tears.4,5,8,10 The percentage of meniscus tears ac-
MEDIAL MENISCUS ANTERIOR HORN CYST
FIGURE 4. Magnetic resonance image of the right knee 18 months after arthroscopic decompression of the medial meniscus anterior horn cyst shows no cystic mass.
companying meniscal cysts was between 18% and 86% when arthrotomy was the choice of surgical treatment, but with the development of arthroscopic techniques, this percentage is increasing.9 Several investigators presented percentages for meniscal tears accompanying meniscal cysts as follows: Glasgow et al.,8 84%; Mills and Henderson,1 85%; Passler et al.,3 87.5%; and Parisien5 and Burk et al.,11 100%. Mafulli et al.2 found no tear in only two of 38 cases; the rest had radial tears. Keating et al.6 found horizontal cleavage or radial tears in all of his patients. Mills and Henderson1 reported most common meniscus tear type seen together with meniscal cysts as the horizontal cleavage tear. In our case, a medial meniscus anterior horn cyst was treated with arthroscopic decompression. No meniscal tear was detected in arthroscopy procedure, although preoperative magnetic resonance imaging study revealed a posterior horn tear in medial meniscus. Lateral meniscus cysts are mostly located in the midportion of the meniscus8 and usually there is a connection between the corpus and anterior horn of the meniscus.9 On the contrary, medial meniscus cysts are generally found at the posterior horn or posterior horn– corpus junction.9 However, in our case, the cyst originated from the anterior horn of the medial meniscus. In the past, Mills and Henderson1 reported only one anterior horn cyst in 20 medial meniscus cysts, and there were only two in 11 medial meniscus cysts reported by Burk et al.11
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Only cysts larger than 2 cm can be palpated.1 In one study, the sizes of the cysts were reported as between 2 ⫻ 1 cm and 4 ⫻ 6 cm.5 The cyst in our case was very large, atypically located and approximately 4 ⫻ 5 cm in size. It is known that there is no correlation between the size of the cyst and the amount of the meniscus resected.9 In two studies, radiologic examination attempting to detect bone pathology showed slight erosion at the same side tibial plateau,2 and an invasion in medial femoral condyle mimicking solitary bone lesion12 was found. Our patient had no radiographic osseous pathology resulting from the meniscus cyst, preoperatively and during the 18th month follow up. A variety of treatments has been suggested for meniscal cysts. Earlier reports recommended total open meniscectomy,2 excision of the cyst,2 or cyst decompression6 with arthroscopic partial meniscectomy, local open excision of the cyst alone,9 or partial open meniscectomy with excision of the cyst.9 The injection of cysts with steroid is another treatment modality. It has been proposed that steroid injection could damp down an inflammatory process within the meniscus and allow the cyst walls to fibrose.7 However, according to Mills and Henderson,1 the role of steroid injection in medial meniscal cyst is unknown and most likely will fail and result in shortterm relief for a few weeks. We did not use steroid after decompression and the cyst did not recur in our case. Meniscus cysts are always multiloculated.6 Mafulli et al.2 reported the macroscopic appearance of a meniscal cyst as a multiloculated mass, composed of a main cavity with multiple associated microcavities and microscopic appearance as areas with various degrees of mucoid degeneration. Mills and Henderson1 found mild nonspecific inflammation around a multilocular cavity lined with a synovial type of epithelium. Recurrence of the medial meniscus cysts are reported as 0%,1,3,5,9 7.1%,6 and 11.1%.2 In our case, after an 18-month follow up, we found no sign of recurrence. When the treatment results of meniscal cysts are being evaluated, a satisfactory outcome should be regarded as the one in which the patient regained full range of motion, was able to return to full activities without limitation, and did not experience cyst recurrence.9 In the 18th month of follow up, the clinical and radiographic examination of the patient was quite normal. The patient stated that he was very satisfied with the surgery, returned to his preoperative job, and
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had no knee pain. Physical examination of the left knee demonstrated a range of motion from 0° extension to 130° flexion and no mass was palpated. Radiographic examination was normal and magnetic resonance imaging of the right knee revealed no recurrence of the mass. Medial meniscus cysts should always be considered in patients referring with knee pain on the medial side of the joint and a palpable mass. The diagnosis is quite easy with clinical and radiologic examination, especially when magnetic resonance imaging is available. If symptoms are mild and no mechanical symptom is present, conservative treatment could be offered, including steroid injection into the cyst, but surgical treatment should always be taken into consideration because of the high association of a meniscal tear. The primary surgical procedure should be arthroscopic decompression of the cyst combined with partial meniscectomy if a meniscal tear is detected. This case report presents the rarity of medial meniscus anterior horn cysts, detection of no tear in the medial meniscus anterior horn, the cyst being very large, the understanding of an intra-articular relation of the cyst with clinical examination, and its cure only with arthroscopic decompression.
REFERENCES 1. Mills CA, Henderson IJ. Cysts of the medial meniscus. Arthroscopic diagnosis and management. J Bone Joint Surg Br 1993;75:293-298. 2. Maffulli N, Petricciuolo F, Pintore E. Lateral meniscal cyst: Arthroscopic management. Med Sci Sports Exerc 1991;23: 779-782. 3. Passler JM, Hofer HP, Peicha G, Wildburger R. Arthroscopic treatment of meniscal cysts. J Bone Joint Surg Br 1993;75: 303-304. 4. Bresler M, Olson M. Radiologic case study: Lateral meniscal cyst. Orthopedics 1990;13:667-674. 5. Parisien JS. Arthroscopic treatment of cysts of the menisci: A preliminary report. Clin Orthop 1990;257:154-158. 6. Keating JF, Muirhead A, MacMillan J, Scott PDR. Arthroscopic decompression of meniscal cysts: Report of 14 cases. J R Coll Surg Edinb 1991;36:137-138. 7. Muddu BN, Barrie JL, Morris MA. Aspiration and injection for meniscal cysts. J Bone Joint Surg Br 1992;74:627-628. 8. Glasgow NMS, Allen PW, Blakeway C. Arthroscopic treatment of cysts of the lateral meniscus. J Bone Joint Surg Br 1993;75:299-302. 9. Ryu RKN, Ting AJ. Arthroscopic treatment of meniscal cysts. Arthroscopy 1993;5:591-595. 10. Miller RH. Knee injuries. In: Canale ST, ed. Operative Orthopaedics. Ed 9. St. Louis: Mosby, 1998;1150-1152. 11. Burk DL Jr, Dalinka MK, Kanal E, et al. Meniscal and ganglion cysts of the knee: MR evaluatuion. AJR Am J Roentgenol 1988;150:331-336. 12. Mason RJ, Friedman SJ, Frassica FJ. Medial meniscal cyst of the knee simulating a solitary bone lesion. Clin Orthop 1994; 304:190-194.
