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Mucoid Degeneration and Cysts of the Meniscus
Abstract
Mucoid degeneration (MD) of the meniscus can appear in one of the two pathological forms: stromal MD and cystic parameniscal degeneration. Proposed etiologic factors are endogenous and exogenous trauma, endothelial inclusions in the cartilage during its development, chronic infection with hemorrhage and intraparanchymal hemorrhage, and mechanical stresses. Medial involvement is more frequent and is usually confined to the body of the meniscus. However, lateral involvement may appear as cystic swelling. When the menisci affected by MD are torn, the diagnosis may be delayed due to the lack of history of trauma and to relatively less severe symptoms. Cystic mass is most prominent at 45° of flexion and disappears in full flexion and full extension. External rotation of the leg at 45° of flexion is further helpful for diagnosis. The recent treatment strategy is arthroscopic meniscectomy and marsupialization of the cyst.
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This article describes modified physical examination maneuvers for diagnosing lateral meniscal cysts. The typical presentation of lateral meniscal cysts usually makes their clinical diagnosis simple, but a wide variation in size may sometimes lead to misdiagnosis. We evaluated the effect of leg rotations on the cystic swelling at 45 degrees of knee flexion. Eleven consecutive patients with positive Pisani's sign were evaluated prospectively. Lateral mid-third joint-line swelling was most prominent at 30-45 degrees of knee flexion. With the knee held at 45 degrees of flexion, the prominence was also inspected during internal and external rotation of the leg. The masses became noticeably more prominent with external rotation, and completely disappeared with internal rotation. With external rotation of the leg, even doubtful lateral meniscal cysts became apparent. Disappearance of the cystic mass with internal rotation further confirms the diagnosis.
Meniscal and ganglion cysts frequently present as palpable masses of the knee but occur at different locations than do popliteal cysts. Meniscal cysts also may be discovered incidentally on studies performed for suspected internal derangement. Sixteen cystic lesions of the knee were evaluated with MR, including 11 meniscal cysts and five ganglion cysts. Scans were performed at 1.5 T by using a transmit/receive extremity coil or a receive-only surface coil. Standard spin-echo imaging, including at least one long-TR/asymmetric-TE sequence, was performed in all cases. In six patients, gradient-echo, reduced flip-angle sequences also were done. All meniscal cysts (but none of the ganglion cysts) were associated with horizontal meniscal tears. Cysts were visualized best on the long-TR/TE images; meniscal tears were seen best on the short-TR/TE and long-TR/short-TE images. Meniscal tears and cysts were also seen well on the fast-scanning sequences. Septations were noted in four meniscal cysts and in four ganglion cysts on the long-TR/TE images. Long-TR/TE images were also useful in showing the relationship between the cyst and joint capsule in three of the ganglion cysts. MR imaging is an effective, noninvasive method for evaluating cystic lesions of the knee. Meniscal cysts are always associated with underlying horizontal meniscal tears, which can be detected with MR. Ganglion cysts are not associated with meniscal tears, but may have connections to the joint capsule, which can be detected with MR.
The purpose of this study is to describe MR imaging features of an unusual type of meniscal cyst arising from tears of the posterior horn of the medial meniscus in 10 patients.
Retrospective review of MR examinations of the knee was performed of 10 patients (nine men, one woman; mean age, 39 years) in whom evidence of a meniscal tear and a cyst-like structure around the posterior cruciate ligament (PCL) was seen.
An oval mass with low signal intensity on T1-weighted MR images and increased signal intensity on T2-weighted MR images posterior to the PCL, simulating a PCL ganglion cyst, was seen in all 10 patients. A tear of the posterior horn of the medial meniscus was also seen in all patients. The sites of communication between the cyst and meniscal tear were observed in sagittal MR images in eight patients. Septation within the cyst and associated joint effusion were seen in eight and four patients, respectively. Arthroscopy in eight patients and transmeniscal needle drainage in the other two patients confirmed both the meniscal tear and the pericruciate meniscal cyst.
Pericruciate meniscal cysts cause fluid collections posterior to the PCL, simulating a PCL ganglion cyst. Careful analysis of the posterior horn of the medial meniscus should be performed when a cyst-like structure is seen adjacent to the PCL.
OBJECTIVE. The purpose of this study was to determine the incidence of medial versus lateral meniscal cysts as seen on MR imaging.
MATERIALS AND METHODS. A total of 2572 knee MR imaging reports were retrospectively reviewed for the presence of meniscal tears and cysts. Two musculoskeletal radiologists reviewed all images with reported cysts. The type and location of meniscal tear and the presence and location of meniscal cysts were recorded.
RESULTS. A total of 1402 meniscal tears were reported in 2572 MR examinations (922 [66%] of 1402 in the medial compartment; 480 [34%] of 1402 in the lateral compartment). Meniscal cysts were present in 109 (4%) of 2572 knees. Of the 109 cysts, 72 (66%) were in the medial compartment, and 37 (34%) were in the lateral compartment. Meniscal cysts were found in association with 72 (7.8%) of the 922 medial meniscal tears and 37 (7.7%) of the 480 lateral meniscal tears. Meniscal cysts showed direct contact with an adjacent meniscal tear in 107 (98%) of 109 cases, with the tear showing a horizontal component in 96 (90%) of 107 cases.
CONCLUSION. Meniscal cysts occur almost twice as often in the medial compartment as in the lateral compartment. Medial and lateral tears occur with the same frequency. These findings, when viewed in the context of the historical literature on meniscal cysts, suggest that MR imaging detects a greater number of medial meniscal cysts than physical examination or arthroscopy, and that MR imaging can have an important impact on surgical treatment of patients.
IN 1938, while on Dr. Arthur Krida's Orthopedic Service at Bellevue Hospital, I removed a cyst of the medial meniscus. It was observed at that time that the hemispherical cystic mass disappeared into the knee joint on acute flexion and reappeared on extension of the knee, reaching its maximum dimensions at a point 25 to 30 degrees short of complete extension.
In 1943 I presented before the Canal Zone's Isthmian Medical Society a series of twelve cysts of the knee cartilages, both internal and external. The pathognomonic "disappearing sign" was described as a common finding in each of the patients operated on by Lieutenant Colonel Marcus Schwartz and me.
During the past three years eighteen more cysts of the medial and lateral menisci have been diagnosed and fifteen of them excised. In each of this last series the physical sign was present, viz., disappearance on acute flexion and reappearance on
Biochemical changes in the articular cartilage of the knees of mature dogs, one with natural and four with surgically induced osteoarthritis, have been investigated. The four dogs were killed three, six, nine and forty-eight weeks after division of the right anterior cruciate ligament, the left knees serving as controls. The cartilage of the joints operated on was thicker and more hydrated than the control cartilage; the proteoglycans were more easily extracted and had higher galactosamine/glucosamine molar ratios. The proportion of proteoglycans firmly associated with collagen, and hence not extractable, diminished before fibrillation was demonstrable by indian ink staining of the surface. These biochemical changes were present throughout the entire cartilage of the joints operated on of the dogs killed more than three weeks later, and of the dog with natural osteoarthritis. The results suggest that in response to altered mechanical stresses the chondrocytes synthesise proteoglycans that contain more chondroitin sulphate relative to keratin sulphate than normally, as in immature articular cartilage.
The semilunar cartilages of the knee of six cases showing various degrees of mucoid degeneration with cyst formation were studied with the light microscope. Three cases were selected for electron microscopic observation which revealed that some of the cystic spaces filled with mucoid material were lined by synovial cells. Masses of mucinous, alcian bluc positive material (acid mucopolysaccharides) were observed also among degenerated and intact bundles of collagen. It is concluded that the accumulation of acid mucopolysaccharides in meniscial cysts is at least in part a product of secretion of synovial cells. This observation explains the high incidence of recurrence of meniscial cysts after incomplete surgical excision and supports the concept that it is an active rather than a degenerative process.
Twenty-two patients with cysts of the lateral meniscus have been treated by operation. A modified operative procedure is described whereby the meniscus is inspected for a concomitant tear. A tear of the meniscus was found in ten patients and these were treated by meniscectomy. The remaining twelve cases were treated by excision of the cyst only. The rehabilitation period was considerably less in these patients. Recurrence of the cyst did not occur. The rationale for local excision is based on the similarity between the cyst of a meniscus and a simple ganglion, and also on the desirability of preserving the meniscus.
Thirty-six patients underwent arthroscopic cystectomy and partial meniscectomy for a lateral meniscal cyst. In two other patients, an open cystectomy was performed following a diagnostic arthroscopy. The patients were reviewed at an average of 39 months (range 8-82) after the operation, and recurrence was found in four cases. Five patients, all keen sportsmen, were dissatisfied with the operation. Four patients, with arthroscopic signs of early degenerative arthritis, were still experiencing some pain, but were able to lead a normal working and social life. Arthroscopy is safe, giving low morbidity and recurrence. In the cases treated by arthroscopy, a horizontal meniscal tear was always found. The question whether this tear and the resulting meniscal changes are traumatic or degenerative in origin still remains; and, to some extent, neither hypothesis can be readily discarded. This study supports the use of arthroscopy alone in the treatment of lateral meniscal cysts.
Meniscal cysts are cysts that occur as a direct extension, or within the substance of the meniscus. The incidence varies in reports from 1% to 20% and are much more common laterally. They usually present as joint-line pain, swelling, or both in young adult men, and are often associated with meniscal tears. The exact etiology of meniscal cysts is unknown. A myxoid degenerative process is identified histologically. There is often a history of precedent trauma. Diagnosis is often suspected clinically and can be confirmed by arthrogram, CT, or MRI when necessary. Conservative treatment in the patient with few symptoms is recommended. Should the cyst become significantly symptomatic, it is necessary to treat the meniscal pathology to prevent a cyst recurrence. At the present time it is our recommendation that this be done by arthroscopically resecting the meniscus back to normal meniscus and either aspirating and injecting the cyst with steroid or local cyst excision if the aspiration and injection fails. If no meniscal tear is documented at arthroscopy, exploration and excision of the cyst are recommended.
A retrospective clinical study evaluated the results of arthroscopic management of cysts of the menisci. From 1979 to 1984, 24 patients with a diagnosis of meniscal cysts associated with tears of the semilunar cartilage were treated with partial meniscectomy and cyst decompression. The mean age was 29.9 years (range, 14-52 years). Each patient had tenderness over the joint line with a palpable mass. There were 25 cases of meniscal cysts, with one patient having a bilateral cyst. Twenty-two cysts involved the lateral meniscus, and three cysts were on the medial side of the knee. The follow-up period ranged from 16 to 48 months (mean, 33.5 months). All patients had a meniscal tear; most tears were either horizontal or transverse, with or without flap formation. The pathology was in the middle or anterior one-third of the meniscus. The arthroscopic surgery consisted of partial excision of the meniscal tear, leaving a peripheral rim at times, coupled with aspiration of the cyst material or manipulation of its contents into the joint cavity. No cyst recurred, and in every patient except one, preoperative symptoms disappeared. All patients but one were satisfied with the results. Two patients had a second arthroscopy, and no evidence of instability of the peripheral rim was found.
The meniscus is characterized at the light microscopic and ultrastructural levels by thick collagen fibers that are predominantly circumferential in orientation. The extracellular matrix of the meniscus is composed mainly of collagen, with smaller quantities of proteoglycans, matrix glycoproteins, and elastin. The collagen is predominantly Type I, with smaller quantities of Types II, III, and V. The proteoglycans are mainly large, aggregating proteoglycans with chondroitin sulfate as their dominant glycosaminoglycan. A small proportion of small dermatan sulfate proteoglycans is probably present. The matrix glycoproteins include the link proteins, the 116-k protein, and a group of adhesive or potentially adhesive proteins that includes Type VI collagen (here classified as a glycoprotein with a collagenous domain), fibronectin, and thrombospondin. The fibrochondrocytes of the meniscus appear to have considerable potential to respond to growth and other modulating factors in the repair or regeneration of the tissue.
A retrospective analysis was performed on 32 knees in 31 patients with the diagnosis of cyst of the lateral meniscus. Average follow-up was 41 months, with a range of 16-72 months. Surgical and histological examination demonstrated pathology varying from large meniscal tears with minimal cyst formation to large cysts with no demonstrable meniscal tear. Two theories of etiology emerged: (a) The tear begins in the meniscus and spreads through the periphery. (b) The lesion begins as a compression injury to the vascular periphery and spreads centrally, producing a meniscus tear, or peripherally, producing a cyst, or both. In our series, 20 patients managed by arthroscopic partial meniscectomy and open cystectomy had 80% excellent-good results versus 50% excellent-good results in 12 patients treated with arthroscopy and partial meniscectomy without extraarticular cystectomy. We recommend the following treatment: arthroscopy with a diligent search for a lateral meniscal tear, especially peripherally. If none is found, proceed to extraarticular cystectomy. If a tear is found, remove all unstable meniscal fragments, leaving a rim, if possible, especially adjacent to the popliteus recess, and then proceed to open cystectomy.
Twelve patients with cystic degeneration of the lateral meniscus were submitted to magnetic resonance and arthroscopy. This study showed that mixoid degeneration is produced initially within the meniscal substance and subsequently progresses towards and may rupture through the outer margin, so producing the clinically detectable cyst on the outer margin of the joint. In the light of the information obtained from magnetic resonance and subsequent surgical verification, existing hypotheses regarding the pathogenesis and evolution of the lesion have been re-examined.
Menisci from 12 autopsies and above-knee amputations were imaged with magnetic resonance (MR) at 1.5 T and then sectioned for gross and histologic examination. A histologic staging system was developed and showed a one-to-one correlation with corresponding grades of MR signal intensities. Histologic stages 1 and 2 represented a continuum of degeneration culminating in stage 3 fibrocartilaginous tears, seen most frequently in posterior-horn segments of the medial meniscus. Correlation of histologic stages with MR signal intensity allows for an improved diagnostic reading of MR images.
Before surgery, 277 menisci in 144 knees were examined with magnetic resonance (MR) imaging. They were then examined directly with arthroscopy or arthrotomy. Menisci were graded on a scale of 1-3 according to the character of the intrameniscal MR imaging signal. At surgery, 137 of 154 (89%) menisci exhibiting only grade 1 or grade 2 signal were found to be normal. One hundred sixteen of 123 (94%) menisci exhibiting intrameniscal signal communicating with a meniscal articular surface (grade 3 signal) had tears. If only a grade 3 signal is considered consistent with meniscal tears, then MR findings and surgical findings agreed in 91.3% of menisci. MR imaging can separate surgically significant from nonsignificant meniscal lesions and is useful in the noninvasive preoperative screening of suspected meniscal tears.
This study presents seven cases of lateral meniscal cysts treated arthroscopically. All were noted to have meniscal lesions at the time of surgery; there were five flap tears and two radial tears. Partial arthroscopic meniscectomy was performed and the contents of the cysts were manipulated into the joint in six of seven cases. One patient underwent open cyst excision in addition to partial arthroscopic meniscectomy. Followup ranged from 18 months to 4 years with an average of 28 months. There were no cyst recurrences. The pathologic basis of the meniscal cyst is controversial, but recent work suggests the etiology is infiltration of joint fluid through micro and macro tears in the meniscus. Partial meniscectomy retains valuable meniscal function while minimizing the likelihood of cyst reformation. We found arthroscopic partial meniscectomy with manipulation of the contents of the cyst into the joint to be a successful alternative to complete open meniscectomy.
A review is presented of 500 cases of cystic menisci diagnosed clinically. The distribution by age, sex, side, and site is analysed as is the mode of presentation, history, and type of trauma, as well as locking.Operative findings in 299 patients are discussed, undamaged menisci being found in 50 per cent.With a history of trauma (37 per cent) the meniscus was found to be damaged in 59 per cent, without it the incidence was 45 per cent.
The present state of knowledge about cysts of the menisci is summarized and a report of sixteen new cases in six of which arthrography demonstrated a portion of the cystic area is presented.
Horizontal cleavages and lateral cysts were examined in a series of 70 menisci. The horizontal cleavage (HC) is the most frequent form of tear, occurring most often in the middle third of the lateral meniscus. Horizontal cleavages which reach the base of the meniscus triangle connect with parameniscal cysts. Extension of the horizontal cleavage into the parameniscal region seems to be, therefore, the cause of cyst formation.
Systematic macroscopic and microscopic measurements of the tibial surface of 70 menisci helped to reveal associated minimal dysplastic lesions. The normal meniscus is divided into upper and lower areas by the middle perforating bundle. Considering its high frequency, a minimal myxoid degeneration in the center of the meniscus is normal. Classic myxoid degeneration may be divided into 2 types. Type A or parameniscal cystic degeneration, and Type B or intrameniscal myxoid degeneration. The intrameniscal myxoid degeneration is a nonspecific reaction to injury. Parameniscal mucoid degeneration constitutes the substrate of lateral meniscal cysts.
It is likely that meniscal cysts of the knee are a complication of meniscal tears which extend to the capsular attachment. They are reported as occurring three times more commonly on the lateral than the medial side. We reviewed 50 cases of meniscal cysts diagnosed on magnetic resonance imaging in patients with suspected internal derangement of the knee. Twenty-eight cysts involved the medial and 22 the lateral meniscus. The most common sites were the posterior third of the medial meniscus and the mid-third of the lateral meniscus. Fifteen cysts were suspected clinically, five on the medial side and 10 on the lateral side. Small cysts were only clinically predicted on the lateral side. We conclude that menial cysts are more common than previously thought and are more difficult than lateral cysts to detect clinically.
Historically meniscal cysts have been treated with either an open total menisectomy, isolated cyst excision, or a combination of the two procedures. The advent of arthroscopic techniques has led to innovative treatment options for meniscal cyst management. A review of meniscal cysts and the results of arthroscopic treatment form the basis of this study. From 1986 to 1991, 18 patients with meniscal cysts were treated by arthroscopic cyst decompression. Thirteen men and five women comprised the study group and had an average age of 28 years. The follow-up period ranged from 6 to 60 months (average 26). Eight of the cysts were medial and 10 were lateral. A horizontal cleavage tear was noted in all cases, and 15 partial and three subtotal menisectomies were performed in conjunction with an intraarticular cyst decompression. There have been no recurrences to date, and all patients returned to their previous level of activity. Parameniscal cysts may result from synovial fluid tracking through a horizontal cleavage tear. Successful treatment of the meniscal cyst must include appropriate management of the torn meniscus, which can be entirely arthroscopic, consisting of a partial or subtotal meniscectomy, identification of the cyst opening, and cyst decompression.
We have treated 69 patients with 72 cystic lateral menisci by arthroscopic surgery. Meniscal tears were observed in all cases, and 69 of these had a horizontal cleavage component. Three types of tear were identified and may be progressive. Treatment was by arthroscopic resection of the meniscal tear, and decompression of the cyst through the substance of the meniscus. After a mean follow-up of 34 months the results were good or excellent in 64 knees (89%) and there were few complications. We recommend this technique as the treatment of choice for cysts of the lateral meniscus.
We report the clinical and arthroscopic findings in 20 cases of medial meniscal cyst with a mean follow-up of 20 months. These were studied prospectively from a series of 7435 knee arthroscopies in which there were 1246 stable non-arthritic knees with medial meniscal tears. The diagnosis on referral was incorrect in seven, and incomplete in seven. There was coexistent meniscal injury in 17 (85%), but in the other three no tear was visible at arthroscopy. Ten knees had additional intra-articular abnormalities. Treatment of the cyst was by open resection in 12 and arthroscopic evaluation at meniscectomy in seven. In one case the cyst resolved after arthroscopic partial meniscectomy alone. Meniscal tears were treated by arthroscopic partial medial meniscectomy. Medial meniscal cysts are an important but under-diagnosed cause of knee pain and are frequently related to arthroscopically diagnosable and treatable meniscal pathology. Treatment should be directed towards both the meniscus and the cyst, which may require open surgery.
Cystic degeneration of the meniscus is not uncommon. Recent reports suggest that most (or all) meniscal cysts are associated with a meniscal tear, and that the treatment of choice is arthroscopic partial meniscectomy with cyst decompression. This report describes a case of a symptomatic lateral meniscal cyst that was suspected clinically and confirmed by magnetic resonance imaging, but was not associated with a meniscal tear at arthroscopy. Open cyst extirpation and peripheral meniscal repair were performed to maximize preservation of meniscal tissue. A clinical algorithm is presented for management of meniscal cysts.
The purpose of this study was to determine the incidence of medial versus lateral meniscal cysts as seen on MR imaging.
A total of 2572 knee MR imaging reports were retrospectively reviewed for the presence of meniscal tears and cysts. Two musculoskeletal radiologists reviewed all images with reported cysts. The type and location of meniscal tear and the presence and location of meniscal cysts were recorded.
A total of 1402 meniscal tears were reported in 2572 MR examinations (922 [66%] of 1402 in the medial compartment; 480 [34%] of 1402 in the lateral compartment). Meniscal cysts were present in 109 (4%) of 2572 knees. Of the 109 cysts, 72 (66%) were in the medial compartment, and 37 (34%) were in the lateral compartment. Meniscal cysts were found in association with 72 (7.8%) of the 922 medial meniscal tears and 37 (7.7%) of the 480 lateral meniscal tears. Meniscal cysts showed direct contact with an adjacent meniscal tear in 107 (98%) of 109 cases, with the tear showing a horizontal component in 96 (90%) of 107 cases.
Meniscal cysts occur almost twice as often in the medial compartment as in the lateral compartment. Medial and lateral tears occur with the same frequency. These findings, when viewed in the context of the historical literature on meniscal cysts, suggest that MR imaging detects a greater number of medial meniscal cysts than physical examination or arthroscopy, and that MR imaging can have an important impact on surgical treatment of patients.
To analyze the extension of medial and lateral meniscal cysts relative to the capuloligamentous planes of the knee.
The MR images of 32 patients with meniscal cysts were reviewed. The location and extension of the meniscal cysts with reference to the capsule and ligaments were recorded.
Most medial meniscal cysts were located posteromedially. Posteromedial meniscal cysts usually penetrated the capsule and were located between layer I and the fused layers II+III. From this site some extended anteriorly and then became located superficial to the superficial MCL. The location of lateral meniscal cysts was more varied. Anteriorly the cysts were located deep to the iliotibial band, whereas posterolateral cysts were located deep to the lateral collateral ligament.
Although the site of capsular penetration of meniscal cysts is determined by the location of meniscal tears, the possible pathways of extension appear to be determined by the capsuloligamentous planes of the knee.
Meniscal cysts are uncommon cystic lesions around the knee, and pericruciate meniscal cysts are the most rare types. Here we present an unusual case of a pericruciate meniscal cyst located laterally to the anterior cruciate ligament (ACL), causing erosion of the adjacent tibial plateau.
Mucoid degeneration (MD) of the meniscus has received little attention. The pathology deserves special interest as it may lead to loss of the meniscus even in very young individuals. The cause of MD and the clinical features of meniscal tears due to that pathology have not been understood. This study analyzed the age profile and the role of trauma in patients with torn menisci with MD, examined meniscal tear patterns and clinical features, and investigated the role of bacterial infection in causing MD. Meniscal samples obtained from 27 consecutive patients during arthroscopic resection of torn menisci considered to be due to MD (typical yellow color) underwent pathological investigation. The samples were scored according to the light microscopic criteria of Copenhaver; 24 menisci (23 patients) with stage 2-3 MD comprised the study group. Magnetic resonance imaging obtained in 11 patients typically revealed increased intrasubstance signal intensity that extended to at least one of the meniscal surfaces. Pieces of resected meniscal tissue were also subject to PCR investigation to search for presence of bacteria. Of the 24 knees 21 (87%) had no history of trauma. Mean Tegner activity level was 4 (1 and 7). Mean duration of symptoms was 11.6 months (1-36). Pain was the most frequent symptom ( n=22). Joint line tenderness and McMurray's test (pain and/or clicking) were present in 22 and 16 knees, respectively. Medial meniscus was affected in 16 and lateral meniscus in 8. Meniscal cyst and incomplete discoid meniscus was present in 5 and 2 of the lateral menisci. All of the torn menisci were degenerated and yellow in color. The most common tear patterns were radial and/or flap, and longitudinal-horizontal tears. PCR study revealed no bacteria. Mucoid degeneration of the meniscus does not seem to be related to the aging process. Clinical findings of torn such menisci are insidious compared to traumatic tears. Lack of history of trauma may delay the diagnosis. Bacterial infection has no role in the cause.
This review presents a comprehensive illustrated overview of the wide variety of cystic lesions around the knee. The aetiology, clinical presentation, MRI appearances and differential diagnosis are discussed. Bursae include those related to the patella as well as pes anserine, tibial collateral ligament, semimembranosus-tibial collateral ligament, iliotibial and fibular collateral ligament-biceps femoris. The anatomical extension, imaging features and clinical significance of meniscal cysts are illustrated. Review of ganglia includes intra-articular, extra-articular, intraosseous and periosteal ganglia, highlighting imaging findings and differential diagnoses. The relationship between proximal tibiofibular joint cysts and intraneural peroneal nerve ganglia is discussed. Intraosseous cystic lesions, including insertional and degenerative cysts, as well as lesions mimicking cysts of the knee are described and illustrated. Knowledge of the location, characteristic appearance and distinguishing features of cystic masses around the knee as well as potential imaging pitfalls such as normal anatomical recesses and atypical cyst contents on MR imaging aids in allowing a specific diagnosis to be made. This will prevent unnecessary additional investigations and determine whether intra-articular surgery or conservative management is appropriate.
A case of intra-articular pericruciate type of meniscal cyst from anterior horn of lateral meniscus without associated meniscal tear is reported with review of literature. To our knowledge such association has not been reported earlier.
Meniscal cysts begin with extrusion of synovial fluid through a tear of the meniscus, enlarging probably as a result of a one-way valve effect of the tear flap. We describe a technique of arthroscopic internal marsupialization of meniscal cysts with or without meniscectomy. A 5 mm channel was created in the capsule adjacent to the cyst arthroscopically for decompression of the cyst into the joint, thus equalising pressures between the cystic and intra-articular compartments. Only unstable meniscal tears were debrided down to a stable rim while intact meniscii or stable tears were left alone. Eight patients with MRI confirmed atraumatic medial or lateral meniscal cysts underwent surgery. At a mean follow-up of 39.1 months (12-94 months, S.D. 26.4), Tegner scores averaged 5.1 (3-8, S.D. 2.1) and Lysholm scores averaged 94.4 (85-100, S.D. 5.4). No cyst recurred. Arthroscopic internal marsupialization effectively decompresses meniscal cysts and prevents their recurrence, while preserving meniscal tissue and minimising arthrosis of the knee joint.
Cystic lesions around the knee comprise a diverse group of entities, ranging from benign cysts to complications of underlying diseases such as infection, arthritis, and malignancy. Their diverse causes result in varied prognoses and therapeutic options. Although the presentation of cystic masses may be similar, their management may differ, thus highlighting the importance of appropriate categorization. MR aids in the characterization of lesions by first localizing them, and then defining their relationship with adjacent structures and identifying any additional abnormalities. For the purpose of this article, the authors limit the scope of their discussion to benign cysts, ganglia, and bursae about the knee.
Cystic lesions around the knee are a diverse group of entities, frequently encountered during routine MRI of the knee. These lesions range from benign cysts to complications of underlying diseases such as infection, arthritis, and malignancy. MRI is the technique of choice in characterizing lesions around the knee: to confirm the cystic nature of the lesion, to evaluate the anatomical relationship to the joint and surrounding tissues, and to identify associated intra-articular disorders. We will discuss the etiology, clinical presentation, MRI findings, and differential diagnosis of various cystic lesions around the knee including meniscal and popliteal (Baker's) cysts, intra-articular and extra-articular ganglia, intra-osseous cysts at the insertion of the cruciate ligaments and meniscotibial attachments, proximal tibiofibular joint cysts, degenerative cystic lesions (subchondral cyst), cystic lesions arising from the bursae (pes anserine, prepatellar, superficial and deep infrapatellar, iliotibial, tibial collateral ligament, and suprapatellar), and lesions that may mimic cysts around the knee including normal anatomical recesses. Clinicians must be aware about the MRI features and the differential diagnosis of cystic lesions around the knee to avoid misdiagnosis.
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