Small Medial Meniscocapsular Separations: A Potential Causeof Chronic Medial-Side Knee Pain

Iftach Hetsroni, M.D., Kaitlyn Lillemoe, B.A., and Robert G. Marx, M.D., M.Sc., F.R.C.S.C.

Purpose: To describe clinical characteristics, surgical findings, and functional outcome afterarthroscopic repair of a unique type of meniscocapsular separation. Methods: We retrospec-tively reviewed office charts, magnetic resonance imaging (MRI) scans, operative reports, andarthroscopic images of 6 patients who underwent surgery between January 2007 and May 2009,in whom a medial meniscocapsular separation measuring less than 5 mm in length was identifiedand treated. Inclusion criteria were medial-side knee pain unresponsive to nonoperative man-agement, negative MRI findings, and an isolated meniscocapsular separation injury detected onarthroscopy and repaired with 1 stitch. Patients were contacted and completed questionnairesthat included subjective International Knee Documentation Committee, Tegner, and Marxscores. Results: Of the 6 patients, 5 were female patients aged 14 to 18 years who were involvedin sports. All patients recalled an acute twisting knee injury. Symptoms were related mainly tosports and were absent or very minimal during activities of daily living. On physical examina-tion, the medial joint line was tender in all patients, whereas medial-side knee discomfort whilesquatting (i.e., baseball catcher’s position) and McMurray tests were positive only in some. Thenegative MRI scans used a 3-T magnet in 5 cases and a 1.5-T magnet in 1 case. The durationof symptoms from injury to surgery was between 6 months and 9 years in 5 cases. Onarthroscopy, all patients had a medial meniscocapsular separation measuring less than 5 mm inlength that was identified when the tip of the arthroscopic probe was inserted into the lesion. Thiswas repaired with a single all-inside stitch. The mean latest follow-up was 31 months (range, 15to 38 months). The mean subjective International Knee Documentation Committee score was 87at latest follow-up. Tegner and Marx scores showed that after surgery, 5 patients regained theirpreinjury level of activity. Conclusions: Meniscocapsular separation can involve a segment ofless than 5 mm in length, be occult on MRI, be challenging to visualize on arthroscopy, and leadto chronic medial-side knee pain. Critical evaluation with a history, physical examination, andcareful arthroscopic inspection of the medial meniscus can lead to appropriate treatment with agood to excellent outcome after repair. Level of Evidence: Level IV, therapeutic case series.

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From the Department of Orthopedic Surgery, Meir GeneralHospital, Sapir Medical Center (I.H.), Kfar Saba, Israel; SacklerFaculty of Medicine, Tel Aviv University (I.H.), Tel Aviv, Israel;and Hospital for Special Surgery, Weill Medical College of CornellUniversity (K.L., R.G.M.), New York, New York, U.S.A.

The authors report no conflict of interest.Received September 13, 2010; accepted June 17, 2011.Address correspondence to Robert G. Marx, M.D., M.Sc.,

F.R.C.S.C., Hospital for Special Surgery, Weill Medical College ofCornell University, 535 E 70th St, New York, NY 10021, U.S.A.E-mail: marxr@hss.edu

© 2011 by the Arthroscopy Association of North America

0749-8063/10543/$36.00doi:10.1016/j.arthro.2011.06.025

1536 Arthroscopy: The Journal of Arthroscopic and Related Surg

Meniscocapsular separation is an uncommon in-jury.1 It is typically accompanied by ligament

ears (anterior cruciate ligament [ACL], posterior cru-iate ligament, medial collateral ligament).1-4 The in-ured area usually involves over 1 cm of disruptedeniscocapsular tissue, requiring several sutures for

epair.2,4

In this study we describe a series of patients whopresented with longstanding medial-side knee painthat followed low-energy knee trauma and did notrespond to nonoperative management. Magnetic res-onance imaging (MRI) scans, which used a 3-T mag-net in 5 cases and a 1.5-T magnet in 1 case, a sagittal

and coronal slice width of 3.5 mm, and no intersection

ery, Vol 27, No 11 (November), 2011: pp 1536-1542

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1537SMALL MEDIAL MENISCOCAPSULAR SEPARATIONS

gap, were negative in all cases. During arthroscopy,there was a detachment of less than 5 mm in length(measured with the right angle tip of the arthroscopicprobe used as a scale) at the capsular attachment of themedial meniscus posterior horn or posterior horn–body junction area. The injury was identified by in-serting the tip of the arthroscopic probe into the lesionshowing meniscal instability. Contrary to previouslydescribed meniscocapsular separations, no other sig-nificant intra-articular abnormalities or ligament dis-ruptions accompanied the injury. The purpose of thisstudy is to describe clinical characteristics and surgi-cal findings of this pathology, as well as to reportfunctional outcome after arthroscopic repair. We hy-pothesized that a good to excellent outcome isachieved after repair of this type of meniscocapsularseparation.

METHODS

This study includes 6 consecutive patients who un-erwent surgery by the senior author (R.G.M.) at aingle institution between January 2007 and May009. Office charts, MRI scans, operative reports, andrthroscopic images were reviewed. Inclusion criteriaere medial-side knee pain unresponsive to nonop-

rative management (i.e., activity modification andhysical therapy), physical examination findings indi-ating tenderness on palpation of the medial joint line,egative MRI findings, and an isolated meniscocap-ular separation injury detected on arthroscopy andepaired with only 1 stitch. In 5 patients the magneticesonance (MR) magnet was 3 T and in 1 case it was

TABLE 1. Patient Demographics, In

CaseNo.

Age(yr) Sex Injury Mechanism

Symptom-RelatedActivity

1 17 F Twisting and pivotingduring soccer

Twisting andpivoting duringsoccer

2 14 F Twisting and pivotingduring soccer

Running

3 17 F Twisting and pivotingduring lacrosse

Long walks, running,twisting, pivoting

4 15 F Jump landing duringgymnastics

Jumping

5 18 F Twisting duringfigure skating

Long walks, stairs,twisting

6 48 M Jump landing Long walks, jogging,running

1.5 T. Sequences included fast spin-echo sagittal, ax-ial, and coronal images, as well as inversion recoverysagittal sequence images, performed with and withoutfat suppression. Sagittal as well as coronal slice widthwas 3.5 mm with no intersection gap between slices.The repair technique included debridement of the me-niscocapsular damaged tissue with a 4.5 mm full-radius shaver, followed by a single all-inside No. 2-0nonabsorbable suture in a horizontal-oblique configu-ration. The intercondylar notch, just anterior to theACL, was then debrided with the shaver, causingsome bleeding to potentially promote healing of therepair. The postoperative protocol included 3 weeks ofnon–weight bearing and knee motion in a brace lim-ited to 0° to 90° until 6 weeks. After 3 weeks, fullweight bearing was allowed. After 6 weeks, full mo-tion was allowed, except squatting. Running was al-lowed at 4 months and squatting with unrestrictedactivities at 6 months. Patients were contacted andcompleted functional questionnaires that includedsubjective International Knee Documentation Com-mittee score, Tegner activity level score, and Marxactivity level score. Descriptive statistics included in-dividual as well as mean values for the functionalscores. The study was approved by our institutionalreview board, and all participants signed informedconsent forms.

RESULTS

Table 1 presents patient demographics, injury char-acteristics, and surgical findings. Of the 6 patients, 5were female aged 14 to 18 years who were involved in

haracteristics, and Surgical Findings

RI Magnet and Interpretation

SymptomsDuration

FromInjury toSurgery

Area of MedialMeniscocapsularSeparation and

Procedure

rmal findings 3 mo Posterior horn–bodyjunction, 1 all-inside stitch

rmal findings 2 yr Posterior horn, 1all-inside stitch

ild knee effusion, patellarnosis

1 yr Posterior horn–bodyjunction, 1 all-inside stitch

rmal findings 3 yr Posterior horn, 1all-inside stitch

rmal findings 6 mo Posterior horn, 1all-inside stitch

ld knee effusion, otherwise normalngs

9 yr Posterior horn–bodyjunction, 1 all-

jury C

M

3 T, no

3 T, no

1.5 T, mtendi

3 T, no

3 T, no

3 T, mifindi

inside stitch

1538 I. HETSRONI ET AL.

sports. All patients could recall an acute injury initi-ating their symptoms, which involved knee twistingduring sports activity or landing from a jump. Symp-toms were related mainly to sports and were absent orvery minimal during activities of daily living. Physicalexamination in all patients showed tenderness on pal-pation of the medial joint line. Other provocativemeniscal tests showed uncomfortable squatting (i.e.,the position of a baseball catcher) in 5 of the 6 patientsand a positive McMurray test in 4 patients. Kneeexamination was otherwise normal in all cases (i.e.,ligament stability maintained and no effusion). TheMRI scans did not show any meniscus or menisco-capsular injury pattern (Fig 1). The duration of symp-toms from injury to surgery was between 6 monthsand 9 years in 5 cases. For 1 patient (case 1), thedecision was made to proceed with surgery after only3 months because the patient was unable to run andshe wanted to return to competitive soccer for theupcoming season. During arthroscopy, all patients hada small medial meniscocapsular separation that wasrepaired with a single all-inside stitch. Before beingoperated on at our institution, 1 patient (case 3) had ahistory of negative arthroscopy findings with persis-

FIGURE 1. A 3-T MRI sagittal slice of a right knee not showingabnormality at the medial meniscus posterior horn–body junctionarea of a patient, where a small meniscocapsular separation wasfound later during arthroscopy. The inset shows a coronal view,indicating the location of the sagittal slice (white line), which

corresponds to the posterior horn-body junction area of the medialmeniscus.

tent symptoms. In this case the symptoms resolvedafter repair of the small meniscocapsular separation.

Figures 2 through 5 show the arthroscopic findings.This included a normal-appearing medial meniscusviewed from the anterior-lateral portal (Fig 2). Whenthe lesion involved the posterior horn–body junctionarea, it could be clearly seen when the tip of the probewas inserted into the defect (Fig 3). In cases involvingthe posterior horn, the lesion was identified when thetip of the probe was inserted above and beyond thehighest peripheral rim of the meniscus into the lesion,and the meniscus was then pulled slightly underneath

FIGURE 2. Normal-appearing medial meniscus viewed fromanterior-lateral portal.

FIGURE 3. A lesion involving the posterior horn–body junctionarea is clearly seen when the tip of the probe is inserted into the

defect. The arrow points to the lesion. The dashed line overlies themeniscocapsular junction. (MFC, medial femoral condyle.)

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1539SMALL MEDIAL MENISCOCAPSULAR SEPARATIONS

the medial femoral condyle, showing instability of themeniscus (Fig 4). This instability could be shownwhen the probe was inserted into the lesion fromunderneath the meniscus as well. The lesion was re-paired with 1 all-inside No. 2-0 suture (Fig 5).

At the routine 6-month follow-up visit, medial jointline tenderness resolved in all patients. The meanlatest follow-up was 31 months (Table 2). Five pa-tients had a minimum of 24 months’ follow-up. Themean subjective International Knee Documentation

FIGURE 4. A lesion (arrow) involving the posterior horn is iden-ified when the tip of the probe is inserted above and beyond theighest peripheral rim of the meniscus into the lesion. The menis-us is pulled underneath the medial femoral condyle (MFC), show-ng instability of the meniscus.

FIGURE 5. The lesion is repaired with 1 all-inside suture. Thearrow points to the meniscocapsular lesion area after it is repaired.

The dashed line overlies the meniscocapsular junction. (MFC,medial femoral condyle.)

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Committee score was 87 at latest follow-up. TheTegner and Marx scores showed that after surgery, 5patients regained their preinjury level of activity com-pletely or almost completely. These patients also re-ported specifically that their medial pain resolved dur-ing sports activity. Four of these involved high-levelcompetitive sports. In 1 patient, a 17-year-old girl(case 3), symptoms resolved after surgery, and shereturned to full activity. However, at 15 months aftersurgery, her medial pain gradually recurred. We there-fore suspected failure of the repair, and she was sched-uled to undergo revision arthroscopy. On revision, itwas apparent that the suture had pulled through themeniscus, leading to a larger tear (Fig 6). A revision

TABLE 2. Functional Scores

CaseNo.

LatestFollow-up

(mo)

SubjectiveIKDC

Score atLatest

Follow-upTegner Score(BI, BIS, C)

Marx Score(BI, BIS,

C)

1 38 99 9, 7, 7 16, 8, 162 38 * 9, *, 9 16, *, 163 15 72 9, 2, 6 16, 0, 34 35 87 9, 7, 9 12, 8, 125 24 93 9, 2, 7 12, 4, 116 36 85 4, 4, 4 8, 4, 8

Mean 31 87 8, 4, 7 13, 5, 11

Abbreviations: IKDC, International Knee Documentation Com-mittee; BI, before injury; BIS, between injury and surgery; C,current (at latest follow-up).

*Information unavailable (incomplete patient compliance).

FIGURE 6. Revision arthroscopy image showing a meniscus tear

aused by the primary meniscocapsular repair suture, which hadulled through the meniscus.

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1540 I. HETSRONI ET AL.

repair was carried out with a vertical outside-in repairusing 2 sutures (Fig 7).

DISCUSSION

Meniscocapsular separation is a rare injury that isypically accompanied by ligament tears.1-4 The sep-ration usually involves more than 1 cm in length andequires several stitches for repair.2,4 The lesions de-cribed in this study may therefore represent a uniqueubgroup of meniscocapsular separations because thisnjury was an isolated injury, involved not more than

mm in length, was occult on MRI and hard toisualize on arthroscopy, and required only 1 stitch forepair.

The data provided show that patients presentingith this injury share several characteristics. These

elate to patient demographics, mechanism of in-ury, and symptom characteristics, as well as surgi-al findings.Of the 6 patients, 5 were female teenagers involved

n cutting and pivoting sports, and all 6 patients couldecall a specific noncontact knee injury that initiatedhe symptoms. We cannot explain the reason foroung female predominance. Theoretically, this maye related to the soft-tissue characteristics of the cap-ular attachment or to specific anthropometric charac-eristics of bone morphology and joint congruency, asell as sex-specific joint kinematics that may put theosterior medial meniscocapsular tissue under tensiletresses specifically in female patients. It has been shown

FIGURE 7. Revision vertical outside-in repair was carried out byse of 2 sutures.

hat female patients have a poorer jump-landing tech- r

ique than male patients, characterized by less kneend hip flexion, more knee valgus moment and hipnternal rotation motion, and greater knee joint load-ng.5 Although this may contribute to the increasedisk of ACL injuries in female patients, in theory, suchower limb mechanics may contribute to subtle medial-ide knee injuries as well. The injury at the menisco-apsular area may be an example of this, which couldccur during a lower magnitude of forces comparedith those required to result in an ACL injury. Frompractical clinical standpoint, this observation may

aise the index of suspicion for this injury in thispecific age group of female patients when medial-ide knee pain after a twisting knee injury fails toespond to nonoperative treatment.

In 4 cases the duration of symptoms was between 1nd 9 years from injury to surgery. Although allatients were clearly symptomatic during sports be-ause of medial-side knee pain, their overall favorableunction in daily activities permitted them to continueith nonoperative management for a prolonged dura-

ion. This could be related to 2 major factors in ourpinion. First, because the separation was of smallagnitude, we believe high loads (encountered during

ctivities such as cutting or jumping) are required toause meniscal displacement at the richly innervatedapsule and therefore pain at the site of injury. Thus,ctivities of daily living that involve walking may notause sufficient tension to displace the meniscus andtress the capsule to cause pain. Second, because theeriphery of the meniscus is vascularized, some heal-ng, though not optimal, may have taken place in somef these cases. In such a scenario, the partially healedeniscocapsular area may support activities of daily

iving but may not have been able to support highertresses as encountered during sports.

The physical examination findings in all 6 caseshowed at least 1 positive sign suggestive of a menis-us or meniscocapsular injury. Whereas McMurrayests and medial pain during full flexion were notositive in all cases, the medial joint line was alwaysender to palpation. This emphasizes the importancef medial joint line palpation specifically in this typef injury, because other common tests may not beensitive enough.

The MRI findings, despite use of a 3-T magnet in 5f 6 patients, were negative for meniscus or menisco-apsular injury. Several subtle diagnostic criteria anditfalls on MRI have previously been described toelp in the diagnosis of injuries to the meniscocapsu-ar area. These included meniscal displacement, pe-

ipheral meniscal corner tears, increased perimeniscal

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1541SMALL MEDIAL MENISCOCAPSULAR SEPARATIONS

signal intensity, and fluid deep to the medial collateralligament.6 However, even when Rubin et al.1 evalu-ated MR images prospectively and retrospectively inrelation to knee arthroscopy to evaluate the accuracyof MRI to diagnose meniscocapsular injuries, lookingfor the previously mentioned specific signs, the posi-tive predictive value of the MRI was less than 10%. Itis not surprising therefore that the small lesion de-scribed in our patients was not detected on MRI. Wethus agree that because of the size of the lesion, it mayhave been missed on the MRI scans. Another potentialexplanation for the negative MRI findings may berelated to the fact that MRI is performed with thepatient lying supine, and therefore, with no body weightapplied to the meniscus, it may not be displaced (theselesions were asymptomatic during everyday activities aswe described), concealing its existence.

MR arthrography is another option that could in-crease the sensitivity of intra-articular pathology di-agnosis. However, it has been shown that althoughthis MR modality may theoretically document inter-position of contrast media between the meniscus andthe medial collateral ligament, practically, this findingwas present in the minority of knees with menisco-capsular separations, putting into question the useful-ness of this diagnostic tool.7 In addition, if significantdema or fibrosis is present in the area of the menis-ocapsular injury, contrast material may not locate inhis area.7 We proceeded with surgery in our patientsespite the negative imaging in view of the duration ofymptoms and limitation in function. It was decidedhat the potential benefits from arthroscopic interventionutweighed the risk of negative arthroscopy finding.Arthroscopy should always follow an orderly ex-

mination with probing all knee compartments tovoid overlooking a subtle injury. The cases presentedhow how important this probing is, specifically in theedial meniscocapsular area. The meniscocapsular

esions presented in this study were not obvious byiewing with the 30° arthroscope from the anterior-ateral portal. Adhering to principles as previouslyescribed,8 as well as careful probing of the menisco-

capsular area from above and underneath the medialmeniscus allowed identification of the lesion. This isof specific interest in 1 of our cases in which a pre-vious arthroscopy had been performed at another in-stitution after the initial injury but did not identify theseparation. Because symptoms persisted after that pro-cedure despite a long period of rehabilitation, werepeated the arthroscopy and repaired the lesion. This

case emphasizes the importance of being aware of this

injury and the careful critical probing of the menisco-capsular area.

The functional scores in 5 of 6 patients support ourhypothesis, showing that a good to excellent outcomewith return to preinjury level of activity is achievedafter repair of the lesion. This is likely related to therich vascularity of the periphery of the meniscus,which provides excellent healing potential in this area.

Long-standing medial-side knee pain after noncon-tact knee injury should not be routinely diagnosed asmeniscus or meniscocapsular lesion. Other sources ofdiscomfort in this area include medial collateral liga-ment injuries, articular cartilage injuries, bone bruise,patellofemoral pain, and radicular symptoms from ei-ther the hip joint or the lower lumbar spine. Beforeany arthroscopic procedure is performed to address asuspected meniscus pathology or meniscocapsular le-sion, care must therefore be applied to rule out theseand other sources of pain that may respond to anonoperative approach. At the same time, clinicalsuspicion should be applied to possible uncommonlesions when history and physical examination sup-port an intra-articular source for symptoms. An exten-sive period of nonoperative treatment and watchfulwaiting are therefore appropriate before consideringarthroscopy.

Weaknesses of this study include the small numberof cases, as well as the retrospective nature of thestudy, which makes it impossible to estimate accu-rately the prevalence of this injury in the population.

CONCLUSIONS

Meniscocapsular separation can involve a segmentof less than 5 mm in length, be occult on MRI, bechallenging to visualize on arthroscopy, and lead tochronic medial-side knee pain. Critical evaluationwith a history, physical examination, and careful ar-throscopic inspection of the medial meniscus can leadto appropriate treatment with a good to excellent out-come after repair.

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3. Potter HG, Weinstein M, Allen AA, Wickiewicz TL, Helfet DL.

Magnetic resonance imaging of the multiple-ligament injuredknee. J Orthop Trauma 2002;16:330-339.

1542 I. HETSRONI ET AL.

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7. De Maeseneer M, Lenchik L, Starok M, Pedowitz R, Trudell D,Resnick D. Normal and abnormal medial meniscocapsularstructures: MR imaging and sonography in cadavers. AJR Am JRoentgenol 1998;171:969-976.

6. De Maeseneer M, Shahabpour M, Vanderdood K, Van RoyF, Osteaux M. Medial meniscocapsular separation: MR im-

8. Carson WG Jr. Arthroscopic techniques to improve access toposterior meniscal lesions. Clin Sports Med 1990;9:619-632.