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  ORIGINAL ARTICLE  Diagnostic Value of History Taking and Physical Examinationto Assess Effusion of the Knee in Traumatic Knee Patients inGeneral Practice  Marlous Kastelein, MD, Pim A. Luijsterburg, PhD, Harry P. Wagemakers, MSc, Santusha C. Bansraj, MD, Marjolein Y. Berger, MD, PhD, Bart W. Koes, PhD, Sita M. Bierma-Zeinstra, PhD ABSTRACT. Kastelein M, Luijsterburg PA, WagemakersHP, Bansraj SC, Berger MY, Koes BW, Bierma-Zeinstra SM.Diagnostic value of history taking and physical examination toassess effusion of the knee in traumatic knee patients in generalpractice. Arch Phys Med Rehabil 2009;90:82-6. Objective:  To assess the diagnostic value of history takingand physical examination for knee joint effusion in patientswith a knee injury who consult their general practitioner (GP).In addition, to determine the association between effusion seenon magnetic resonance imaging (MRI) and internal derange-ment of the knee. Design:  Prospective, observational cohort study. Setting:  Primary care. Participants:  Patients (N  134) aged 18 to 65 years with atraumatic knee injury who consulted their GP. Interventions:  Not applicable. Main Outcome Measures:  Patients filled out a question-naire, underwent a standardized physical examination and un-derwent an MRI scan to assess the presence of effusion. Mul-tivariate logistic regression analysis was used to determine thediagnostic value of history taking and physical examination( P  0.10) as assessed by sensitivity, specificity, predictivevalues, and likelihood ratios. The relationship between effu-sion and internal derangement of the knee was assessed with achi-square test. Results:  Of the 134 participating patients, 42 had knee jointeffusion seen on MRI. Multivariate analysis showed an asso-ciation with knee joint effusion for the symptom “self-noticedswelling” (history taking) and for the “ballottement test” (phys-ical examination). The likelihood ratio positive (LR  ) was 1.5for self-noticed swelling and 1.6 for the ballottement test.These 2 combined improved the diagnostic value to an LR  of 3.6. Effusion showed a positive association with internal de-rangement of the knee (chi-square 9.5); 31 of the 42 patientswith knee joint effusion had internal derangement of the knee. Conclusions:  In patients with traumatic knee injury, knee joint effusion is frequently seen on MRI. The combination of self-noticed swelling and the ballottement test was of diagnos-tic value. Knee joint effusion was associated with internalderangement of the knee. Key Words:  History taking, medical; Knee injury; Magneticresonance imaging; Physical examination; Primary care; Reha-bilitation.©  2009 by the American Congress of Rehabilitation Medicine K NEE INJURY IS A FREQUENT reason to consult the GP.The incidence of traumatic knee injuries (excluding frac-tures) reported in Dutch general practice is about 5.3 per 1000patients per year. 1 Effusion is frequently seen in traumatic kneepatients and in secondary care a positive correlation betweeneffusion (MRI) and internal derangement of the knee is re- ported. 2 Additionally, Kolman et al 3 reported that symptom-atic patients with no significant effusion in the lateral aspect of the suprapatellar pouch on MRI are free of internal derange-ment in 86% of the cases. In the Netherlands, about 25% of allpatients presenting in general practice with traumatic kneeinjuries are referred to secondary care. 4 Therefore, in traumaticknee patients it would be useful if the GP could detect knee joint effusion by means of history taking and physical exami-nation.Various questions from history taking (eg, Is your kneeswollen?) and various physical examination tests are availableto evaluate the presence and amount of knee joint effusion.Tests from physical examination include palpation of effusionand/or Baker cyst in the fossa poplitea, 5 the peripatellarfluctuation test (minor effusion test), 5 and the floating pa-tella test (ballottement test). 5,6 However, the diagnostic valueof history tak ing and physical examination is often questionedby clinicians. 7,8 Further, in routine practice it is still unclearwhat the diagnostic value of history taking and physical exam-ination is, when and which test to use, and which test is mosteffective to evaluate effusion.The present study aims to determine the diagnostic value of items from history taking and physical examination in detect-ing effusion of the knee joint as seen on MRI in traumatic kneepatients in primary care. The second aim is to investigate theassociation between effusion seen on MRI and internal de-rangement of the knee in this primary care population. MRIwas selected as the reference test because it is a highly accuratediagnostic tool for detecting effusion of the knee joint. 3,9 From the Department of General Practice, Erasmus University Medical Center,Rotterdam, The Netherlands.Supported by TRIAS, Zilveren Kruis Achmea, and OZ.No commercial party having a direct financial interest in the results of the researchsupporting this article has or will confer a benefit on the authors or on any organi-zation with which the authors are associated.Correspondence to Marlous Kastelein, MD, Dept of General Practice, ErasmusMedical Center Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands,e-mail:  m.kastelein@erasmusmc.nl.  Reprints are not available from the author.0003-9993/09/9001-00335$36.00/0doi:10.1016/j.apmr.2008.06.027 List of Abbreviations CI confidence intervalGP general practitionerLR   likelihood ratio positiveLR   likelihood ratio negativeMRI magnetic resonance imagingOR odds ratioPVN predictive value – negativePVP predictive value – positive 82 Arch Phys Med Rehabil Vol 90, January 2009  METHODSPatients The present study was performed within the HONEUR kneecohort 10 (a prospective, observational cohort study of patientsconsulting the GP for all types of new knee complaints). In thepresent study, patients who had a traumatic knee complaint lessthan 5 weeks before consultation and were aged 18 to 65 years,but had no MRI contraindications (pregnancy, metal implants,or a pacemaker), were asked for informed consent for anadditional MRI. Data Collection An appointment was made for the MRI and patients filledout a baseline questionnaire 10 which they had to bring along atthe MRI examination. A standardized physical examination 10 was performed immediately after the MRI by a trained physicaltherapist. The physical therapist was blinded for the MRIresults, as was the radiologist who scored the MRI for theresults of the physical examination and questionnaire. Boththe patient and the GP were not informed about the outcomeof the MRI or physical examination; this was to avoidinfluencing the behavior of the patient, or the managementby the GP during follow-up.The baseline questionnaire collected data on age, sex, socio-economic status, history of previous knee injuries and/or op-erations, present symptoms, mechanism of injury, level of activity in work, household, study and sports, pain severity, andthe Lysholm knee score. 11 Physical examination of both kneesconsisted of inspection, palpation, assessment of effusion, pas-sive range of motion in flexion and extension, knee stabilitytests, and meniscal tests. In the present study we focused on thequestion: did the patient notice any swelling of the knee and onthe following tests (see Appendix 1): palpation of effusion orBaker cyst in the fossa poplitea, the peripatellar fluctuation test(minor effusion test), and the floating patella test (ballottementtest). 5,6 MRI was scheduled 3 to 6 weeks after the initial trauma andwas performed with a 1.0 Tesla device. a Two radiologistsclassified the MRI scans independently from one another. De-tailed inf ormation about the MRI procedure is reported else-where. 12 Regarding effusion, patient outcome was defined as absent,small (fluid in 1 or 2 compartments), moderate (fluid in 3compartments), or severe (fluid in 3 compartments with bulg-ing of the capsule and pericapsular soft tissue) knee jointeffusion (accumulation of intra-articular fluid in suprapatel-lar, medial or lateral compartment) as seen on MRI. 12 In thisstudy we dichotomized effusion into none to small versusmoderate to severe effusion. We designated moderate to severeeffusion as being clinically important effusion.The study protocol was approved by the Medical Ethicscommittees of the Erasmus Medical Center Rotterdam and of the Medical Center Rijnmond Zuid. Statistical Analysis Descriptive statistics were used to present the results of theMRI. Univariate logistic regression analysis b was used to de-termine the association between knee joint effusion and sepa-rate symptoms from history taking and signs from physicalexamination, expressed as OR. The symptoms and signs indi-cating a univariate association ( P  0.10) with knee joint effu-sion were analyzed with multivariate logistic regression anal-ysis (Backward Wald method, entry 0.10, removal 0.20).We determined the diagnostic value of the isolated symp-toms from history taking and signs from physical examinationby calculating the sensitivity, specificity, PVP and PVN. 13 Wealso determined the likelihood ratio for positive and negativeexamination. 13 In general, an LR   of 1 to 2 or an LR  between 0.5 and 1 changes the probability of the presence orabsence of knee joint effusion by only a small degree. 14 AnLR   of 2 to 10 or an LR   between 0.1 and 0.5 may beconsidered clinically important. 14 An LR   greater than 10 oran LR   less than 0.1 may have substantial impact on theprobability of the diagnosis. Finally, we combined symptomsand signs from the composed diagnostic model for knee jointeffusion ( P  0.10) and determined the diagnostic value of thesecombinations.The relationship between effusion and internal derangementof the knee (cruciate ligament lesion and/or meniscal lesionwith the exception of degenerative lesions) was assessed witha chi-square test with a significance level of 0.05. RESULTSStudy Population Of the 184 eligible patients, 134 (73%) were included in thepresent study. No significant differences were found betweenthe baseline characteristics of the participants and non-partic-ipants (data not shown). Table 1 presents the characteristics of the participating patients.Of the 134 participating patients, 61 (45.5%) reported thatthe knee injury was caused by sport activities. Mean age  SDof the participants was 40.2  12.2 years and 55.2% were men. Magnetic Resonance Imaging Results Table 1 also gives the MRI results. The average periodbetween trauma and MRI was 38 (range, 9–81) days; 70% of all patients had their MRI within 6 weeks after the initialtrauma. From these 134 traumatic knee patients, 50% had smalleffusion, 26.9% had moderate effusion, and 4.5% had severeeffusion. Clinically important effusion (moderate and severeeffusion) detected by MRI was seen in 42 patients (31.3%). In31 (73.8%) of the 42 patients with clinically important effusiona cruciate ligament lesion or meniscal tear was seen on MRI; a Table 1: Characteristics of the Participants (N  134) and Diagnosisas Seen on MRI n (%) CharacteristicMean age  SD (y) 40.2  12.2Sex, men 74 (55.2)Onset during sports activity 61 (45.5)Symptom side right 70 (52.2)Pain severity (0–10), mean  SD 4.7  2.4Lysholm knee function score (0–100), mean  SD 63.7  18.9Diagnosis as seen on MRINo lesion or effusion* 14 (10.4)Contusion (effusion* with no ligament or meniscallesion) 38 (28.4)Clinically important effusion † 42 (31.3)Medial collateral ligament lesion 35 (26.1)Lateral collateral ligament lesion 8 (6.0)Anterior cruciate ligament lesion 28 (20.9)Posterior cruciate ligament 6 (4.4)Meniscal tear 47 (35.1)NOTE. Values are n (%) unless otherwise noted.*Effusion: small, moderate, and severe effusion. † Clinically important effusion: moderate and severe effusion. 83 DIAGNOSTIC VALUE FOR EFFUSION OF THE KNEE, KasteleinArch Phys Med Rehabil Vol 90, January 2009  positive association (OR  5.0; 95% CI, 2.2–11.1) of clinicallyimportant effusion with internal derangement of the knee couldbe shown (   2 9.5,  P  0.002). History Taking and Physical Examination Of the 134 patients, for 128 patients (95.5%) both the historytaking and the physical examination were available. Table 2shows the association between items from history taking andphysical examination with knee joint effusion.From history taking self-noticed swelling showed an asso-ciation with effusion, with an OR of 4.8 (95% CI, 2.0–11.6)(see table 2). Two test results obtained by physical examination (effusion fossa poplitea and positive ballottement test) showedan association with effusion with an OR of 2.1 (95% CI,0.9–5.0) and 5.1 (95% CI, 2.0–12.6), respectively.Table 3 shows the multivariate association of items fromhistory taking and physical examination with effusion.After multivariate modelling self-noticed swelling from his-tory taking and the ballottement test from physical examinationshowed an independent association with the presence of effu-sion with an OR of 5.3 (95% CI, 2.1–13.6) and 5.7 (95% CI,2.2–15.2), respectively. Diagnostic Value of History Taking and PhysicalExamination In this study population the prevalence of effusion (priorprobability) was 0.31 (42 of 134). Table 4 presents the diag-nostic value of history taking and physical examination.The PVP of effusion increased from 0.31 to 0.40 (95% CI,0.29–0.51) for self-noticed swelling and to 0.43 (95% CI,0.32–0.53) for the ballottement test. The PVP increased to 0.62(95% CI, 0.47–0.77) when self-noticed swelling from historytaking and the ballottement test from physical examinationwere both present.The probability of the absence of effusion increased from0.69 to 0.83 (95% CI, 0.73–0.94) if self-noticed swelling wasabsent and to 0.86 (95% CI, 0.77–0.96) if the ballottement testwas negative. Absence of self-noticed swelling together with anegative ballottement test did not further increase the PVN.The isolated symptom self-noticed swelling and the ballotte-ment test showed an LR   of 1.5 (95% CI, 1.1–1.9) and 1.6(95% CI, 1.3–2.1), respectively; altering the likelihood of ef-fusion by only a small degree. The LR   increased to a clini-cally important value of 3.6 (95% CI, 2.2–5.9) when thesymptom self-noticed swelling from history taking and theballottement test from physical examination were both present.The symptom self-noticed swelling and the ballottement testhad a clinically important LR  of 0.4 (95% CI, 0.2–0.9) and0.3 (95% CI, 0.2–0.7), respectively. Absence of self-noticedswelling together with a negative ballottement test did notfurther decrease the LR  . DISCUSSION The present study is the first to investigate the diagnosticvalue of history taking and physical examination for kneeeffusion seen on MRI, among patients in a primary care setting.Clinically important effusion was seen in 31.3% of these 134patients.In the present study the isolated symptom self-noticed swell-ing from history taking and the ballottement test from physicalexamination showed diagnostic value in detecting and more-over in excluding knee joint effusion. Combining the symptomfrom history taking and the sign from physical examinationresulted in a more clinically important PVP and LR  . In thiscase GPs can predict with a 62% chance whether there is knee joint effusion, but still cannot be certain about the actualpresence of effusion. Further, GPs can reasonably exclude(with an 83%–86% chance) knee joint effusion when self-noticed swelling and/or the ballottement test is negative, whichcould help to avoid unnecessary diagnostic interventions. How-ever, Boks et al 12 showed that in case of absence of effusionsome patients still have internal derangement of the knee.To our knowledge, the only other study addressing thedetection of knee joint effusion focused on the accuracy of sonographic examination. Wang et al 15 reported a sensitivity,specificity, PVP and PVN of sonographic examination (com-pared with MRI) for detecting knee effusion. They concludedthat sonographic examination can accurately detect effusion of the knee. Compared with Wang, our study showed equal sen-sitivity and specificity for self-noticed swelling and the bal-lottement test. Combining self-noticed swelling and the bal-lottement test in our study showed a lower sensitivity, but ahigher specificity. Further, our study showed lower PVPs, butmuch higher PVNs for self-noticed swelling, the ballottementtest, and the combination of both.In the present study during history taking we asked thepatient whether they had noticed a swelling of the knee; theanswer to this question could be no, sometimes, or always. Forthe statistical analysis we dichotomized the answers into  no versus  sometimes  and  always . Alternatively, dichotomizing theanswer into  no  and  sometimes  versus  always  did not improvethe results.Further, from physical examination only the ballottementtest showed an association with knee joint effusion. Miller etal 16 found a significant association between Baker cyst and effu- Table 3: Multivariate Association (and 95% CI) of Items With KneeJoint Effusion Variable From History Taking orPhysical ExaminationEffusion Moderate/Severe* OR95% CI History takingSelf-noticed swelling 5.3 † (2.1–13.6)Physical examinationBallottement test 5.7 † (2.2–15.2)Explained variance (%) 27.9*As detected on MRI. † P   0.05. Table 2: Number of Patients With Positive Test Result andUnivariate Association of Items With Knee Joint Effusion VariablesPatientsAvailablenEffusionModerate/ Severe*(n  42)EffusionAbsent/ Small*(n  91) OR 95% CI History takingSelf-noticedswelling 128 32 40 4.8 ‡ 2.0–11.6Physical examinationEffusion fossapoplitea 5 129 31 55 2.1 † 0.9–5.0Bakers cyst fossapoplitea 5 129 5 7 1.7 0.5–5.6Fluctuation/Minoreffusion test 5 127 6 7 2.0 0.6–6.4Ballottement test 5,6 131 34 44 5.1 ‡ 2.0–12.6*As detected on MRI. † P   0.10. ‡ P   0.05. 84  DIAGNOSTIC VALUE FOR EFFUSION OF THE KNEE, KasteleinArch Phys Med Rehabil Vol 90, January 2009  sion, whereas we did not. An explanation for this difference couldbe that we had only 12 patients with a Baker cyst and (in contrastto Miller et al 16 ) we palpated for a Baker cyst instead of usingMRI, whereby a small Baker cyst could be missed.The literature 5,6 assumes that one can evaluate the presenceof effusion with the minor effusion test and the ballottementtest. However, our study shows that, of these 2 tests, only theballottement test has an association with clinically importanteffusion. Although one might argue that the minor effusion testmay be better in detecting minor effusion, we even found noassociation between the minor effusion test and small or minoreffusion.Discussion remains about interpretation of the ballottementtest. Is the test positive when you hear a click  5,6 or is it positivewhen you feel a floating patella? 5 In the present study weconsidered both a click and a floating patella to be a positivetest result. In most of our patients a positive ballottement testconcerned a floating patella (n  74) and only a few concerneda click (n  4).For the analyses we dichotomized effusion seen on MRI intonone to small and moderate to severe effusion, because Boks etal 12 reported that a small effusion was very common in asymp-tomatic knees and might not be clinically meaningful. Kolmanet al 3 also suggested that a small effusion (10mm or less in thelateral suprapatellar pouch seen on MRI) was not clinicallymeaningful, but rather a physiologic sign.The period between trauma and MRI was 38 (range, 9–81)days. In this period, natural healing of lesions (at least of haemathrosis, but also of effusion) might have occurred, andsome effusion might have changed from moderate or severe tosmall. Because history taking was assessed earlier than phys-ical examination and MRI, the relationship between historytaking and effusion on MRI could be underestimated.Because we had a relatively small study population(N  134) we have chosen to use a cutoff point of 0.10 in theunivariate analysis for inclusion in the multivariate model.However, the variables that remained in the multivariatemodel and were used for the diagnostic values both showedmuch lower  P  values ( P  0.05). Still, the results presentedhere should be validated in a larger study population ingeneral practice.The Dutch Clinical Guideline Traumatic knee disorders 17 for GPs reported that in case of effusion within a few hoursafter the trauma, in the presence of a positive ballottementtest or locking of the knee there is suspicion of internalderangement of the knee; they recommend a wait and seepolicy unless there is locking of the knee or suspicion of afracture. Some data are available concerning the clinicalvalue of effusion. Duncan et al 2 describe a positive corre-lation between effusion and internal derangement of theknee. In addition, Kolman 3 reported that symptomatic pa-tients with no significant effusion in the lateral aspect of thesuprapatellar pouch on MRI are free of internal derangementin 86% of the cases. Our study confirmed also a positiveassociation between clinically important effusion and inter-nal derangement of the knee. Additionally, and more impor-tant for GPs, is the question whether there is also an asso-ciation between history taking/physical examination(focused on effusion) and internal derangement of the knee.We found a small relationship between positive self-noticedswelling together with a positive ballottement test and in-ternal derangement of the knee (univariate logistic regres-sion, OR  1.9;  P  0.094), predicting a 59% chance of in-ternal derangement of the knee (data not shown). Thepresence of only the symptom self-noticed swelling showedalmost the same relationship with internal derangement of the knee, but the presence of only a positive ballottementtest did not show this relationship (data not shown). Basedon the present results we recommend the following: if GPssuspect effusion of the knee, because the patient has noticedswelling of the knee and the ballottement test is positive,they should consider the possibility of internal derangementof the knee. A wait and see policy is recommended unlessthere is locking of the knee or suspicion of a fracture.However, because of the association between effusion andinternal derangement of the knee, GPs might use the pre-dicted chance of effusion as a selection criterion for MRIand/or referral to secondary care. CONCLUSIONS Our study indicates that GPs can reasonably exclude knee joint effusion in patients with a knee trauma based on theabsence of self-noticed swelling and/or a negative ballotte-ment test. This could argue against further diagnostic inter-ventions, but the GP has to bear in mind that some patientswith knee joint effusion could be missed. The data also showthat GPs can predict knee joint effusion with a maximum of only 62% certainty, based on the presence of self-noticedswelling together with a positive ballottement test. In addi-tion, our study results support that knee joint effusion inprimary care patients is associated with internal derange-ment of the knee. Table 4: Diagnostic Values (and 95% CI) of Isolated Symptoms and Signs, and Combinations of Symptoms and Signs, With Knee JointEffusion (Prevalence  0.31/n  42) Variable n* SE SP PVP PVN LR   LR  Isolated symptoms and signsSelf-noticed swelling 72 0.80 0.45 0.40 0.83 1.5 0.4 † (0.68–0.92) (0.35–0.39) (0.29–0.51) (0.73–0.94) (1.1–1.9) (0.2–0.9)Ballottement test 78 0.83 0.49 0.43 0.86 1.6 0.3 † (0.71–0.94) (0.39–0.59) (0.32–0.53) (0.77–0.96) (1.3–2.1) (0.2–0.7)CombinationSelf-noticed swelling plusballottement test 42 0.67 0.82 0.62 0.85 3.6 † 0.4 † (0.52–0.81) (0.73–0.90) (0.47–0.77) (0.77–0.92) (2.2–5.9) (0.3–0.6)Abbreviations: SE, sensitivity; SP, specificity.*n  prevalence of the determinant or combination. † Clinically important LR. 85 DIAGNOSTIC VALUE FOR EFFUSION OF THE KNEE, KasteleinArch Phys Med Rehabil Vol 90, January 2009
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