Is there an alternative to the full-leg radiograph for determining knee joint alignment in osteoarthritis.код для вставкиСкачать
Arthritis & Rheumatism (Arthritis Care & Research) Vol. 55, No. 2, April 15, 2006, pp 306 –313 DOI 10.1002/art.21836 © 2006, American College of Rheumatology ORIGINAL ARTICLE Is There an Alternative to the Full-Leg Radiograph for Determining Knee Joint Alignment in Osteoarthritis? RANA S. HINMAN, RACHEL L. MAY, AND KAY M. CROSSLEY Objective. To assess the concurrent validity of alternative measures of frontal plane knee alignment, namely the radiographic anatomic axis and 5 clinical measures, in medial compartment knee osteoarthritis (OA) as compared with the mechanical axis on radiograph. Methods. Forty individuals (mean ⴞ SD age 64.7 ⴞ 9.4 years) with symptomatic medial knee OA participated. Knee alignment was measured according to the following methods: lower-limb mechanical axis on radiograph, lower-limb anatomic axis on radiograph, visual observation, distance between medial knee joint lines or medial malleoli using a calliper, distance between a plumb line and medial knee joint line or malleolus using a calliper, tibial alignment using a gravity inclinometer, and lower-limb alignment using a goniometer. Data were analyzed using Pearson’s correlation coefﬁcient or Spearman’s rho correlation coefﬁcient and simple linear regression. Results. The anatomic axis best correlated with the mechanical axis (r ⴝ 0.88), followed closely by the inclinometer method (r ⴝ 0.80). Other clinical measures of alignment that were signiﬁcantly associated with the mechanical axis were the calliper method, the plumb-line method, and visual observation (r ⴝ 0.76, 0.71, and ⴚ0.52, respectively). However, the goniometer method failed to correlate. Conclusion. The anatomic axis on radiograph and the inclinometer method appear to be valid alternatives to the mechanical axis on full-leg radiograph for determining frontal plane knee alignment in medial knee OA. These alternative methods of measuring knee alignment may increase the assessment of this parameter by clinicians and researchers alike, given that malalignment is an important indicator of disease progression and treatment outcome. KEY WORDS. Knee; Osteoarthritis; Alignment; Validity; Radiograph. INTRODUCTION Knee osteoarthritis (OA) is a common afﬂiction in the elderly population worldwide, affecting approximately one-third of individuals ⬎60 years of age (1). Typical consequences for the patient with knee OA include pain, reduced physical function, disability, and ultimately decreased quality of life. A range of musculoskeletal impairSupported by funding from The University of Melbourne and the Arthritis Foundation of Australia. Rana S. Hinman, BPhysio(Hons), PhD, Rachel L. May, Kay M. Crossley, BAppSci(Physio), GradDip(Physio), PhD: Centre for Health, Exercise and Sports Medicine, School of Physiotherapy, The University of Melbourne, Victoria, Australia. Address correspondence to Rana S. Hinman, BPhysio(Hons), PhD, Centre for Health Exercise and Sports Medicine, School of Physiotherapy, The University of Melbourne, Parkville, Victoria, 3010, Australia. E-mail: ranash@ unimelb.edu.au. Submitted for publication May 20, 2005; accepted in revised form August 26, 2005. 306 ments are also associated with the condition. These may include, but are not limited to, muscle weakness, impaired proprioception, altered gait patterns, and joint laxity (2– 6). Because there is no cure for OA, current management strategies aim to relieve symptoms and slow the progression of the disease (7,8). Joint malalignment in the frontal plane is a frequent manifestation of knee OA, but it is not clear whether it precedes disease onset or occurs as a consequence. Varus malalignment appears to be the most common deformity, and has been reported in 53–76% of individuals with knee OA (9 –11). This is probably a result of the high prevalence of medial tibiofemoral OA relative to lateral compartment disease (12,13), whereby progressive cartilage loss on the medial side may lead to increasing varus deformation of the knee joint. Frontal plane malalignment has important biomechanical consequences because it inﬂuences loading across the knee joint during weight bearing. In the neutrally aligned knee, the ground reaction force vector passes medially to the joint center, creating an adduction moment that increases medial compartment forces relative to lat- Determining Knee Alignment in OA eral (14). When the knee is malaligned in the varus direction, the moment arm for ground reaction force vector is increased, resulting in a higher adduction moment than that observed in the neutral knee. Valgus malalignment results in a more laterally positioned ground reaction force vector and increases forces across the lateral knee compartment. OA is believed to result from the interplay between alterations in loading across the knee joint surfaces and genetic susceptibility (15). Although many factors, such as obesity and repetitive activity (16), may increase joint loading and lead to the development or progression of knee OA, malalignment is a strong predictor of disease progression. In a study of 230 individuals with knee OA, Sharma et al (17) demonstrated that varus malalignment at baseline was associated with a 4-fold increase in the risk of medial compartment progression at 18 months as measured by joint space narrowing on radiograph. Valgus malalignment was associated with an almost 5-fold increase in the risk of lateral compartment progression. These ﬁndings are supported by ﬁndings from other studies (11,18). Similar associations between malalignment and risk of OA progression have also been reported for the patellofemoral joint (9). No study to date has evaluated the effect of knee malalignment on incident knee OA. In knee OA, malalignment in both knees of ⬎5° in either a varus or valgus direction is associated with signiﬁcantly greater functional decline over time when compared with less malaligned knees (17). Malalignment adversely inﬂuences the outcome of surgical interventions for knee OA, such as arthroplasty and high tibial osteotomy (19,20). It also mediates the effect of body weight on disease progression, whereby the detrimental effect of body mass index on progression appears to be limited only to knees with moderate malalignment (11). Despite the importance of identifying malalignment in patients with knee OA, assessment of malalignment remains problematic. The gold standard for assessment is the weight-bearing full-leg radiograph, which allows the mechanical axis of the lower limb to be determined. This procedure is costly, exposes the patient’s pelvis to ionizing radiation, and is not feasible for many health care professionals and researchers who are unable to directly request radiographs funded by national health care systems. Furthermore, the evaluation of alignment from the radiograph requires extrapolation of the femoral and tibial mechanical axes using bony landmarks, thus it is somewhat time consuming for the clinician or researcher to determine. Determination of knee alignment using the anatomic axis (21,22) is possible from a single knee radiograph. This is a cheaper alternative, exposes the patient to less radiation, and is a routine test ordered for many patients with knee OA; however, the validity of this technique for measuring the mechanical axis in knee OA has only been reported in abstract form (23). Several clinical measures of knee alignment have been reported in the literature, including goniometry (24), visual observation (25), and calliper methods of measurement (26). Although such methods offer great clinical application with regard to cost, simplicity of use, 307 and speed of result, no clinical measure of knee alignment has been validated against the mechanical axis determined by radiography. This study assessed the concurrent validity of the radiographic anatomic axis and 5 clinical measures of frontal plane knee alignment in medial compartment knee OA. The aim of this study was to determine the correlation between these measures and the mechanical axis on radiograph, which is considered the gold standard for determining knee alignment. PATIENTS AND METHODS Participants were recruited for a cohort study evaluating laterally wedged insoles. Forty participants ⬎50 years of age with medial compartment knee OA were recruited from the community by newspaper advertisements. Diagnosis was based on the American College of Rheumatology classiﬁcation criteria (27). Participants were included if they had osteophytes in the medial tibiofemoral joint compartment on radiograph, experienced knee pain on most days of the past month, and reported an average pain while walking of ⬎3 on an 11-point Likert scale in the last month. Participants were excluded if they reported a previous hip or knee joint replacement, hip or lumbar spine arthritis or other joint pathology causing lower-limb pain, a knee injection in the preceding 6 months, knee surgery in the preceding 6 months, use of shoe orthotics in the preceding 6 months, a body mass index ⬎36 kg/m2, use of gait aid, or an inability to understand English. Ethics approval was obtained from the University of Melbourne’s Human Research Ethics Committee, and from the Department of Human Services’ Radiation Advisory Committee. All participants provided written informed consent prior to entering the study. Knee joint alignment as determined by mechanical axis. A single full-leg, anteroposterior, weight-bearing radiograph of the symptomatic lower limb was obtained. Either a 35.6 ⫻ 91.4 – cm graduated-grid cassette or a standard (nongraduated) 35.6 ⫻ 129.5– cm cassette was used, depending on the height of the participant. Care was taken when using the nongraduated cassette, such that clarity of the femoral head, knee joint, and talus was achieved on all images. Participants stood barefoot with the knee in full extension, and were positioned with the tibial tuberosity facing the x-ray beam (17). Weight was distributed equally over both feet. The x-ray tube was positioned at a distance of 2.44 meters from the cassette, and depending on individual limb characteristics, a setting of ⬃25 mA/second and 100 kilovolts was applied. Foot maps were drawn for each participant to enable exact lower limb repositioning for the subsequent clinical alignment measures. Alignment was deﬁned as the angle of intersection of the femoral and tibial mechanical axes according to the method of Sharma et al (17). To determine the mechanical axis of the femur, a line was drawn from the center of the femoral head to the center of the femoral intercondylar notch. The femoral head center was located using a series of concentric circular hip templates. A second line from 308 Hinman et al Figure 1. Determination of knee alignment using A, the calliper method (for a varus knee), B, the plumb-line method (for a varus knee), C, the inclinometer method, and D, the goniometer method. the center of the tibial spines to the center of the ankle talus established the mechanical axis of the tibia. Alignment was recorded to the nearest half degree. Varus and valgus malalignment are indicated by values ⬍180° and ⬎180°, respectively. The mechanical axis was determined by a single investigator (RSH) who was blinded to scores that were obtained with all other measures of alignment. In a sample of 14 radiographs randomly selected from the study cohort, intrarater reliability for determining mechanical axis was high (intraclass correlation coefﬁcient [ICC] 0.98). Knee joint alignment as determined by anatomic axis. Using the full-leg radiograph, the anatomic axis was determined based upon the methods of Moreland et al (22). The femoral anatomic axis was found by drawing a line from the center of the tibial spines to a point 10 cm above the tibial spines, midway between the medial and lateral femoral surfaces. For the tibial anatomic axis, a line was drawn from the center of the tibial spines to a point 10 cm below the tibial spines, midway between the medial and lateral tibial surfaces. The angle of intersection of the axes was determined by the same investigator (RSH) who found an ICC of 0.95 with this measure. Knee joint alignment as determined by clinical measures. A single investigator (RLM) blinded to radiographic measures performed 5 clinical measures of alignment in all patients (except the goniometer method, which was only performed on 26 participants). For all measures, participants stood with their weight distributed equally between the lower limbs, with knees extended to replicate positioning for mechanical alignment via radiograph. Varus malalignment was scored negatively and valgus positively. Reliability of the clinical measures was evaluated in a separate cohort of 10 participants (mean age 64 years, 5 women) with symptomatic knee OA recruited from the community prior to the study. Magee’s method. The method described by Magee (25) categorizes varus, valgus, or neutral alignment based on visual observation ( ⫽ 1 in our laboratory). Participants adducted their lower limbs slowly until either the knees or ankles touched. When the medial malleoli touched ﬁrst, the participant was classiﬁed as having varus malalignment. If the knees touched ﬁrst, the participant was classiﬁed as having valgus malalignment. If knees and ankles touched simultaneously, alignment was recorded as neutral. Calliper method. Malalignment that was evident using Magee’s method was quantiﬁed using a calliper marked in Determining Knee Alignment in OA 1-mm increments (recorded in cm to 1 decimal place) based on the methods of Cibere et al (24). In participants with varus knees, the distance between the medial knee joint lines was recorded (Figure 1A). For valgus knees, the distance between the medial malleoli was recorded. This method was found to be reliable in our laboratory (ICC 0.97). Plumb-line method. Because the calliper method is inﬂuenced by the alignment of both knee joints, a modiﬁcation of this method was used to more accurately assess alignment of the affected knee only, based on the methodology of Jonson and Gross (26). A plumb line was positioned between the lower limbs. For varus knees, the distance between the plumb line and the symptomatic medial knee joint line was measured using a calliper (recorded in cm to 1 decimal place) (Figure 1B). For valgus knees, the distance between the plumb line and the medial malleolus of the symptomatic side was measured using a calliper. This method was found to be reliable in our laboratory (ICC 0.95). Inclinometer method. This novel methodology was devised by the authors to assess orientation of the tibia with respect to the vertical. A gravity inclinometer (Acuangle, Isomed, Portland, OR) was attached to a set of callipers. Participants were positioned on the foot map, and the tibial tuberosity and neck of talus were identiﬁed. The calliper arms were placed on these landmarks (Figure 1C). The angle of the tibia with respect to the vertical (180°) was recorded. This method was found to be reliable in our laboratory (ICC 0.94). Goniometer method. Alignment determined by a standard long-arm goniometer was based on the method described by Cibere et al (24). Participants stood on the foot maps. The axis of the goniometer was positioned over the center of the patella, and the arms were aligned with the mid-thigh above the knee and with the patella tendon below the knee (Figure 1D). Angles were recorded to the nearest degree, with 180° regarded as neutral. This method was found to be reliable in our laboratory (ICC 0.84). Descriptive characteristics. Severity of pain, stiffness, and limitation in physical function were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index, a reliable and valid disease-speciﬁc questionnaire (28). Severity of OA on the radiograph was assessed using the Kellgren and Lawrence grading system, whereby 0 ⫽ normal; 1 ⫽ possible osteophytes; 2 ⫽ minimal osteophytes and possible joint space narrowing; 3 ⫽ moderate osteophytes, some narrowing, and possible sclerosis; and 4 ⫽ large osteophytes, deﬁnite narrowing, and severe sclerosis (29). Statistical analysis. Data were analyzed using the SPSS version 11.0 (SPSS, Chicago, IL). Descriptive statistics were used for participant characteristics and scores obtained on all alignment measures. Correlations between mechanical alignment and the tested alignment methods were determined using Pearson’s correlation coefﬁcients, excluding the Magee method, which was analyzed using Spearman’s rho. Simple linear regression was used to de- 309 velop regression equations for statistically signiﬁcant relationships (excluding the Magee method). Correlation coefﬁcients of 0.5– 0.75 were regarded as good, and values ⬎0.75 were regarded as excellent (30). P values less than 0.05 were regarded as signiﬁcant. RESULTS Participant characteristics are presented in Table 1. The cohort comprised more women than men. Participants were generally overweight (31) and reported moderate levels of pain, stiffness, and physical limitation. A range of radiographic severity was evident, with the majority (68%) of participants demonstrating moderate-severe changes on radiograph (grade 3 or 4). Thirty-six (90%) participants had a varus mechanical axis, 3 were valgus (8%), and 1 was neutral (2%). The entire cohort demonstrated a mean varus malalignment of 5.8° from the neutral position, based on the mechanical axis on radiograph. Alignment characteristics of the cohort according to each measurement technique utilized are presented in Table 2. There was an excellent correlation between the anatomic axis and the mechanical axis (r ⫽ 0.88, P ⬍ 0.001) (Figure 2). Regression analysis deﬁned this relationship according to the following equation: mechanical axis ⫽ 0.915(anatomic axis) ⫹ 13.895. The anatomic axis accounted for 77% of the total variance in mechanical axis scores. Of the 5 clinical measures, the inclinometer method demonstrated the strongest correlation with the mechanical axis, with a correlation coefﬁcient of 0.80 (P ⬍ 0.001) (Figure 3). Regression analysis deﬁned this relationship with the following equation: mechanical axis ⫽ 1.153(inclinometer angle) ⫺ 28.716. The inclinometer angle accounted for 64% of the total variability in mechanical axis Table 1. Participant characteristics* Characteristic Value Age, years Height, meters Weight, kg Body mass index, kg/m2 Reported symptom duration, years WOMAC score† Pain subsection Stiffness subsection Physical function subsection Sex, male:female Osteoarthritis severity, no.‡ Grade 1 Grade 2 Grade 3 Grade 4 64.7 ⫾ 9.4 1.64 ⫾ 0.09 79.1 ⫾ 12.0 29.6 ⫾ 4.2 8.8 ⫾ 7.9 9⫾3 4⫾1 30 ⫾ 11 16:24 3 10 11 16 * Values are the mean ⫾ SD unless otherwise indicated. WOMAC ⫽ Western Ontario and McMaster Universities Osteoarthritis Index. † Score range includes pain (0 –20), stiffness (0 – 8), and physical function (0 – 68). Higher scores indicate worse symptoms. ‡ Radiographic severity according to Kellgren and Lawrence grading system, where higher grades indicate more severe disease. 310 Hinman et al Table 2. Alignment characteristics of the cohort according to each measurement procedure* Method Value Mechanical axis, °† Anatomic axis, °† Calliper method, cm† Plumb-line method, cm† Inclinometer, °† Goniometer, °† Magee’s method, no. (%) Varus Valgus Neutral 174.2 ⫾ 4.9 (164.5–186.0) 175.2 ⫾ 4.7 (166.0–185.5) ⫺0.8 ⫾ 3.5 (⫺7.6–7.5) ⫺0.4 ⫾ 1.9 (⫺3.3–3.9) 176 ⫾ 3 (169–182) 180 ⫾ 6 (167–192) 25 (63) 13 (33) 2 (4) * Values are the mean ⫾ SD (range) unless otherwise indicated. † Lower values represent a more varus knee alignment. Figure 3. Scatterplot depicting the relationship between the inclinometer and the mechanical axis (n ⫽ 40). The mechanical axis, as determined by the full-leg radiograph, is regarded as the gold standard for measuring knee joint alignment in the frontal plane. This study evaluated the criterion-related validity of 6 alternative measures for assessing malalignment, as compared with the mechanical axis. An alternative radiographic measure, the anatomic axis, was tested, as were 5 clinical measures of alignment (the Magee, calliper, plumb-line, inclinometer, and goniometer methods). Not surprisingly, the anatomic axis best correlated with the mechanical axis, accounting for 77% of the total variance in mechanical axis score. Importantly, 2 clinical measures were shown to be valid indicators of the mechanical axis, namely the inclinometer and calliper methods. Although the plumb-line and Magee methods correlated signiﬁcantly with the mechanical axis, these relationships were weaker than those demonstrated by the former clinical methods. The goniometer method used in this study was not found to be a valid measure of mechanical axis. Participants in this study were symptomatic and demonstrated medial tibiofemoral joint osteophytes. The authors believe the study cohort accurately reﬂects the wider knee OA population given the predominance of women in the sample, the fact that participants were generally overweight with moderately severe symptoms, and the wide range of radiographic severity of disease that was evident. The study sample demonstrated a mean mechanical axis of 174.2°, indicating an average varus malalignment of 5.8°. This is greater than that of healthy individuals who generally demonstrate only a slight varus angulation of 1–2° (21,22,32). These ﬁndings are in agreement with other studies involving knee OA participants. Miyazaki et al (33) reported a mean varus malalignment of 6.5° in their sam- Figure 2. Scatterplot depicting the relationship between the anatomic axis and mechanical axis (n ⫽ 40). Figure 4. Scatterplot depicting the relationship between the calliper method and the mechanical axis (n ⫽ 40). scores. An excellent correlation with the mechanical axis was also observed for the calliper method (r ⫽ 0.76, P ⬍ 0.001) (Figure 4), which accounted for 58% of the total variation in mechanical axis score. The relationship between the calliper reading and the mechanical axis was deﬁned with the following equation: mechanical axis ⫽ 1.049(calliper reading) ⫹ 175.049. A good correlation was evident between the mechanical axis and the plumb-line method (r ⫽ 0.71, P ⬍ 0.001) (Figure 5), generating a relationship deﬁned with the following equation: mechanical axis ⫽ 1.803(plumb-line score) ⫹ 175.006. The plumbline method accounted for 50% of total variance in mechanical axis. In contrast, Magee’s method (visual observation) was found to have a weaker, although still statistically signiﬁcant, relationship with the mechanical axis (r ⫽ ⫺0.52, P ⫽ 0.001), accounting for only 27% of the total variability in mechanical axis. No relationship was observed between the goniometer method and the mechanical axis (r ⫽ 0.32, P ⫽ 0.12) (Figure 6). DISCUSSION Determining Knee Alignment in OA Figure 5. Scatterplot depicting the relationship between the plumb-line method and the mechanical axis (n ⫽ 40). ple of 106 patients with medial knee OA, Sharma et al (34) reported a mean varus malalignment of 5.1° in their group of 236 patients with tibiofemoral OA, and Cooke et al (32) reported a mean varus angulation of 3.95° in their 167 participants with symptomatic OA. Few studies have investigated the validity of methods for measuring knee alignment in patients with knee OA. One study, reported in abstract form, also compared the anatomic axis and a goniometer method with the mechanical axis in a cohort with symptomatic knee OA (23). In contrast to the present study, anatomic axis was measured using a semiﬂexed knee radiograph. Similar to the present ﬁndings, the authors demonstrated a signiﬁcant correlation between the anatomic and mechanical axes (r ⫽ 0.74). In comparison, the present study revealed a much stronger correlation between anatomic and mechanical axes on the full-leg radiograph (r ⫽ 0.88), which is probably due to the fact that the lower-limb position on radiograph was identical for the calculation of each angular measure. Predictive validity of the anatomic axis on an extended-knee radiograph has previously been demonstrated by Cicuttini et al (18) who demonstrated that baseline anatomic axis was correlated with change in cartilage volume over time. The goniometer method utilized by McDaniel et al (23) was also slightly different from that used in the present study. The lower goniometer arm was positioned along the tibial shaft, in contrast to the present study, which aligned the arm with the patellar tendon (selected because of the high reliability reported with this method in knee OA ). Whereas McDaniel et al (23) reported a strong corre- Figure 6. Scatterplot depicting the relationship between the goniometer method and the mechanical axis (n ⫽ 26). 311 lation between their goniometer method and the mechanical axis (r ⫽ 0.72), we were unable to demonstrate a signiﬁcant correlation using the present methodology (r ⫽ 0.32). During data collection, it was observed that the patellar tendon did not always align with the tibial shaft. One possible explanation for this phenomenon may be the presence of patellar subluxation (35), which may alter the angle of the patellar tendon with respect to the tibial shaft, thus generating goniometer scores that do not accurately reﬂect underlying skeletal alignment. Results of this study demonstrated that both the inclinometer and calliper methods are valid measures of alignment in knee OA. A novel methodology using a gravity inclinometer was devised by the authors based on the assumption that tibial alignment with respect to the vertical reﬂects the tibial mechanical axis. Obtained results (r ⫽ 0.80) appear to support this assumption. The calliper method was also observed to be a valid measure of the mechanical axis. This method has been reported with respect to knee OA in terms of its reliability (24) but not validity; therefore, comparison of the present ﬁndings with others is not possible. Compared with the inclinometer and calliper methods, the plumb-line and Magee methods were not as valid for the measurement of knee alignment. These latter methods have been reported as reliable in young healthy individuals (26), but to the authors’ knowledge, they have not previously been validated in any population. The somewhat more complex setup for the plumb-line measure, which allows greater capacity for measurement error, probably accounts for this method’s slightly poorer validity compared with the more simple calliper method. Magee’s method is dependent upon the patient and investigator accurately identifying the ﬁrst point of soft tissue contact between either the medial malleoli or the medial knees. Excess soft tissue at the medial knee may lead to a false classiﬁcation of valgus malalignment, even though the underlying skeletal structure may indicate a varus malalignment. There are several limitations to this study. Due to the differing soft tissue properties across the lower limb from the hip to the ankle, a graduated-grid cassette is advocated for full-leg radiographs to ensure clarity of image (22). The 35.6 ⫻ 91.4 – cm graduated-grid cassette available for use in this study was adequate for shorter participants but not for their taller counterparts. Unfortunately, a longer graduated-grid cassette was not available, therefore taller participants underwent radiography using a nongraduated cassette. Although all radiographs of taller participants were carefully monitored for image clarity, it is possible that mechanical axes determined from these ﬁlms may not have been as accurate as those determined for shorter participants. The general unavailability of sufﬁciently long graduated-grid cassettes further supports the need for alternative measures of knee alignment, such as the anatomic axis, which requires only a standard nongraduated cassette to image the knee joint. Only 3 participants demonstrated valgus mechanical malalignment, probably because the selection criteria were biased towards medial tibiofemoral joint OA. Therefore, the present ﬁndings pertain primarily to the validity of methods for measuring varus malalignment. It is unlikely that results should differ 312 for valgus malalignment; however, future research should focus on evaluating the validity of the anatomic axis, the inclinometer, and calliper methods for patients with knee OA with valgus malalignment. The ﬁndings in this study have important clinical implications. Several alternative methods for evaluating frontal plane knee alignment in OA have been identiﬁed, including the use of an extended anteroposterior knee radiograph (which allows visualization of the lower limb 10 cm above and below the knee), an inclinometer, or callipers. Advantages of the knee radiograph over the the full-leg radiograph, which is the gold standard method, include reduced cost to the patient, researcher, and/or health care system; reduced exposure of the patient to ionizing radiation (particularly around the pelvis); and no problem with lack of a long graduated-grid cassette hampering determination of bony landmarks. The knee radiograph forms part of the standard radiographic examination for knee OA, therefore extra radiographs just to determine knee alignment are not needed. Unfortunately, calculation of alignment from the knee radiograph is just as cumbersome and time consuming as that from a full-leg radiograph, requiring the clinician/researcher to carefully locate 4 bony landmarks, draw lines to identify the tibial and femoral axes, and ﬁnally measure the angle of intersection between the axes. In contrast to radiographic methods, the inclinometer and calliper methods of measuring alignment generate instant results, are quick to administer, are inexpensive (involving no cost to the patient/health care system and only a small outlay by the clinician/researcher to purchase the equipment required initially), and do not expose the patient to radiation. The inclinometer offers advantages over the calliper method because it is less likely to be adversely inﬂuenced by soft tissue characteristics of the lower limb, hence its slightly greater correlation with the mechanical axis. However, there is a greater risk of misclassiﬁcation when using these clinical measures of alignment rather than the anatomic axis, given the lower correlation observed with the mechanical axis (0.76 – 0.80 versus 0.88). Further studies are needed to determine whether signiﬁcant misclassiﬁcation does in fact occur, and to determine its consequences. Clinical measures of alignment are probably no substitute for radiographic measures in surgical procedures where precise measures of frontal plane malalignment are required for optimal outcome. In conclusion, this study demonstrated that the anatomic axis, inclinometer, and callipers are valid measures of determining knee alignment in OA. Clinically, such methods may increase assessment by clinicians and researchers of this important parameter in patients with knee OA. Future research should evaluate the predictive validity of the clinical measures with regard to disease progression and functional decline over time. ACKNOWLEDGMENTS The authors would like to thank Tim Wrigley for his technical input, Ben Metcalf and Georgie Kemp for their assistance with data collection, and Phil Wood and the radiol- Hinman et al ogy staff at Royal Melbourne Hospital for their help with the radiographs. REFERENCES 1. Felson DT, Naimark A, Anderson J, Kazis L, Castelli W, Meenan RF. The prevalence of knee osteoarthritis in the elderly: The Framingham Osteoarthritis Study. Arthritis Rheum 1987;30:914 – 8. 2. Hassan BS, Mockett S, Doherty M. Static postural sway, proprioception, and maximal voluntary quadriceps contraction in patients with knee osteoarthritis and normal control subjects. Ann Rheum Dis 2001;60:612– 8. 3. Messier SP, Loeser RF, Hoover JL, Semble EL, Wise CM. Osteoarthritis of the knee: effects on gait, strength, and ﬂexibility [published erratum appears in Arch Phys Med Rehabil 1992;73:252]. Arch Phys Med Rehabil 1992;73:29 –36. 4. O’Reilly SC, Jones A, Muir KR, Doherty M. Quadriceps weakness in knee osteoarthritis: the effect on pain and disability. Ann Rheum Dis 1998;57:588 –94. 5. Sharma L. Proprioceptive impairment in knee osteoarthritis. Rheum Dis Clin North Am 1999;25:299 –314. 6. Sharma L, Lou C, Felson DT, Dunlop DD, Kirwan-Mellis G, Hayes KW, et al. Laxity in healthy and osteoarthritic knees. Arthritis Rheum 1999;42:861–70. 7. Jordan KM, Arden NK, Doherty M, Bannwarth B, Bijlsma JW, Dieppe P, et al. EULAR recommendations 2003: an evidence based approach to the management of knee osteoarthritis: report of a task force of the Standing Committee for International Clinical Studies Including Therapeutic Trials (ESCISIT). Ann Rheum Dis 2003;62:1145–55. 8. American College of Rheumatology Subcommittee on Osteoarthritis Guidelines. Recommendations for the medical management of osteoarthritis of the hip and knee: 2000 update. Arthritis Rheum 2000;43:1905–15. 9. Cahue S, Dunlop D, Hayes K, Song J, Torres L, Sharma L. Varus–valgus alignment in the progression of patellofemoral osteoarthritis. Arthritis Rheum 2004;50:2184 –90. 10. Cooke TD, Li J, Scudamore RA. Radiographic assessment of bony contributions to knee deformity. Orthop Clin North Am 1994;25:387–93. 11. Felson DT, Goggins J, Niu J, Zhang Y, Hunter DJ. The effect of body weight on progression of knee osteoarthritis is dependent on alignment. Arthritis Rheum 2004;50:3904 –9. 12. Ledingham J, Regan M, Jones A, Doherty M. Radiographic patterns and associations of osteoarthritis of the knee in patients referred to hospital. Ann Rheum Dis 1993;52:520 – 6. 13. McAlindon TE, Snow S, Cooper C, Dieppe PA. Radiographic patterns of osteoarthritis of the knee joint in the community: the importance of the patellofemoral joint. Ann Rheum Dis 1992;51:844 –9. 14. Schipplein OD, Andriacchi TP. Interaction between active and passive knee stabilizers during level walking. J Orthop Res 1991;9:113–9. 15. Creamer P, Hochberg MC. Osteoarthritis. Lancet 1997;350: 503– 8. 16. Cooper C, Snow S, McAlindon TE, Kellingray S, Stuart B, Coggon D, et al. Risk factors for the incidence and progression of radiographic knee osteoarthritis. Arthritis Rheum 2000;43: 995–1000. 17. Sharma L, Song J, Felson DT, Cahue S, Shamiyeh E, Dunlop DD. The role of knee alignment in disease progression and functional decline in knee osteoarthritis [published erratum appears in JAMA 2001;286:792]. JAMA 2001;286:188 –95. 18. Cicuttini F, Wluka A, Hankin J, Wang Y. Longitudinal study of the relationship between knee angle and tibiofemoral cartilage volume in subjects with knee osteoarthritis. Rheumatology (Oxford) 2004;43:321– 4. 19. Ritter MA, Faris PM, Keating EM, Meding JB. Postoperative alignment of total knee replacement: its effect on survival. Clin Orthop Relat Res 1994;299:153– 6. 20. Yasuda K, Majima T, Tsuchida T, Kaneda K. A ten- to 15-year follow-up observation of high tibial osteotomy in medial com- Determining Knee Alignment in OA 21. 22. 23. 24. 25. 26. 27. 28. partment osteoarthrosis. Clin Orthop Relat Res 1992;282:186 – 95. Hsu RW, Himeno S, Coventry MB, Chao EY. Normal axial alignment of the lower extremity and load-bearing distribution at the knee. Clin Orthop Relat Res 1990;255:215–27. Moreland JR, Bassett LW, Hanker GJ. Radiographic analysis of the axial alignment of the lower extremity. J Bone Joint Surg Am 1987;69:745–9. McDaniel GE, Vail TP, Kraus VB. Comparison of knee alignment angle by x-ray and goniometer [abstract]. Arthritis Rheum 2004;50 Suppl 9:S343. Cibere J, Bellamy N, Thorne A, Esdaile JM, McGorm KJ, Chalmers A, et al. Reliability of the knee examination in osteoarthritis: effect of standardization. Arthritis Rheum 2004;50:458 – 68. Magee D. Orthopedic physical assessment. 2nd ed. Philadelphia: W.B. Saunders; 1992. Jonson SR, Gross MT. Intraexaminer reliability, interexaminer reliability, and mean values for nine lower extremity skeletal measures in healthy naval midshipmen. J Orthop Sports Phys Ther 1997;25:253– 63. Altman R, Asch E, Bloch D, Bole G, Borenstein D, Brandt K, et al. Development of criteria for the classiﬁcation and reporting of osteoarthritis: classiﬁcation of osteoarthritis of the knee. Arthritis Rheum 1986;29:1039 – 49. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health status instrument 313 29. 30. 31. 32. 33. 34. 35. for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833– 40. Kellgren JH, Lawrence JS. Radiological assessment of osteoarthrosis. Ann Rheum Dis 1957;16:494 –502. Portney L, Watkins M. Foundations of clinical research: applications to practice. 2nd ed. Upper Saddle River (NJ): Prentice Hall Health; 2000. National Health and Medical Research Council. Dietary guidelines for older Australians. Canberra: Commonwealth of Australia; 1999. p. 1– 40. Cooke D, Scudamore A, Li J, Wyss U, Bryant T, Costigan P. Axial lower-limb alignment: comparison of knee geometry in normal volunteers and osteoarthritis patients. Osteoarthritis Cartilage 1997;5:39 – 47. Miyazaki T, Wada M, Kawahara H, Sato M, Baba H, Shimada S. Dynamic load at baseline can predict radiographic disease progression in medial compartment knee osteoarthritis. Ann Rheum Dis 2002;61:617–22. Sharma L, Cahue S, Song J, Hayes K, Pai YC, Dunlop D. Physical functioning over three years in knee osteoarthritis: role of psychosocial, local mechanical, and neuromuscular factors. Arthritis Rheum 2003;48:3359 –70. Harrison MM, Cooke TD, Fisher SB, Grifﬁn MP. Patterns of knee arthrosis and patellar subluxation. Clin Orthop Relat Res 1994;309:56 – 63.