~
Arthritis & Rheumatism Official Journal of t h e American College of Rheumatology
RELATIONSHIP BETWEEN ARTHROSCOPIC EVIDENCE OF CARTILAGE DAMAGE AND RADIOGRAPHIC EVIDENCE OF JOINT SPACE NARROWING IN EARLY OSTEOARTHRITIS OF THE KNEE ROSE S. FIFE, KENNETH D. BRANDT, ETHAN M. BRAUNSTEIN, BARRY P. KATZ, K. DONALD SHELBOURNE, LORRIE A. KALASINSKI, and SARAH RYAN We examined the relationship between articular cartilage degeneration, as visualized arthroscopically,
the presence of medial compartment articular cartilage degeneration was 0.61, i.e., only 61% of patients with
and joint space narrowing (JSN) in standing anteropos.
normal (grade 0) medial compartment cartilage had a normal medial joint space. Of 22 patients with >50%
terior knee radiographs of 161 patients with chronic
medial JSN, 9 (41%) had normal articular cartilage in the medial compartment at arthroscopy. Of 6 patients with >SO% lateral JSN, 3 (50%) had normal lateral compartment articular cartilage at arthroscopy. Among 36 patients with >25% JSN who had neither medial nor lateral compartment articular cartilage degeneration, JSN was associated with articular cartilage degeneration in the patellofemoral compartment in 8 (22%), with meniscus degeneration in 18 (50%), and with both in 8 (22%). Thus, in these patients with chronic knee pain, radiographic evidence of JSN in the tibiofemoral compartment did not permit confident prediction of the status of the articular cartilage.
knee pain. The majority of these patients had radiographic findings of mild osteoarthritis. Twenty-five (33%) of the 76 patients in the series whose radiographs showed tibiofemoral JSN had grossly normal articular cartilage in both tibiofemoral compartments at arthroscopy (false-positive). The specificity of medial JSN for From the Indiana University School of Medicine, the Specialized Center of Research in Osteoarthritis, and the Multipurpose Arthritis Center, and the Sports Medicine Clinic, Methodist Hospital of Indianapolis, Indianapolis, Indiana. Supported in part by NIH grants AR-20582, AR-39250, and AR-7448, and by awards from the Arthritis Foundation and the Grace M. Showalter Trust. Dr. Fife is the recipient of an Arthritis Foundation Biomedical Research Grant. Rose S . Fife, MD: Associate Professor of Medicine and Biochemistry and Molecular Biology, Indiana University School of Medicine: Kenneth D. Brandt, MD: Professor of Medicine and Head, Rheumatology Division, Indiana University School of Medicine, Director, Indiana University Specialized Center of Research in Osteoarthritis, and Director, Indiana University Multipurpose Arthritis Center: Ethan M. Braunstein, MD: Professor of Radiology, lndiana University School of Medicine: Barry P. Katz, PhD: Associate Professor of Medicine, Indiana University School of Medicine; K. Donald Shelbourne, MD: Staff Orthopaedic Surgeon, Sports Medicine Clinic, Methodist Hospital of Indianapolis: Lorrie A. Kalasinski, MPH: Applied Statistician, Indiana University Specialized Center of Research in Osteoarthritis: Sarah Ryan, RN, MSN: Rheumatology Division, Indiana University School of Medicine. Address reprint requests to Rose S. Fife, MD, Rheumatology Division, Indiana University School of Medicine, 541 Clinical Drive, Indianapolis, IN 46202. Submitted for publication May 29, 1990: accepted in revised form October 12, 1990.
Pain is the clinical feature that leads most patients with osteoarthritis (OA) to seek medical attention. Although the pathologic hallmark of OA is loss of articular cartilage, since the cartilage has no nerve supply, the pain in OA arises only after secondary involvement of other structures, e.g., subchondral bone, synovium, or muscle (1). Thus, by the time the patient with OA presents to the physician, articular cartilage breakdown is often far advanced. No practical, reproducible, noninvasive method exists at present for the detection of early articular cartilage loss in OA. Imaging techniques, such as magnetic resonance imaging (2) and ultrasonography (3), have not proved to be sensitive or to produce
Arthritis and Rheumatism, Vol. 34, No. 4 (April 1991)
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FIFE ET AL
378
sufficiently reproducible results for detection of “pre-
clinical” OA. Similarly, efforts to develop a serologic “marker” of OA for this purpose have not yet been successful (4-6). Therefore, radiography, although insensitive in detecting early OA and in monitoring disease progression, remains a mainstay in diagnosis and management of OA (7,8). It has been shown that an anteroposterior knee radiograph taken while the subject is standing more accurately reflects joint space narrowing (JSN) than does a knee radiograph obtained with the subject supine (9-1 1). Notably, the radiographic grading scale most widely employed today, the KellgredLawrence scale (8,12), wa s developed prior to the demonstration that a standing knee radiograph is more sensitive for assessment of JSN than a radiograph taken when the patient is supine. Furthermore, the KellgredLawrence radiographic criteria permit the diagnosis of definite OA in the presence of osteophytosis alone, without JSN. However, loss of articular cartilage, not osteophytosis, is the predominant pathologic feature of OA. Indeed, in the absence of JSN or bony changes, osteophytosis may be due to aging, and not to OA (13-15). We undertook the present study t o examine the specificity of JSN, as demonstrated in the standing knee radiograph, for articular cartilage changes of OA. The results in this series of patients, which consisted predominantly of patients with radiographic evidence of relatively “early” or “mild” OA, indicate that “false-positive” radiographic evidence of articular cartilage loss, i.e., JSN in the absence of articular cartilage damage, was common.
PATIENTS AND METHODS Patient selection. The study subjects consisted of 161 consecutive patients undergoing arthroscopy at a sports medicine practice, for evaluation of chronic knee pain. A small number of these patients were included in a previous study of a serologic marker for OA (4). Patients with known inflammatory arthritis, e.g., rheumatoid arthritis or gout, were excluded from analysis, and patients were included in the study only if a standing anteroposterior knee radiograph had been obtained shortly before arthroscopy. All radiographs were performed in the same facility by the same staff of 2 technicians, using consistent standardized techniques (cassette posterior to the knee; beam aimed at the midpoint of the patella; distance from tube to film 40”). Standing radiographs were obtained with the patient standing on both feet, with hidher knees in as full extension as possible for the individual. Lateral knee radiographs were obtained with the patient in a supine position.
Arthroscopic grading of OA. At the time of arthroscopy, the severity of the defects visible on each of 6 articular surfaces (medial and lateral femoral condyles, medial and lateral tibial plateaus, patellar surface, and trochlear groove) was graded as follows (16): grade 0 = no defect; grade 1 = superficial erosion(s); grade 2 = partial-thickness erosion(s) 2.5 cm2; and grade 4 = full-thickness erosion(s). The status of the menisci also was evaluated. Radiographic analyses. Lateral and standing anteroposterior radiographs of the knees were evaluated and graded by an experienced skeletal radiologist (EMB). A judgment concerning the degree of JSN as seen in the anteroposterior radiograph was made by comparing medial and lateral compartments of the same knee, and the right and left knee of each patient. If both compartments or both knees were abnormal, a knee radiograph from a normal subject of the same sex was used for comparison. The effects of beam position and of knee flexion on the width of the joint spaces were examined using knee radiographs of a normal volunteer. The medial and lateral joint spaces were measured using a perpendicular line drawn between the most distal aspect of the cortex of the condyle and the cortex of the adjacent tibial plateau. The radiographic severity of OA was graded according to the scale of Kellgren and Lawrence (8,12), where grade 0 = normal; grade I = doubtful narrowing of joint space and possible osteophytic lipping; grade I1 = definite osteophytes and possible narrowing of joint space; grade 111 = moderate multiple osteophytes, definite narrowing of joint space, some sclerosis, and possible deformity of bone contour; and grade IV = large osteophytes, marked narrowing of joint space, severe sclerosis, and definite deformity of bone contour. Statistical analysis. Sensitivity, specificity, and predictive value of the standing knee radiograph for the detection of OA were calculated, using the arthroscopic findings as the “gold standard.” Medial, lateral, and patellofemoral compartments were examined separately. Data for medial and lateral compartment JSN were further stratified based on the presence or absence of meniscal abnormalities. Sensitivity was calculated as the proportion of patients with cartilage changes of OA (based on arthroscopy) who were classified as having JSN by radiography. Specificity was calculated as the proportion of patients with no arthroscopic evidence of articular cartilage damage who were classified as having no JSN by radiography. The positive predictive value is the probability that those who were classified as having JSN by the radiographic criteria actually had OA by arthroscopy. The negative predictive value is the probability that those classified as normal (i.e., no JSN) by the radiographic criteria had normal articular cartilage at arthroscopy.
RESULTS One hundred thirty-four of the 161 patients studied were male, reflecting the fact that the subjects were derived from a sports medicine practice. The
379
RELATIONSHIP OF JSN TO SEVERITY OF KNEE OA
mean k SD age of the entire group was 36.4 ? 12.9 years, with a range of 12-69 years. In 13 patients, meniscectomy had previously been performed in the involved knee (8 medial, 4 lateral, 1 both menisci). Radiographs of 83 of the 161 patients (52%) were scored as grade 0 or I according to the Kellgrenl Lawrence criteria for OA severity, while 55 (34%) were scored as grade 11; only 14% of the patients had radiographically severe OA (grade III or IV). Tibiofemoral JSN. Radiographs of 76 patients showed >25% JSN in either or both tibiofemoral compartments. Twenty-five (33%) of these patients had grossly normal articular cartilage in both tibiofemoral compartments at arthroscopy (radiographic “false-positive’’ findings). Medial compartment. Of the 113 patients with no medial compartment articular cartilage degeneration at arthroscopy (grade 0), 44 (39%) had >25% medial JSN by radiography (“false-positive”) (Table 1). Nine of these patients (8%) had >50% JSN. Conversely, of the 38 patients with grade 2 4 medial compartment AC changes at arthroscopy, 11 (29%) did not have medial JSN by radiography and were considered to be radiographically “false-negative.’’ Based on the above results, the sensitivity of medial JSN for the diagnosis of grade 2-4 medial compartment articular cartilage changes at arthroscopy was 0.71. For the diagnosis of medial compartment articular cartilage degeneration of any degree (i.e., grade 1-4), the sensitivity of medial JSN was 0.67. The specificity of medial JSN for the presence of medial compartment articular cartilage degeneration was 0.61, i.e., 61% of the patients with normal (grade 0) medial compartment cartilage did not have medial JSN radiographically. The positive predictive value of medial JSN for Table 1. Relationship of medial joint space narrowing to medial Compartment cartilage degeneration at arthroscopy
Arthroscopic grade of cartilage degeneration*
Severity of radiographic joint space narrowing* None t 69
5 25 88 18
25-50%
>50%
3% 4t 0 12 3
* See Patients and Methods for explanation of grading scales. ‘t Joint space narrowing SO%
10 t 0 1 2 3
3t 0 0 I 2
* See Patients and Methods for explanation of grading scales. t Joint space narrowing 25% medial JSN had significant medial compartment articular cartilage changes at arthroscopy. When any medial compartment articular cartilage changes (grade 1-4) were present at arthroscopy, the positive predictive value of medial JSN was 0.42. Eighty-five patients were judged not to have medial JSN by radiography; of these, 69 (81%) had normal medial compartment articular cartilage at arthroscopy, while another 5 exhibited only grade 1 changes. Hence, the negative predictive value, i.e., the likelihood that a patient with no medial JSN would have essentially normal medial compartment articular cartilage (i.e., grade 0 or l), was 0.87. Lateral compartment. Thirteen of the 128 patients (10%) with normal lateral compartment articular cartilage at arthroscopy (grade 0) had >25% lateral JSN; 3 of these patients had >50% JSN. Conversely, 15 of the 24 patients (63%) with advanced arthroscopic changes in the lateral compartment, i.e., grades 2 4 , did not have lateral JSN (Table 2). Thus, the sensitivity of lateral JSN for grade 1-4 OA was 0.27, and for grade 2-4 OA it was only 0.38-much poorer than that for medial JSN; its specificity was 0.90-much higher than that for medial JSN. The positive predictive value of lateral JSN for grades 2-4 OA was 0.41 and the negative predictive value was 0.89, similar to the findings for medial JSN. Patellofemoral compartment. In 17 patients, arthroscopic evidence of articular cartilage degeneration was confined to the patella or the trochlear groove. Of these, 7 exhibited >25% medial compartment JSN, while 5 had >25% JSN in both compartments.
FIFE ET AL
380 Table 3. Medial compartment arthroscopic findings and radiographic joint space narrowing in patients with a tear or degeneration of the medial meniscus
Severity of medial compartment joint space narrowing*
Arthroscopic grade of OA in medial compartment*
Nonet
25-50%
>50%
0 1 2 3 4
32 2 1 6 0
17 2 0 8 2
3 1 0 3 2
* See Patients and Methods for explanation of grading scales. OA osteoarthritis. i Joint space narrowing 25% medial JSN (Table 3). This subgroup accounted for 26% of all patients in the series with >25% medial JSN. Of the 128 patients who had normal lateral compartment articular cartilage at arthroscopy (grade 0), gross lateral meniscal abnormalities were observed arthroscopically in 24 (19%). Four (17%) exhibited >25% lateral JSN (Table 4). These individuals represented 18% of all patients with >25% lateral JSN in this series. JSN with normal tibiofemoral articular cartilage. Thirty-six (47%) of the 76 patients in the series who had >25% JSN had normal tibiofemoral compartment cartilage at arthroscopy. JSN was associated with articular cartilage degeneration in the patellofemoral compartment in 8 of these patients, with meniscal degeneration in 18, and with both in 8. Effects of knee flexion and beam position. Radiographs of a normal knee revealed a progressive loss in the width of the medial compartment joint space with
flexion. Thus, with 0" of flexion, the joint space measured 6.0 mm; with lo" of flexion, it was 4.5 mm, a decrease of 25%. The lateral compartment joint space, which was 7.0 mm when the knee was in the neutral position, was only 5.0 mm when the knee was flexed to lo", a decrease of 29%. Similarly, when the x-ray beam was directed 1 cm below the midpoint of the patella, the width of the medial joint space of the normal knee was 17% less than when the beam was centered at the midpoint of the patella. When the beam was aimed 0.5 cm above the midpoint of the patella, the width of the medial joint space was -8% less than when it was centered.
DISCUSSION The majority of the patients in the present study had early OA based on radiographic criteria, and, since they were derived from a sports medicine clinic, the patient population was somewhat younger than most reported series of OA patients. The importance of the present study is that it permitted comparison of radiographic JSN with the anatomic changes in articular cartilage seen at arthroscopy, Our results indicate that the correlation between articular cartilage loss and tibiofemoral JSN is poor. In all but 2 of the 36 patients with >25% JSN who had no evidence of tibiofemoral articular cartilage degeneration, JSN was associated with degeneration of the patellofemoral compartment, of a meniscus, or both. The KellgredLawrence criteria, which are widely used for grading the severity of knee OA, were derived from analyses of knee radiographs obtained with the patients in a supine position, and with these criteria, the diagnosis of definite OA can be made when osteophytes are the only radiographic abnormalTable 4. Lateral compartment arthroscopic findings and radiographic joint space narrowing in patients with a tear or degeneration of the lateral meniscus
Arthroscopic grade of OA in lateral compartment*
Severity of lateral compartment joint space narrowing* Nonet
25-50%
>50%
20 0 2 4 0
3 0 1
1 0 0 1 2
1 0
* See Patients and Methods for explanation of grading scales. OA osteoarthritis. t Joint space narrowing
Arthritis & Rheumatism Official Journal of t h e American College of Rheumatology
RELATIONSHIP BETWEEN ARTHROSCOPIC EVIDENCE OF CARTILAGE DAMAGE AND RADIOGRAPHIC EVIDENCE OF JOINT SPACE NARROWING IN EARLY OSTEOARTHRITIS OF THE KNEE ROSE S. FIFE, KENNETH D. BRANDT, ETHAN M. BRAUNSTEIN, BARRY P. KATZ, K. DONALD SHELBOURNE, LORRIE A. KALASINSKI, and SARAH RYAN We examined the relationship between articular cartilage degeneration, as visualized arthroscopically,
the presence of medial compartment articular cartilage degeneration was 0.61, i.e., only 61% of patients with
and joint space narrowing (JSN) in standing anteropos.
normal (grade 0) medial compartment cartilage had a normal medial joint space. Of 22 patients with >50%
terior knee radiographs of 161 patients with chronic
medial JSN, 9 (41%) had normal articular cartilage in the medial compartment at arthroscopy. Of 6 patients with >SO% lateral JSN, 3 (50%) had normal lateral compartment articular cartilage at arthroscopy. Among 36 patients with >25% JSN who had neither medial nor lateral compartment articular cartilage degeneration, JSN was associated with articular cartilage degeneration in the patellofemoral compartment in 8 (22%), with meniscus degeneration in 18 (50%), and with both in 8 (22%). Thus, in these patients with chronic knee pain, radiographic evidence of JSN in the tibiofemoral compartment did not permit confident prediction of the status of the articular cartilage.
knee pain. The majority of these patients had radiographic findings of mild osteoarthritis. Twenty-five (33%) of the 76 patients in the series whose radiographs showed tibiofemoral JSN had grossly normal articular cartilage in both tibiofemoral compartments at arthroscopy (false-positive). The specificity of medial JSN for From the Indiana University School of Medicine, the Specialized Center of Research in Osteoarthritis, and the Multipurpose Arthritis Center, and the Sports Medicine Clinic, Methodist Hospital of Indianapolis, Indianapolis, Indiana. Supported in part by NIH grants AR-20582, AR-39250, and AR-7448, and by awards from the Arthritis Foundation and the Grace M. Showalter Trust. Dr. Fife is the recipient of an Arthritis Foundation Biomedical Research Grant. Rose S . Fife, MD: Associate Professor of Medicine and Biochemistry and Molecular Biology, Indiana University School of Medicine: Kenneth D. Brandt, MD: Professor of Medicine and Head, Rheumatology Division, Indiana University School of Medicine, Director, Indiana University Specialized Center of Research in Osteoarthritis, and Director, Indiana University Multipurpose Arthritis Center: Ethan M. Braunstein, MD: Professor of Radiology, lndiana University School of Medicine: Barry P. Katz, PhD: Associate Professor of Medicine, Indiana University School of Medicine; K. Donald Shelbourne, MD: Staff Orthopaedic Surgeon, Sports Medicine Clinic, Methodist Hospital of Indianapolis: Lorrie A. Kalasinski, MPH: Applied Statistician, Indiana University Specialized Center of Research in Osteoarthritis: Sarah Ryan, RN, MSN: Rheumatology Division, Indiana University School of Medicine. Address reprint requests to Rose S. Fife, MD, Rheumatology Division, Indiana University School of Medicine, 541 Clinical Drive, Indianapolis, IN 46202. Submitted for publication May 29, 1990: accepted in revised form October 12, 1990.
Pain is the clinical feature that leads most patients with osteoarthritis (OA) to seek medical attention. Although the pathologic hallmark of OA is loss of articular cartilage, since the cartilage has no nerve supply, the pain in OA arises only after secondary involvement of other structures, e.g., subchondral bone, synovium, or muscle (1). Thus, by the time the patient with OA presents to the physician, articular cartilage breakdown is often far advanced. No practical, reproducible, noninvasive method exists at present for the detection of early articular cartilage loss in OA. Imaging techniques, such as magnetic resonance imaging (2) and ultrasonography (3), have not proved to be sensitive or to produce
Arthritis and Rheumatism, Vol. 34, No. 4 (April 1991)
377
FIFE ET AL
378
sufficiently reproducible results for detection of “pre-
clinical” OA. Similarly, efforts to develop a serologic “marker” of OA for this purpose have not yet been successful (4-6). Therefore, radiography, although insensitive in detecting early OA and in monitoring disease progression, remains a mainstay in diagnosis and management of OA (7,8). It has been shown that an anteroposterior knee radiograph taken while the subject is standing more accurately reflects joint space narrowing (JSN) than does a knee radiograph obtained with the subject supine (9-1 1). Notably, the radiographic grading scale most widely employed today, the KellgredLawrence scale (8,12), wa s developed prior to the demonstration that a standing knee radiograph is more sensitive for assessment of JSN than a radiograph taken when the patient is supine. Furthermore, the KellgredLawrence radiographic criteria permit the diagnosis of definite OA in the presence of osteophytosis alone, without JSN. However, loss of articular cartilage, not osteophytosis, is the predominant pathologic feature of OA. Indeed, in the absence of JSN or bony changes, osteophytosis may be due to aging, and not to OA (13-15). We undertook the present study t o examine the specificity of JSN, as demonstrated in the standing knee radiograph, for articular cartilage changes of OA. The results in this series of patients, which consisted predominantly of patients with radiographic evidence of relatively “early” or “mild” OA, indicate that “false-positive” radiographic evidence of articular cartilage loss, i.e., JSN in the absence of articular cartilage damage, was common.
PATIENTS AND METHODS Patient selection. The study subjects consisted of 161 consecutive patients undergoing arthroscopy at a sports medicine practice, for evaluation of chronic knee pain. A small number of these patients were included in a previous study of a serologic marker for OA (4). Patients with known inflammatory arthritis, e.g., rheumatoid arthritis or gout, were excluded from analysis, and patients were included in the study only if a standing anteroposterior knee radiograph had been obtained shortly before arthroscopy. All radiographs were performed in the same facility by the same staff of 2 technicians, using consistent standardized techniques (cassette posterior to the knee; beam aimed at the midpoint of the patella; distance from tube to film 40”). Standing radiographs were obtained with the patient standing on both feet, with hidher knees in as full extension as possible for the individual. Lateral knee radiographs were obtained with the patient in a supine position.
Arthroscopic grading of OA. At the time of arthroscopy, the severity of the defects visible on each of 6 articular surfaces (medial and lateral femoral condyles, medial and lateral tibial plateaus, patellar surface, and trochlear groove) was graded as follows (16): grade 0 = no defect; grade 1 = superficial erosion(s); grade 2 = partial-thickness erosion(s) 2.5 cm2; and grade 4 = full-thickness erosion(s). The status of the menisci also was evaluated. Radiographic analyses. Lateral and standing anteroposterior radiographs of the knees were evaluated and graded by an experienced skeletal radiologist (EMB). A judgment concerning the degree of JSN as seen in the anteroposterior radiograph was made by comparing medial and lateral compartments of the same knee, and the right and left knee of each patient. If both compartments or both knees were abnormal, a knee radiograph from a normal subject of the same sex was used for comparison. The effects of beam position and of knee flexion on the width of the joint spaces were examined using knee radiographs of a normal volunteer. The medial and lateral joint spaces were measured using a perpendicular line drawn between the most distal aspect of the cortex of the condyle and the cortex of the adjacent tibial plateau. The radiographic severity of OA was graded according to the scale of Kellgren and Lawrence (8,12), where grade 0 = normal; grade I = doubtful narrowing of joint space and possible osteophytic lipping; grade I1 = definite osteophytes and possible narrowing of joint space; grade 111 = moderate multiple osteophytes, definite narrowing of joint space, some sclerosis, and possible deformity of bone contour; and grade IV = large osteophytes, marked narrowing of joint space, severe sclerosis, and definite deformity of bone contour. Statistical analysis. Sensitivity, specificity, and predictive value of the standing knee radiograph for the detection of OA were calculated, using the arthroscopic findings as the “gold standard.” Medial, lateral, and patellofemoral compartments were examined separately. Data for medial and lateral compartment JSN were further stratified based on the presence or absence of meniscal abnormalities. Sensitivity was calculated as the proportion of patients with cartilage changes of OA (based on arthroscopy) who were classified as having JSN by radiography. Specificity was calculated as the proportion of patients with no arthroscopic evidence of articular cartilage damage who were classified as having no JSN by radiography. The positive predictive value is the probability that those who were classified as having JSN by the radiographic criteria actually had OA by arthroscopy. The negative predictive value is the probability that those classified as normal (i.e., no JSN) by the radiographic criteria had normal articular cartilage at arthroscopy.
RESULTS One hundred thirty-four of the 161 patients studied were male, reflecting the fact that the subjects were derived from a sports medicine practice. The
379
RELATIONSHIP OF JSN TO SEVERITY OF KNEE OA
mean k SD age of the entire group was 36.4 ? 12.9 years, with a range of 12-69 years. In 13 patients, meniscectomy had previously been performed in the involved knee (8 medial, 4 lateral, 1 both menisci). Radiographs of 83 of the 161 patients (52%) were scored as grade 0 or I according to the Kellgrenl Lawrence criteria for OA severity, while 55 (34%) were scored as grade 11; only 14% of the patients had radiographically severe OA (grade III or IV). Tibiofemoral JSN. Radiographs of 76 patients showed >25% JSN in either or both tibiofemoral compartments. Twenty-five (33%) of these patients had grossly normal articular cartilage in both tibiofemoral compartments at arthroscopy (radiographic “false-positive’’ findings). Medial compartment. Of the 113 patients with no medial compartment articular cartilage degeneration at arthroscopy (grade 0), 44 (39%) had >25% medial JSN by radiography (“false-positive”) (Table 1). Nine of these patients (8%) had >50% JSN. Conversely, of the 38 patients with grade 2 4 medial compartment AC changes at arthroscopy, 11 (29%) did not have medial JSN by radiography and were considered to be radiographically “false-negative.’’ Based on the above results, the sensitivity of medial JSN for the diagnosis of grade 2-4 medial compartment articular cartilage changes at arthroscopy was 0.71. For the diagnosis of medial compartment articular cartilage degeneration of any degree (i.e., grade 1-4), the sensitivity of medial JSN was 0.67. The specificity of medial JSN for the presence of medial compartment articular cartilage degeneration was 0.61, i.e., 61% of the patients with normal (grade 0) medial compartment cartilage did not have medial JSN radiographically. The positive predictive value of medial JSN for Table 1. Relationship of medial joint space narrowing to medial Compartment cartilage degeneration at arthroscopy
Arthroscopic grade of cartilage degeneration*
Severity of radiographic joint space narrowing* None t 69
5 25 88 18
25-50%
>50%
3% 4t 0 12 3
* See Patients and Methods for explanation of grading scales. ‘t Joint space narrowing SO%
10 t 0 1 2 3
3t 0 0 I 2
* See Patients and Methods for explanation of grading scales. t Joint space narrowing 25% medial JSN had significant medial compartment articular cartilage changes at arthroscopy. When any medial compartment articular cartilage changes (grade 1-4) were present at arthroscopy, the positive predictive value of medial JSN was 0.42. Eighty-five patients were judged not to have medial JSN by radiography; of these, 69 (81%) had normal medial compartment articular cartilage at arthroscopy, while another 5 exhibited only grade 1 changes. Hence, the negative predictive value, i.e., the likelihood that a patient with no medial JSN would have essentially normal medial compartment articular cartilage (i.e., grade 0 or l), was 0.87. Lateral compartment. Thirteen of the 128 patients (10%) with normal lateral compartment articular cartilage at arthroscopy (grade 0) had >25% lateral JSN; 3 of these patients had >50% JSN. Conversely, 15 of the 24 patients (63%) with advanced arthroscopic changes in the lateral compartment, i.e., grades 2 4 , did not have lateral JSN (Table 2). Thus, the sensitivity of lateral JSN for grade 1-4 OA was 0.27, and for grade 2-4 OA it was only 0.38-much poorer than that for medial JSN; its specificity was 0.90-much higher than that for medial JSN. The positive predictive value of lateral JSN for grades 2-4 OA was 0.41 and the negative predictive value was 0.89, similar to the findings for medial JSN. Patellofemoral compartment. In 17 patients, arthroscopic evidence of articular cartilage degeneration was confined to the patella or the trochlear groove. Of these, 7 exhibited >25% medial compartment JSN, while 5 had >25% JSN in both compartments.
FIFE ET AL
380 Table 3. Medial compartment arthroscopic findings and radiographic joint space narrowing in patients with a tear or degeneration of the medial meniscus
Severity of medial compartment joint space narrowing*
Arthroscopic grade of OA in medial compartment*
Nonet
25-50%
>50%
0 1 2 3 4
32 2 1 6 0
17 2 0 8 2
3 1 0 3 2
* See Patients and Methods for explanation of grading scales. OA osteoarthritis. i Joint space narrowing 25% medial JSN (Table 3). This subgroup accounted for 26% of all patients in the series with >25% medial JSN. Of the 128 patients who had normal lateral compartment articular cartilage at arthroscopy (grade 0), gross lateral meniscal abnormalities were observed arthroscopically in 24 (19%). Four (17%) exhibited >25% lateral JSN (Table 4). These individuals represented 18% of all patients with >25% lateral JSN in this series. JSN with normal tibiofemoral articular cartilage. Thirty-six (47%) of the 76 patients in the series who had >25% JSN had normal tibiofemoral compartment cartilage at arthroscopy. JSN was associated with articular cartilage degeneration in the patellofemoral compartment in 8 of these patients, with meniscal degeneration in 18, and with both in 8. Effects of knee flexion and beam position. Radiographs of a normal knee revealed a progressive loss in the width of the medial compartment joint space with
flexion. Thus, with 0" of flexion, the joint space measured 6.0 mm; with lo" of flexion, it was 4.5 mm, a decrease of 25%. The lateral compartment joint space, which was 7.0 mm when the knee was in the neutral position, was only 5.0 mm when the knee was flexed to lo", a decrease of 29%. Similarly, when the x-ray beam was directed 1 cm below the midpoint of the patella, the width of the medial joint space of the normal knee was 17% less than when the beam was centered at the midpoint of the patella. When the beam was aimed 0.5 cm above the midpoint of the patella, the width of the medial joint space was -8% less than when it was centered.
DISCUSSION The majority of the patients in the present study had early OA based on radiographic criteria, and, since they were derived from a sports medicine clinic, the patient population was somewhat younger than most reported series of OA patients. The importance of the present study is that it permitted comparison of radiographic JSN with the anatomic changes in articular cartilage seen at arthroscopy, Our results indicate that the correlation between articular cartilage loss and tibiofemoral JSN is poor. In all but 2 of the 36 patients with >25% JSN who had no evidence of tibiofemoral articular cartilage degeneration, JSN was associated with degeneration of the patellofemoral compartment, of a meniscus, or both. The KellgredLawrence criteria, which are widely used for grading the severity of knee OA, were derived from analyses of knee radiographs obtained with the patients in a supine position, and with these criteria, the diagnosis of definite OA can be made when osteophytes are the only radiographic abnormalTable 4. Lateral compartment arthroscopic findings and radiographic joint space narrowing in patients with a tear or degeneration of the lateral meniscus
Arthroscopic grade of OA in lateral compartment*
Severity of lateral compartment joint space narrowing* Nonet
25-50%
>50%
20 0 2 4 0
3 0 1
1 0 0 1 2
1 0
* See Patients and Methods for explanation of grading scales. OA osteoarthritis. t Joint space narrowing
