Diagnostic Radiology
Compartmental Evaluation of Osteoarthritis of the Knee A Comparative Study of Available Diagnostic Modalities 1
Roger H. Thomas, M.D., Donald Resnick, M.D., Naomi P. Alazrakl, M.D., Dale Daniel, M.D., and Richard Greenfield, M.D. The distribution and severity of osteoarthritis were investigated in 56 knees by history and physical examination, assessment of knee function, radiography with and without weightbearing, double-contrast arthrography, and 99mTc-polyphosphate bone imaging. Compartmental involvement (medial, lateral, patellofemoral) was graded independently by 2 or 3 observers for each modality and was correlated with that observed during arthroscopy or direct surgical inspection. The more involved compartments were graded abnormal by all methods. In the less involved compartments, the gamma camera image was most sensitive to pathology, followed by arthrography. The choice of surgical technique and the prognosis depend upon accurate preoperative knowledge of the extent of disease. INDEX TERMS: Joints, radionuclide studies. Knee, arthritis. Knee, radiography. Knee, radionuclide studies
Radiology 118: 585-594, September 1975
HE STANDARD
evaluation of osteoarthritis of the
compartment disease in the qualitative analysis by all modalities but were not included in the quantitative evaluation.
Tknee includes clinical and roentgenographic exami-
nation. Routine radiographic changes such as jointspace narrowing, sclerosis, osteophytosis, and subchondral cyst formation reflect relatively late pathological alterations; although radiography during weightbearing may be of additional aid, other modalities are necessary for earlier diagnosis. Sensitive, reproducible methods of evaluation are of particular importance in unicompartmental surgery, in which the choice of technique and the prognosis depend upon accurate preoperative knowledge of the distribution and extent of disease. We wish to describe and compare various diagnostic modalities, including clinical examination, radiography with and without weight-bearing, arthrography, and bone imaging in the evaluation of osteoarthritis involving the medial, lateral, and patellofemoral compartments of the knee and to correlate the findings with those from arthroscopy and direct surgical inspection.
Clinical Examination and Assessment of Knee Function
All patients were examined by an orthopedic surgeon (D.O. or R.G.). Each compartment was evaluated as 0 (normal), +1 (mild disease), +2 (moderate disease), or +3 (severe disease) on the basis of localization of pain, warmth, tenderness, and crepitation. Knee function was evaluated by a physical therapist using the system described by Convery and Beber (8). A normal knee was assigned 100 points (absence of pain 40, normal function 50, normal range of motion 5, no deformity 5).
=
=
=
=
Radiography With and Without Weight-Bearing
MATERIAL AND METHODS
A total of 56 osteoarthritic knees in 52 men and 1 woman being considered for surgery in the Knee Clinic at the Veterans Administration Hospital in San Diego from January 1973 to April 1974 were evaluated by (a) history and physical examination, (b) assessment of knee function, (c) radiography with and without weightbearing, (d) double-contrast arthrography, and (e) 99mTc-polyphosphate bone imaging. Patients with known rheumatoid arthritis, gout, previous sepsis, or fracture or osteotomy of the proximal tibia or distal femur were excluded. The age range was 38 to 81 years (mean, 60 years). Patients who had undergone patellectomy were considered to have patellofemoral
Routine radiographs included anteroposterior and lateral projections; in many instances a "tunnel" view was obtained. Tangential films of the patella and stress radiographs were occasionally employed. During weightbearing, roentgenograms were obtained at a distance of 1.8 m (6 ft.) with the patient standing on one leg while balancing himself with his other hand. In arriving at a value for each compartment, 2 of the 3 observers (D.R., R.T., and D.O.) assigned a grade of to +3 to each of four recognized routine radiographic parameters of osteoarthritis-joint-space narrowing, sclerosis, osteophytosis, and subchondral cyst formation-and obtained the average value. The degree of joint-space loss was estimated as (no evidence of joint-space loss) to +3 (complete obliteration of the articular space), using the criteria of Ahlback (1). Sub-
°
°
1 From the Departments of Radiology (R. H. T., D. R.), Nuclear Medicine (N. P. A.), and Orthopedic Surgery (D. D., R. G.), Veterans Administration Hospital, and University Hospital, University of California at San Diego, San Diego, Calif. Presented at the Sixtieth Scientific Assembly and Annual Meeting of the Radiological Society of North America, Chicago, 111., Dec. 1-6, 1974. sjh
585
586
ROGER
H. THOMAS AND OTHERS
ROUTINE RADIOGRAPH 56 KNEES
o NORMAL
56KNEES 4 NORMAL
MEDIAL
LATERAL
~ 4 0 1
2S ': 0
MEDIAL
LATERAL
PATE LLOFEMORAL
PATELLOFEMORAL
ARTHROGRAM
BONE SCAN
56 KNeES 1 NORMAL
56KNEES
3 NORMAL
( ] )
16
MEDIAL
LATERAL
36
1
MEDIAL
LATERAL
PATELLOFEMORAL
Fig. 1. Site of compartmental involvement as determined by various diagnostic modalities. The number of knees demonstrating abnormality in each compartment is represented. The overlapping portions of the circles indicate the number of knees in which more than one compartment was judged abnormal. Table I: Extent of Disease as Determined by Various Diagnostic Modalities* Routine Radiographt
Arthrogramt
Radionuclidet Image
25
7 14
2 16
6 9
23
7
9
Clinical Examinationt Normal Unicompartmental disease Medial Lateral Patellofemoral Bicompartmental disease Medial Lateral Patellofemoral Tricompartmental disease
0
2 61
0
11 0
7 47
5 39
42
55
47 2 45 32
37 7 34 43
42 18 24 42
0
13
54 14
0 0
* The numbers represent the frequency of abnormality (expressed as a percentage) based on the number of examinations. t Ineludes evaluation of 56 knees. t Includes evaluation of 33 knees in which all three compartments were assessed.
September 1975
exposures of each meniscus were obtained in various degrees of rotation. Overhead films were then taken; these included a tangential exposure of the patella, a cross-table projection with the patient supine and in a mild Trendelenburg position, and a lateral projection with the knee flexed. Evaluation of the menisci, the femoral and tibial cartilage in the medial and lateral compartments, and the patellar cartilage in the patellofemoral space was undertaken by 2 of the 3 observers (D.R, RT., and D.O.). The menisci were graded as 0 (normal contour without evidence of swelling or tear), + 1 (localized meniscal swelling or small tear), +2 (moderate-sized tear or degeneration), or +3 (extensive tear or disintegration). The articular cartilage was evaluated and a figure obtained for each compartment (medial and lateral) averaging the femoral and tibial alterations. The cartilage on the posterior surface of the patella was studied to grade the patellofemoral compartment. Cartilaginous abnormalities were listed as 0 (smooth cartilaginous surfaces with no apparent thinning), + 1 (minimal thinning and irregularity), +2 (large localized defects or moderate thinning and irregularity), or +3 (severe denudation of cartilage).
Bone Imaging
Following thorough hydration, each patient was given an intravenous injection of 15 mCi of 9 9 mTc-polyphosphate. Two hours later, images of each knee were obtained in the anterior and lateral projections, using an Anger scintillation camera with a high-resolution/lowenergy collimator. A total of 200,000 counts were collected for each image, using a 25 % window centered on the 140-keV photopeak of technetium. Three observers (N.A., RT., and D.O.) graded the films independently as 0 (normal), + 1 (limited increased uptake), +2 (moderate, localized increased uptake), or +3 (moderate to marked increased uptake).
Arthroscopy and Surgical Observations
chondral cysts were evaluated as 0 (absent), + 1 (1 to 2 small cysts), +2 (single large or multiple small cysts), or +3 (many large cysts). Osteophytes were graded 0 to +3 depending upon their number and size. Sclerosis was judged as 0 (absent), + 1 (mild or localized eburnation), +2 (moderate increase in density), or +3 (severe, widespread sclerosis). Radiographs obtained during weight-bearing were evaluated for loss of joint space (graded 0 to +3), varus or valgus angulation, and subluxation.
The orthopedic staff directly inspected 21 knees by arthroscopy in 11 and arthrotomy in 10; (18 knees were examined by one of us (D.O.). A total of 46 compartments were adequately evaluated and graded 0 (normal) to +3 (severe) on the basis of cartilage fibrillation and erosion. RESULTS
Clinical Evaluation Arthrography
Double-contrast arthrography of the knee was performed with a horizontal beam (2, 11). Seven to 8 ml of 76 % Renografin (methylglucamine diatrizoate, Squibb) and 15-20 ml of room air were administered and 8-12
The mean functional assessment of all 56 knees was 65 points using the Convery system. On the basis of the history and physical examination, no knees were rated normal, 25 % had unicompartmental disease, 61 % had bicompartmental disease, and 14% had tricompart-
Vol.
116
COMPARTMENTAL EVALUATION OF OSTEOARTHRITIS OF THE KNEE
mental disease (TABLE I). The medial compartment was involved in 52/56 knees (Fig. 1). Radiography With and Without Weight-Bearing
Routine radiographs were normal in 4/56 knees (7 %). Bicompartmental abnormality was more common than uni- or tricompartmental involvement (TABLE I). The medial compartment was most frequently altered and was commonly associated with patellofemoral disease (Fig. 1). Osteophytosis was the most prevalent radiographic abnormality; its presence in the patellofemoral and lateral compartments with little other local alteration accounted for a high incidence of bi- and tricompartmental involvement in this series. Osteophyte formation appeared as marginal bony outgrowths or intra-articular surface irregularities with sharpening of the tibial spines. Although small osteophytes were not uncommon in compartments with an intact joint space, larger outgrowths were found more frequently in areas of narrowing. Joint-space narrowing was most consistent in the medial and patellofemoral compartments; although on occasion only one was narrowed, it was more common to find narrowing in both joint spaces. Symmetrical loss of joint space in the medial and lateral or medial, lateral, and patellofemoral spaces was unusual in this series. Although patellofemoral joint-space narrowing was readily apparent on lateral radiographs, axial projections were helpful for confirmation of the findings and localization of joint-space loss to the lateral or medial facets. Associated bony changes in the narrowed patellofemoral compartments consisted of flattening and eburnation along the posterior surface of the patella, "scooping out" of the distal anterior femur, and osteophytosis. Sclerosis in the subchondral bone was most frequent in the tibia or in both the tibia and femur. Sclerotic bone was consistently found in compartments with articular narrowing and was most severe in areas of extreme joint-space loss. Although sclerosis was localized to the immediate subchondral bone in most cases, it sometimes extended 3-5 cm from the joint margin. Subchondral cysts were not common, though they were occasionally seen in the medial compartment in combination with joint-space loss and eburnation. Vacuum phenomena within the joint were noted in several knees and were usually confined to the medial compartment; they were more evident in compartments with moderate narrowing and were difficult to identify in patients with severe joint-space loss. Meniscal calcification was relatively uncommon and usually confined to the medial compartment. Large effusions made it difficult to evaluate loss of the patellofemoral joint space in many cases. Radiographs of 42 knees were obtained during weight-bearing. In 27 the medial compartment demonstrated an increased loss of joint space in the upright
587
Diagnostic Radiology
position. The lateral compartment became narrowed during weight-bearing in 6 knees, did not change in 28, and increased in width in 8. Thus although collapse of the more involved compartment during weight-bearing was not unusual, significant collapse of the less-involved side was uncommon; the latter frequently became wider as the contralateral compartment collapsed. Stress films were available for several patients but did not contribute additional information. Using weight-bearing films, alignment of the knee was evaluated on the basis of the angle formed by the intersection of lines drawn through the longitudinal axes of the femur and tibia. Nine knees exhibited valgus of 0_5 0 , and 1 showed valgus of 20 0 . Varus measuring 1_5 0 was seen in 12,6-10 0 in 13, and 11-15 0 in 7. Ten knees exhibited 2-4 mm of subluxation, while 2 knees showed 6-10 mm. Arthrography
All 56 knees were studied by arthrography. One knee was judged to be normal. Disease was unicompartmental in 9 knees (16 %), bicompartmental in 22 (39 %), and tricompartmental in 24 (43 %) (TABLE I; Fig. 1). The medial compartment was most frequently involved. The cartilaginous changes in the medial femoral-tibial space were commonly severe, with grade 3 abnormalities in 26 knees and grade 2 in 12. The lateral compartment demonstrated severe changes in 2 knees and moderate abnormalities in 9. In 45/56 knees, alterations in the lateral space were either absent or mild. The patellofemoral space was quantitatively evaluated in 50 instances; in 6, previous patellectomy or technical inadequacies prevented such examination. Grade 3 abnormalities were present in 11 knees, grade 2 in 6. The vast majority of patients had no or mild patellofemoral disease. Meniscectomy had been performed prior to arthrography in 6 knees, being done medially in 5 and laterally in 1. The medial meniscus was abnormal in 39/51 knees in which it had not been removed; it was graded as + 1 in 8, +2 in 20, and +3 in 11. Of these 39 knees, 38 had associated medial compartment abnormalities. Of the 12 knees in which the medial meniscus was normal, 8 had abnormal medial compartments. Three of the 5 patients with previous medial meniscectomy had irregular meniscal remnants. The lateral meniscus was abnormal in 14/55 knees; in 12 of them, the lateral compartment was also abnormal. Fifteen of the 41 knees with a normal lateral meniscus had evidence of cartilaginous alterations in the lateral compartment. Bone Imaging
Of the 56 knees examined by frontal or frontal and lateral imaging, 16 had isolated medial compartment abnormality and 36 had medial and lateral compartment
588
ROGER H. THOMAS AND OTHERS
abnormality (Fig. 1). Only one patient had increased activity confined to the lateral compartment. Two knees had normal activity in all compartments; one additional knee had normal activity in the medial and lateral compartments, but the patellofemoral space was not evaluated. The greatest concentration of radioisotope (graded +3) was usually seen in the medial compartment (28/52 abnormal medial compartments). A total of 4/37 abnormal lateral compartments and 4/22 abnormal patellofemoral compartments were graded +3. Arthroscopy and Surgical Observations
A total of 23 knees were operated on during the study. Twelve high tibial osteotomies, 7 medial meniscectomies, 3 total knee replacements, and 1 patellectomy were performed. The joint could be directly inspected at surgery when arthrotomy was performed. Total knee replacement allowed inspection of 3 compartments, while meniscectomy permitted adequate examination of the ipsilateral compartment and patellofemoral space. A total of 22 compartments in 10 knees were examined at arthrotomy. The joint capsule was not opened during high tibial osteotomy; however, 24 compartments in 11 knees were inspected using a Stortz arthroscope. At first only selected critical compartments were examined, but subsequent arthroscopy of the knee included evaluation of all three compartments. Proliferative degenerative synovitis, decreased range of motion, and decreased patellar excursion occasionally made complete arthroscopic examination difficult. A total of 16 medial compartments, 11 lateral compartments, and 19 patellofemoral compartments were inspected. Thirteen medial, 7 lateral, and 15 patellofemoral compartments demonstrated cartilage fibrillation or erosion (Figs. 5 and 6). DISCUSSION
Osteoarthritis does not involve the three compartments of the knee symmetrically. When disease is limited to one of the two weight-bearing compartments (medial or lateral), surgery may be required; this may include unicompartmental prosthetic replacement (14) or high tibial osteotomy (3, 9). As these and other reconstructive procedures depend upon the status of the opposite compartment, it is important to know the extent of the disease in each compartment before beginning the procedure. This study was undertaken to compare diagnostic modalities in the quantitative evaluation of the severity of degenerative arthritis, recognizing that all such techniques are qualitative. To attain maximum precision in evaluation, grading systems were developed prior to beginning the study. Two examiners evaluating a test independently sometimes differed by one level in their quantitative assessment but never by two.
September 1975
Standard Evaluation of Osteoarthritis of the Knee
The routine evaluation of degenerative disease of the knee includes clinical and radiographic examination. Pain and stiffness are gradual in onset. Physical signs include warmth, joint-line tenderness, effusion and/or synovial thickening, crepitation, restricted motion, ligamentous instability, malalignment, and alterations of gait. The clinical symptoms and signs may correlate poorly with roentgenographic alterations such as jointspace narrowing, sclerosis, osteophytosis, and subchondral cyst formation, which are easily distinguished from the changes seen in other types of arthritis. The presence of marginal osteophytes by itself may not justify the diagnosis of osteoarthritis (12); loss of joint space, subchondral eburnation, and cyst formation are more important criteria of significant cartilage and bony abnormality. The routine radiographic examination should include roentgenograms taken during weightbearing (13). Joint-space collapse in the more involved medial or lateral compartment, representing loss of articular cartilage, can be assessed more accurately on upright films. A total of 52/56 knees had evidence of medial compartment disease on clinical examination, while 48 had similar evidence on routine radiographs. The lateral compartment was judged clinically abnormal in 15 knees and radiographically abnormal in 19 (Fig. 1). Both diagnostic modes appeared to be relatively insensitive to involvement of the less diseased compartments when compared with other techniques.
Standard Evaluation plus Arthrography
Although the addition of arthrography to the standard evaluation of osteoarthritis has distinct advantages, certain technical limitations must be understood: (a) Proper positioning during arthrography in the elderly osteoarthritic patient can be extremely difficult and time-consuming (16), whether horizontal-beam (11) or fluoroscopic methods (6) are employed. Aspiration of joint fluid is mandatory to ensure high-quality arthrograms and may require the assistance of two technicians. (b) Since only the portion of the cartilaginous surface tangent to the incident beam is studied adequately, multiple projections are necessary. In the fully exterlded or slightly flexed knee, serial radiographs may allow visualization of a large portion of the tiblalplateau but only a small amount of the femoral condylar surface. Roentgenograms obtained in various attitudes of knee flexion or tomography provide additional information. (c) Evaluation of the patellar cartilage is difficult. Cross-table supine radiographs and lateral projections allow visualization of the tangential portion of the cartilage on the posterior surface of the patella. Axial radiographs are helpful but technically difficult. Arthrography is inadequate in evaluation of patellar cartilage abner-
Vol. 116
malities (17), though we have employed cross-table radiography with beam angulation and tomography with some success. Despite these shortcomings, arthrography allows visualization of localized cartilaginous defects (19) or generalized cartilage thinning (6). The distribution and appearance of cartilage diminution are variable. Symmetrical, smooth thinning may reflect the changes of senescence (12). With symptomatic joint pathology, the alterations may become more extensive; a rough, irregular, pitted cartilaginous surface on arthrography probably reflects degeneration and fibrillation of the articular surface histologically. In the severely diseased compartment in which radiographs with and without weight-bearing reveal extensive loss of joint space, arthrography offers no additional information. In our study, the medial compartment was almost uniformly the one involved most extensively; the severity of disease in this compartment as diagnosed by radiography and arthrography in 42 knees was almost identical (Fig. 2). In the lateral compartment, which is not as severely affected, arthrography may allow more accurate estimation of cartilage integrity (Fig. 2). The menisci can be evaluated well by arthrography. In severe osteoarthritis and complete obliteration of the joint space, identification of complete loss of articular cartilage and dissolution of the meniscus during contrast examination is not unexpected. In the less abnormal compartments, the arthrogram may outline degenerated and torn menisci. These appear as swollen structures with irregular surfaces, horizontal collections of contrast material, or fragmented and frayed inner contours. Imbibition of the meniscal surface by contrast material may be seen. The surgeon may elect to remove the abnormal meniscus rather than perform a more extensive procedure. Arthrography in the osteoarthritic patient also allows identification of translucent loose bodies (for which single-contrast arthrography and tomography are necessary) and popliteal cysts (which require high-volume injection and vigorous exercise). Arthrography is not a noninvasive examination. Although aspiration of the joint contents may diminish the time and extent of postprocedural discomfort.' pain and swelling are not infrequent and may last 1 to 5 days. Transient synovitis following arthrography appears more commonly in patients with significant initial synovial inflammation. Standard Evaluation plus Bone Imaging
Gamma camera imaging has become established as a very sensitive diagnostic tool for early detection of bone abnormalities (7); however, the reactive bone formation detected may occur with many benign and malignant processes (5). Although investigators have noted that joint abnormality may give false-positive results on studies of metastatic skeletal disease, few have used
LATERAL COMPARTMENT (42 KNEES)
MEDIAL COMPARTMENT (42 KNEES)
3
19
4
1
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/
/
/
/
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/
/
/
4
/ /
/
3
cc
C)
1
3
/
/
/
i
2
ex:
Compartmental Evaluation of Osteoarthritis of the Knee A Comparative Study of Available Diagnostic Modalities 1
Roger H. Thomas, M.D., Donald Resnick, M.D., Naomi P. Alazrakl, M.D., Dale Daniel, M.D., and Richard Greenfield, M.D. The distribution and severity of osteoarthritis were investigated in 56 knees by history and physical examination, assessment of knee function, radiography with and without weightbearing, double-contrast arthrography, and 99mTc-polyphosphate bone imaging. Compartmental involvement (medial, lateral, patellofemoral) was graded independently by 2 or 3 observers for each modality and was correlated with that observed during arthroscopy or direct surgical inspection. The more involved compartments were graded abnormal by all methods. In the less involved compartments, the gamma camera image was most sensitive to pathology, followed by arthrography. The choice of surgical technique and the prognosis depend upon accurate preoperative knowledge of the extent of disease. INDEX TERMS: Joints, radionuclide studies. Knee, arthritis. Knee, radiography. Knee, radionuclide studies
Radiology 118: 585-594, September 1975
HE STANDARD
evaluation of osteoarthritis of the
compartment disease in the qualitative analysis by all modalities but were not included in the quantitative evaluation.
Tknee includes clinical and roentgenographic exami-
nation. Routine radiographic changes such as jointspace narrowing, sclerosis, osteophytosis, and subchondral cyst formation reflect relatively late pathological alterations; although radiography during weightbearing may be of additional aid, other modalities are necessary for earlier diagnosis. Sensitive, reproducible methods of evaluation are of particular importance in unicompartmental surgery, in which the choice of technique and the prognosis depend upon accurate preoperative knowledge of the distribution and extent of disease. We wish to describe and compare various diagnostic modalities, including clinical examination, radiography with and without weight-bearing, arthrography, and bone imaging in the evaluation of osteoarthritis involving the medial, lateral, and patellofemoral compartments of the knee and to correlate the findings with those from arthroscopy and direct surgical inspection.
Clinical Examination and Assessment of Knee Function
All patients were examined by an orthopedic surgeon (D.O. or R.G.). Each compartment was evaluated as 0 (normal), +1 (mild disease), +2 (moderate disease), or +3 (severe disease) on the basis of localization of pain, warmth, tenderness, and crepitation. Knee function was evaluated by a physical therapist using the system described by Convery and Beber (8). A normal knee was assigned 100 points (absence of pain 40, normal function 50, normal range of motion 5, no deformity 5).
=
=
=
=
Radiography With and Without Weight-Bearing
MATERIAL AND METHODS
A total of 56 osteoarthritic knees in 52 men and 1 woman being considered for surgery in the Knee Clinic at the Veterans Administration Hospital in San Diego from January 1973 to April 1974 were evaluated by (a) history and physical examination, (b) assessment of knee function, (c) radiography with and without weightbearing, (d) double-contrast arthrography, and (e) 99mTc-polyphosphate bone imaging. Patients with known rheumatoid arthritis, gout, previous sepsis, or fracture or osteotomy of the proximal tibia or distal femur were excluded. The age range was 38 to 81 years (mean, 60 years). Patients who had undergone patellectomy were considered to have patellofemoral
Routine radiographs included anteroposterior and lateral projections; in many instances a "tunnel" view was obtained. Tangential films of the patella and stress radiographs were occasionally employed. During weightbearing, roentgenograms were obtained at a distance of 1.8 m (6 ft.) with the patient standing on one leg while balancing himself with his other hand. In arriving at a value for each compartment, 2 of the 3 observers (D.R., R.T., and D.O.) assigned a grade of to +3 to each of four recognized routine radiographic parameters of osteoarthritis-joint-space narrowing, sclerosis, osteophytosis, and subchondral cyst formation-and obtained the average value. The degree of joint-space loss was estimated as (no evidence of joint-space loss) to +3 (complete obliteration of the articular space), using the criteria of Ahlback (1). Sub-
°
°
1 From the Departments of Radiology (R. H. T., D. R.), Nuclear Medicine (N. P. A.), and Orthopedic Surgery (D. D., R. G.), Veterans Administration Hospital, and University Hospital, University of California at San Diego, San Diego, Calif. Presented at the Sixtieth Scientific Assembly and Annual Meeting of the Radiological Society of North America, Chicago, 111., Dec. 1-6, 1974. sjh
585
586
ROGER
H. THOMAS AND OTHERS
ROUTINE RADIOGRAPH 56 KNEES
o NORMAL
56KNEES 4 NORMAL
MEDIAL
LATERAL
~ 4 0 1
2S ': 0
MEDIAL
LATERAL
PATE LLOFEMORAL
PATELLOFEMORAL
ARTHROGRAM
BONE SCAN
56 KNeES 1 NORMAL
56KNEES
3 NORMAL
( ] )
16
MEDIAL
LATERAL
36
1
MEDIAL
LATERAL
PATELLOFEMORAL
Fig. 1. Site of compartmental involvement as determined by various diagnostic modalities. The number of knees demonstrating abnormality in each compartment is represented. The overlapping portions of the circles indicate the number of knees in which more than one compartment was judged abnormal. Table I: Extent of Disease as Determined by Various Diagnostic Modalities* Routine Radiographt
Arthrogramt
Radionuclidet Image
25
7 14
2 16
6 9
23
7
9
Clinical Examinationt Normal Unicompartmental disease Medial Lateral Patellofemoral Bicompartmental disease Medial Lateral Patellofemoral Tricompartmental disease
0
2 61
0
11 0
7 47
5 39
42
55
47 2 45 32
37 7 34 43
42 18 24 42
0
13
54 14
0 0
* The numbers represent the frequency of abnormality (expressed as a percentage) based on the number of examinations. t Ineludes evaluation of 56 knees. t Includes evaluation of 33 knees in which all three compartments were assessed.
September 1975
exposures of each meniscus were obtained in various degrees of rotation. Overhead films were then taken; these included a tangential exposure of the patella, a cross-table projection with the patient supine and in a mild Trendelenburg position, and a lateral projection with the knee flexed. Evaluation of the menisci, the femoral and tibial cartilage in the medial and lateral compartments, and the patellar cartilage in the patellofemoral space was undertaken by 2 of the 3 observers (D.R, RT., and D.O.). The menisci were graded as 0 (normal contour without evidence of swelling or tear), + 1 (localized meniscal swelling or small tear), +2 (moderate-sized tear or degeneration), or +3 (extensive tear or disintegration). The articular cartilage was evaluated and a figure obtained for each compartment (medial and lateral) averaging the femoral and tibial alterations. The cartilage on the posterior surface of the patella was studied to grade the patellofemoral compartment. Cartilaginous abnormalities were listed as 0 (smooth cartilaginous surfaces with no apparent thinning), + 1 (minimal thinning and irregularity), +2 (large localized defects or moderate thinning and irregularity), or +3 (severe denudation of cartilage).
Bone Imaging
Following thorough hydration, each patient was given an intravenous injection of 15 mCi of 9 9 mTc-polyphosphate. Two hours later, images of each knee were obtained in the anterior and lateral projections, using an Anger scintillation camera with a high-resolution/lowenergy collimator. A total of 200,000 counts were collected for each image, using a 25 % window centered on the 140-keV photopeak of technetium. Three observers (N.A., RT., and D.O.) graded the films independently as 0 (normal), + 1 (limited increased uptake), +2 (moderate, localized increased uptake), or +3 (moderate to marked increased uptake).
Arthroscopy and Surgical Observations
chondral cysts were evaluated as 0 (absent), + 1 (1 to 2 small cysts), +2 (single large or multiple small cysts), or +3 (many large cysts). Osteophytes were graded 0 to +3 depending upon their number and size. Sclerosis was judged as 0 (absent), + 1 (mild or localized eburnation), +2 (moderate increase in density), or +3 (severe, widespread sclerosis). Radiographs obtained during weight-bearing were evaluated for loss of joint space (graded 0 to +3), varus or valgus angulation, and subluxation.
The orthopedic staff directly inspected 21 knees by arthroscopy in 11 and arthrotomy in 10; (18 knees were examined by one of us (D.O.). A total of 46 compartments were adequately evaluated and graded 0 (normal) to +3 (severe) on the basis of cartilage fibrillation and erosion. RESULTS
Clinical Evaluation Arthrography
Double-contrast arthrography of the knee was performed with a horizontal beam (2, 11). Seven to 8 ml of 76 % Renografin (methylglucamine diatrizoate, Squibb) and 15-20 ml of room air were administered and 8-12
The mean functional assessment of all 56 knees was 65 points using the Convery system. On the basis of the history and physical examination, no knees were rated normal, 25 % had unicompartmental disease, 61 % had bicompartmental disease, and 14% had tricompart-
Vol.
116
COMPARTMENTAL EVALUATION OF OSTEOARTHRITIS OF THE KNEE
mental disease (TABLE I). The medial compartment was involved in 52/56 knees (Fig. 1). Radiography With and Without Weight-Bearing
Routine radiographs were normal in 4/56 knees (7 %). Bicompartmental abnormality was more common than uni- or tricompartmental involvement (TABLE I). The medial compartment was most frequently altered and was commonly associated with patellofemoral disease (Fig. 1). Osteophytosis was the most prevalent radiographic abnormality; its presence in the patellofemoral and lateral compartments with little other local alteration accounted for a high incidence of bi- and tricompartmental involvement in this series. Osteophyte formation appeared as marginal bony outgrowths or intra-articular surface irregularities with sharpening of the tibial spines. Although small osteophytes were not uncommon in compartments with an intact joint space, larger outgrowths were found more frequently in areas of narrowing. Joint-space narrowing was most consistent in the medial and patellofemoral compartments; although on occasion only one was narrowed, it was more common to find narrowing in both joint spaces. Symmetrical loss of joint space in the medial and lateral or medial, lateral, and patellofemoral spaces was unusual in this series. Although patellofemoral joint-space narrowing was readily apparent on lateral radiographs, axial projections were helpful for confirmation of the findings and localization of joint-space loss to the lateral or medial facets. Associated bony changes in the narrowed patellofemoral compartments consisted of flattening and eburnation along the posterior surface of the patella, "scooping out" of the distal anterior femur, and osteophytosis. Sclerosis in the subchondral bone was most frequent in the tibia or in both the tibia and femur. Sclerotic bone was consistently found in compartments with articular narrowing and was most severe in areas of extreme joint-space loss. Although sclerosis was localized to the immediate subchondral bone in most cases, it sometimes extended 3-5 cm from the joint margin. Subchondral cysts were not common, though they were occasionally seen in the medial compartment in combination with joint-space loss and eburnation. Vacuum phenomena within the joint were noted in several knees and were usually confined to the medial compartment; they were more evident in compartments with moderate narrowing and were difficult to identify in patients with severe joint-space loss. Meniscal calcification was relatively uncommon and usually confined to the medial compartment. Large effusions made it difficult to evaluate loss of the patellofemoral joint space in many cases. Radiographs of 42 knees were obtained during weight-bearing. In 27 the medial compartment demonstrated an increased loss of joint space in the upright
587
Diagnostic Radiology
position. The lateral compartment became narrowed during weight-bearing in 6 knees, did not change in 28, and increased in width in 8. Thus although collapse of the more involved compartment during weight-bearing was not unusual, significant collapse of the less-involved side was uncommon; the latter frequently became wider as the contralateral compartment collapsed. Stress films were available for several patients but did not contribute additional information. Using weight-bearing films, alignment of the knee was evaluated on the basis of the angle formed by the intersection of lines drawn through the longitudinal axes of the femur and tibia. Nine knees exhibited valgus of 0_5 0 , and 1 showed valgus of 20 0 . Varus measuring 1_5 0 was seen in 12,6-10 0 in 13, and 11-15 0 in 7. Ten knees exhibited 2-4 mm of subluxation, while 2 knees showed 6-10 mm. Arthrography
All 56 knees were studied by arthrography. One knee was judged to be normal. Disease was unicompartmental in 9 knees (16 %), bicompartmental in 22 (39 %), and tricompartmental in 24 (43 %) (TABLE I; Fig. 1). The medial compartment was most frequently involved. The cartilaginous changes in the medial femoral-tibial space were commonly severe, with grade 3 abnormalities in 26 knees and grade 2 in 12. The lateral compartment demonstrated severe changes in 2 knees and moderate abnormalities in 9. In 45/56 knees, alterations in the lateral space were either absent or mild. The patellofemoral space was quantitatively evaluated in 50 instances; in 6, previous patellectomy or technical inadequacies prevented such examination. Grade 3 abnormalities were present in 11 knees, grade 2 in 6. The vast majority of patients had no or mild patellofemoral disease. Meniscectomy had been performed prior to arthrography in 6 knees, being done medially in 5 and laterally in 1. The medial meniscus was abnormal in 39/51 knees in which it had not been removed; it was graded as + 1 in 8, +2 in 20, and +3 in 11. Of these 39 knees, 38 had associated medial compartment abnormalities. Of the 12 knees in which the medial meniscus was normal, 8 had abnormal medial compartments. Three of the 5 patients with previous medial meniscectomy had irregular meniscal remnants. The lateral meniscus was abnormal in 14/55 knees; in 12 of them, the lateral compartment was also abnormal. Fifteen of the 41 knees with a normal lateral meniscus had evidence of cartilaginous alterations in the lateral compartment. Bone Imaging
Of the 56 knees examined by frontal or frontal and lateral imaging, 16 had isolated medial compartment abnormality and 36 had medial and lateral compartment
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abnormality (Fig. 1). Only one patient had increased activity confined to the lateral compartment. Two knees had normal activity in all compartments; one additional knee had normal activity in the medial and lateral compartments, but the patellofemoral space was not evaluated. The greatest concentration of radioisotope (graded +3) was usually seen in the medial compartment (28/52 abnormal medial compartments). A total of 4/37 abnormal lateral compartments and 4/22 abnormal patellofemoral compartments were graded +3. Arthroscopy and Surgical Observations
A total of 23 knees were operated on during the study. Twelve high tibial osteotomies, 7 medial meniscectomies, 3 total knee replacements, and 1 patellectomy were performed. The joint could be directly inspected at surgery when arthrotomy was performed. Total knee replacement allowed inspection of 3 compartments, while meniscectomy permitted adequate examination of the ipsilateral compartment and patellofemoral space. A total of 22 compartments in 10 knees were examined at arthrotomy. The joint capsule was not opened during high tibial osteotomy; however, 24 compartments in 11 knees were inspected using a Stortz arthroscope. At first only selected critical compartments were examined, but subsequent arthroscopy of the knee included evaluation of all three compartments. Proliferative degenerative synovitis, decreased range of motion, and decreased patellar excursion occasionally made complete arthroscopic examination difficult. A total of 16 medial compartments, 11 lateral compartments, and 19 patellofemoral compartments were inspected. Thirteen medial, 7 lateral, and 15 patellofemoral compartments demonstrated cartilage fibrillation or erosion (Figs. 5 and 6). DISCUSSION
Osteoarthritis does not involve the three compartments of the knee symmetrically. When disease is limited to one of the two weight-bearing compartments (medial or lateral), surgery may be required; this may include unicompartmental prosthetic replacement (14) or high tibial osteotomy (3, 9). As these and other reconstructive procedures depend upon the status of the opposite compartment, it is important to know the extent of the disease in each compartment before beginning the procedure. This study was undertaken to compare diagnostic modalities in the quantitative evaluation of the severity of degenerative arthritis, recognizing that all such techniques are qualitative. To attain maximum precision in evaluation, grading systems were developed prior to beginning the study. Two examiners evaluating a test independently sometimes differed by one level in their quantitative assessment but never by two.
September 1975
Standard Evaluation of Osteoarthritis of the Knee
The routine evaluation of degenerative disease of the knee includes clinical and radiographic examination. Pain and stiffness are gradual in onset. Physical signs include warmth, joint-line tenderness, effusion and/or synovial thickening, crepitation, restricted motion, ligamentous instability, malalignment, and alterations of gait. The clinical symptoms and signs may correlate poorly with roentgenographic alterations such as jointspace narrowing, sclerosis, osteophytosis, and subchondral cyst formation, which are easily distinguished from the changes seen in other types of arthritis. The presence of marginal osteophytes by itself may not justify the diagnosis of osteoarthritis (12); loss of joint space, subchondral eburnation, and cyst formation are more important criteria of significant cartilage and bony abnormality. The routine radiographic examination should include roentgenograms taken during weightbearing (13). Joint-space collapse in the more involved medial or lateral compartment, representing loss of articular cartilage, can be assessed more accurately on upright films. A total of 52/56 knees had evidence of medial compartment disease on clinical examination, while 48 had similar evidence on routine radiographs. The lateral compartment was judged clinically abnormal in 15 knees and radiographically abnormal in 19 (Fig. 1). Both diagnostic modes appeared to be relatively insensitive to involvement of the less diseased compartments when compared with other techniques.
Standard Evaluation plus Arthrography
Although the addition of arthrography to the standard evaluation of osteoarthritis has distinct advantages, certain technical limitations must be understood: (a) Proper positioning during arthrography in the elderly osteoarthritic patient can be extremely difficult and time-consuming (16), whether horizontal-beam (11) or fluoroscopic methods (6) are employed. Aspiration of joint fluid is mandatory to ensure high-quality arthrograms and may require the assistance of two technicians. (b) Since only the portion of the cartilaginous surface tangent to the incident beam is studied adequately, multiple projections are necessary. In the fully exterlded or slightly flexed knee, serial radiographs may allow visualization of a large portion of the tiblalplateau but only a small amount of the femoral condylar surface. Roentgenograms obtained in various attitudes of knee flexion or tomography provide additional information. (c) Evaluation of the patellar cartilage is difficult. Cross-table supine radiographs and lateral projections allow visualization of the tangential portion of the cartilage on the posterior surface of the patella. Axial radiographs are helpful but technically difficult. Arthrography is inadequate in evaluation of patellar cartilage abner-
Vol. 116
malities (17), though we have employed cross-table radiography with beam angulation and tomography with some success. Despite these shortcomings, arthrography allows visualization of localized cartilaginous defects (19) or generalized cartilage thinning (6). The distribution and appearance of cartilage diminution are variable. Symmetrical, smooth thinning may reflect the changes of senescence (12). With symptomatic joint pathology, the alterations may become more extensive; a rough, irregular, pitted cartilaginous surface on arthrography probably reflects degeneration and fibrillation of the articular surface histologically. In the severely diseased compartment in which radiographs with and without weight-bearing reveal extensive loss of joint space, arthrography offers no additional information. In our study, the medial compartment was almost uniformly the one involved most extensively; the severity of disease in this compartment as diagnosed by radiography and arthrography in 42 knees was almost identical (Fig. 2). In the lateral compartment, which is not as severely affected, arthrography may allow more accurate estimation of cartilage integrity (Fig. 2). The menisci can be evaluated well by arthrography. In severe osteoarthritis and complete obliteration of the joint space, identification of complete loss of articular cartilage and dissolution of the meniscus during contrast examination is not unexpected. In the less abnormal compartments, the arthrogram may outline degenerated and torn menisci. These appear as swollen structures with irregular surfaces, horizontal collections of contrast material, or fragmented and frayed inner contours. Imbibition of the meniscal surface by contrast material may be seen. The surgeon may elect to remove the abnormal meniscus rather than perform a more extensive procedure. Arthrography in the osteoarthritic patient also allows identification of translucent loose bodies (for which single-contrast arthrography and tomography are necessary) and popliteal cysts (which require high-volume injection and vigorous exercise). Arthrography is not a noninvasive examination. Although aspiration of the joint contents may diminish the time and extent of postprocedural discomfort.' pain and swelling are not infrequent and may last 1 to 5 days. Transient synovitis following arthrography appears more commonly in patients with significant initial synovial inflammation. Standard Evaluation plus Bone Imaging
Gamma camera imaging has become established as a very sensitive diagnostic tool for early detection of bone abnormalities (7); however, the reactive bone formation detected may occur with many benign and malignant processes (5). Although investigators have noted that joint abnormality may give false-positive results on studies of metastatic skeletal disease, few have used
LATERAL COMPARTMENT (42 KNEES)
MEDIAL COMPARTMENT (42 KNEES)
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