At the beginning of the operation, an arthroscopic examination was performed within 1 month of the radiographic examination by an orthopaedic surgeon (WCL); that surgeon was aware of the radiographic findings for all patients at the time of the arthroscopic examination. Arthroscopic findings were recorded on compact disc (CD), and cartilage damage also was described on the operation record. We graded the severity of damage to the articular cartilage of the ankle using the Outerbridge system  modified by Curl et al. : Grade 0, no cartilage damage; Grade 1, softening of the articular cartilage; Grade 2, superficial fibrillation or fissures of the cartilage; Grade 3, deep fissuring of the cartilage without exposed bone; Grade 4, exposed bone. We defined cartilage lesions involving greater than half the AP length of the talus and greater than 5 mm in mediolateral width as cartilage damage. The highest grade of cartilage damage was used to represent the severity of OA when there were various levels of severity of cartilage damage. We correlated grading of a modified Outerbridge classification with that of radiographic classifications. We categorized cartilage damage into ‘nonarthritic’ and ‘arthritic’ to determine the sensitivity, specificity, and predictive values of radiographic parameters. Outerbridge Grades 0 and 1 were categorized as ‘nonarthritic’. Outerbridge Grades 2, 3, and 4 were categorized as ‘arthritic’.
After a discussion of 10 radiographs showing different grades, the three observers graded all radiographs using the modified Kellgren-Lawrence, Takakura et al., and van Dijk et al. grading systems. To determine interobserver reliability, each observer reviewed 40 randomly selected radiographs twice with no questions or discussion between observers allowed during grading. To assess intraobserver reliability, the same radiographs were placed in a new order and were classified under the same conditions by each observer 1 month later. We determined agreement of the three observers using Cohen's kappa statistical analysis . As kappa can vary from 0 (complete disagreement) to 1 (complete agreement), we also used the weighted kappa  to take into account partial agreement; consequently, the weighted kappa is greater than kappa when calculated for the same cases.
Spearman's rank order correlation coefficient was used to determine the correlation between the radiographic grades of OA (modified Kellgren-Lawrence, Takakura et al., and van Dijk et al.) and the severity of articular cartilage damage. Differences between the correlation coefficients and squared correlation coefficients of the three radiographic classifications were tested using Steiger's Z-test . A bar chart was constructed to obtain the distribution of cartilage damage based on each radiographic grading. The chi square test was used to evaluate the differences in the status of articular cartilage damage according to talar tilting in the ankles with medial joint space narrowing. Using arthroscopy as the diagnostic standard reference (gold standard), we calculated the sensitivity, specificity, predictive value, and odds ratios (with 95% confidence intervals [CIs]) of the radiographic parameters for detecting arthritic change of the ankle. We compared values for sensitivity and specificity among the radiographic parameters using McNemar's test. The level of significance was set at p < 0.05.
For the interobserver comparisons, weighted kappa ranged from 0.58 to 0.89, and for intraobserver comparisons, weighted kappa ranged from 0.51 to 0.85 (Table 2).
The correlation coefficients between radiographic classifications and arthroscopic findings were similar for the modified Kellgren-Lawrence, Takakura et al., and van Dijk et al. grading systems (0.53, 0.42, and 0.42, respectively) (Table 3). Of 98 ankles, 70 (71%) with medial joint space narrowing, according to the Takakura et al. and van Dijk et al. grading systems, had a wide range of severity of cartilage damage (Fig. 2). Patients with medial joint space narrowing with talar tilting showed a higher (p < 0.001) rating for arthritic change compared with medial joint space narrowing without talar tilting (Table 4).
The sensitivity of spurs and medial joint space narrowing was greater than that of the other radiographic parameters (p < 0.001 and p < 0.001, respectively). The specificity of medial joint space narrowing combined with talar tilting was greater than that of the other parameters (p < 0.001, p < 0.001, and p < 0.001, respectively). Medial joint space narrowing with talar tilting showed the highest positive predictive value (98%) for arthritic change and the highest odds ratio (71.6) (Table 5).
Several radiographic grading systems have been used to evaluate OA of the ankle and select between treatment options [28, 40, 48, 52]. However, to be useful in clinical practice and scientific studies, such systems must be reliable and predict the fate of the cartilage and the prognosis of the patient. We therefore questioned (1) whether radiographic grading of OA of the ankle is reproducible, (2) whether the grading system reflects cartilage changes observed during arthroscopy, and (3) whether the spur, joint space narrowing, and talar tilting predict cartilage damage in medial ankle OA.
The major limitation of our study is that it did not explore the correlation between cartilage damage and pain or joint function of the patients. The literature suggests radiographic grading and arthroscopically verified cartilage damage do not predict pain or joint function [15, 20, 26, 33]. However, along with alignment, severity of cartilage damage is considered by some authors [9, 40, 50] as an important factor in determining whether to perform surgery in patients with mid-stage ankle OA. Realignment surgery has been performed for mid-stage ankle OA after confirmation of partial cartilage damage during the operation [40, 48]. Alignment is assessed easily on plain radiographs, however, the cartilage condition is difficult to assess particularly in mid-stage OA. Our data suggest we can improve predictability of cartilage damage before we examine the ankles arthroscopically. Second, our study is based on a small number of ankles. However, ankle OA occurs approximately eight to 10 times less than knee OA [14, 25, 42], and it was difficult to collect many cases of medial ankle OA. Third, we had only one observer judge the severity of cartilage damage by arthroscopy. We could not evaluate interobserver reliability in this study because we did not open the joint in most cases although high interobserver reliability has been described in grading cartilage damage of the knee [3, 8]. Therefore, it is reasonable for a well-trained observer to arthroscopically judge the severity of cartilage damage. Fourth, we did not subclassify the area of cartilage damage in the areas of the medial gutter and talar dome. This subclassification was omitted because we were unable to determine whether an ankle with denudation of the articular cartilage in the gutter and normal cartilage in the talar dome or an ankle with normal cartilage in the gutter and a partial-thickness defect of the cartilage in the talar dome was more advanced. We found many intermediate cases involving a spectrum ranging from cartilage damage confined to the medial surface of the talus to cartilage damage only on the dome of the talus. Therefore, we did not subdivide the area of cartilage damage according to site. Finally, we did not include lateral OA in this study. Lateral OA frequently is seen in late-stage adult-acquired flatfoot. However, the incidence of lateral OA is very low in the population in our country, and we performed arthroscopic examinations in only four such ankles during the same period. We suspect inclusion of lateral OA would be a confounding factor when analyzing features of medial OA. We know of no report of degenerative changes confined to the joint between the lateral malleolus and talus, and every case of lateral OA also has a tendency toward talar tilting. We therefore presume the severity of cartilage change would be similar to that in medial OA with medial joint space narrowing with talar tilting.
If a grading system is not reliable, correlations between the grades and the severity of OA determined by some independent method would not be meaningful. Therefore, we first performed observer reliability testing for each grading system. The description of each grade in this article was taken from those of Kijowski et al. , and we used the radiographs of the other joints shown in the original article by Kellgren and Lawrence  for reference because that article had no radiographs of ankles. Others [11, 21, 27] have used similar descriptions. We believe the terminology used in the Kellgren-Lawrence grading system is somewhat subjective, perhaps the explanation for lower intraobserver and interobserver reliability. For this reason, we recommend the system of Kijowski et al.  because we believe it has a clearer definition of each grade.
As a result of the focus on osteophytes and the assumption that OA would result in joint space narrowing with the Kellgren-Lawrence grading system, other grading systems have been developed [18, 19, 32, 44, 47]. The intraobserver and interobserver reliability of these systems reportedly ranges from 0.18 to 0.95 [18, 19, 32, 44]. We found that the modified Kellgren-Lawrence, Takakura et al., and van Dijk et al. grading systems had reliability ranging from 0.51 to 0.89.
We presumed tilting of the talus in the ankle mortise would result in asymmetric overloading in the small area of cartilage; therefore, we examined the predictability of cartilage change based on medial joint space narrowing with or without talar tilting. Although several studies have reported talar tilting [22, 40, 50], none has clearly shown its clinical importance. Our data suggest the sensitivity and specificity of radiographs to predict arthroscopic damage improved when talar tilting was considered. The relatively low predictive power of medial joint space narrowing without talar tilting may be attributable to pseudo-narrowing of the medial joint space as a result of a deviated ankle mortise or spur changes on the medial malleolus or talus. However, joint space narrowing without talar tilting does not always indicate pseudo-narrowing. In our study, 12 (39%) of 31 ankles with joint space narrowing without talar tilting had cartilage damage, and most of them had narrowing greater than half of the medial gutter. We believe including talar tilting when radiographically assessing patients will enhance our ability to predict cartilage damage in medial ankle OA.
1. Altman, R. Classification of disease: osteoarthritis. Semin Arthritis Rheum
1991; 20: 40-47. 10.1016/0049-0172(91)90026-V
2. Ayral, X., Dougados, M., Listrat, V., Bonvarlet, JP., Simonnet, J. and Amor, B. Arthroscopic evaluation of chondropathy in osteoarthritis of the knee. J Rheumatol.
1996; 23: 698-706.
3. Ayral, X., Gueguen, A., Ike, RW., Bonvarlet, JP., Frizziero, L., Kalunian, K., Moreland, LW., Myers, S., O'Rourke, KS., Roos, H., Altman, R. and Dougados, M. Inter-observer reliability of the arthroscopic quantification of chondropathy of the knee. Osteoarthritis Cartilage.
1998; 6: 160-166. 10.1053/joca.1998.0108
4. Blackburn, WD Jr. Bernreuter, WK., Rominger, M. and Loose, LL. Arthroscopic evaluation of knee articular cartilage: a comparison with plain radiographs and magnetic resonance imaging. J Rheumatol.
1994; 21: 675-679.
5. Boegard, T., Rudling, O., Petersson, IF., Sanfridsson, J., Saxne, T., Svensson, B. and Jonsson, K. Postero-anterior radiogram of the knee in weight-bearing and semiflexion: comparison with MR imaging. Acta Radiol.
1997; 38: 1063-1070.
6. Brandt, KD., Fife, RS., Braunstein, EM. and Katz, B. Radiographic grading of the severity of knee osteoarthritis: relation of the Kellgren and Lawrence grade to a grade based on joint space narrowing, and correlation with arthroscopic evidence of articular cartilage degeneration. Arthritis Rheum.
1991; 34: 1381-1386. 10.1002/art.1780341106
7. Buckwalter, JA., Saltzman, C. and Brown, T. The impact of osteoarthritis: implications for research. Clin Orthop Relat Res
2004; 427: (suppl):S6-S15. 10.1097/01.blo.0000143938.30681.9d
8. Cameron, ML., Briggs, KK. and Steadman, JR. Reproducibility and reliability of the outerbridge classification for grading chondral lesions of the knee arthroscopically. Am J Sports Med.
2003; 31: 83-86.
9. Cheng, YM., Huang, PJ., Hung, SH., Chen, TB. and Lin, SY. The surgical treatment for degenerative disease of the ankle. Int Orthop.
2000; 24: 36-39. 10.1007/s002640050009
10. Cohen, J. A coefficient of agreement for nominal scales. Educ Psychol Measure.
1960; 20: 37-47. 10.1177/001316446002000104
11. Cooper, C., Egger, P., Coggon, D., Hart, DJ., Masud, T., Cicuttini, F., Doyle, DV. and Spector, TD. Generalized osteoarthritis in women: pattern of joint involvement and approaches to definition for epidemiological studies. J Rheumatol.
1996; 23: 1938-1942.
12. Coull, R., Raffiq, T., James, LE. and Stephens, MM. Open treatment of anterior impingement of the ankle. J Bone Joint Surg Br.
2003; 85: 550-553. 10.1302/0301-620X.85B4.13871
13. Curl, WW., Krome, J., Gordon, ES., Rushing, J., Smith, BP. and Poehling, GG. Cartilage injuries: a review of 31,516 knee arthroscopies. Arthroscopy.
1997; 13: 456-460. 10.1016/S0749-8063(97)90124-9
14. Cushnaghan, J. and Dieppe, P. Study of 500 patients with limb joint osteoarthritis: I. Analysis by age, sex, distribution of symptomatic joint sites. Ann Rheum Dis.
1991; 50: 8-13. 10.1136/ard.50.1.8
15. Dieppe, PA., Cushnaghan, J. and Shepstone, L. The Bristol ‘OA500’ study: progression of osteoarthritis (OA) over 3 years and the relationship between clinical and radiographic changes at the knee joint. Osteoarthritis Cartilage.
1997; 5: 87-97. 10.1016/S1063-4584(97)80002-7
16. Fife, RS., Brandt, KD., Braunstein, EM., Katz, BP., Shelbourne, KD., Kalasinski, LA. and Ryan, S. Relationship between arthroscopic evidence of cartilage damage and radiographic evidence of joint space narrowing in early osteoarthritis of the knee. Arthritis Rheum.
1991; 34: 377-382. 10.1002/art.1780340402
17. Fleiss JL. Statistical Methods for Rates and Proportions.
Ed 2. New York, NY: Wiley; 1981:38-46.
18. Galli, M., Santis, V. and Tafuro, L. Reliability of the Ahlback classification of knee osteoarthritis. Osteoarthritis Cartilage.
2003; 11: 580-584. 10.1016/S1063-4584(03)00095-5
19. Gunther, KP. and Sun, Y. Reliability of radiographic assessment in hip and knee osteoarthritis. Osteoarthritis Cartilage.
1999; 7: 239-246. 10.1053/joca.1998.0152
20. Hannan, MT., Felson, DT. and Pincus, T. Analysis of the discordance between radiographic changes and knee pain in osteoarthritis of the knee. J Rheumatol.
2000; 27: 1513-1517.
21. Hart, DJ., Spector, TD., Brown, P., Wilson, P., Doyle, DV. and Silman, AJ. Clinical signs of early osteoarthritis: reproducibility and relation to x ray changes in 541 women in the general population. Ann Rheum Dis.
1991; 50: 467-470. 10.1136/ard.50.7.467
22. Hayashi, K., Tanaka, Y., Kumai, T., Sugimoto, K. and Takakura, Y. Correlation of compensatory alignment of the subtalar joint to the progression of primary osteoarthritis of the ankle. Foot Ankle Int.
2008; 29: 400-406. 10.3113/FAI.2008.0400
23. Hepple, S., Winson, IG. and Glew, D. Osteochondral lesions of the talus: a revised classification. Foot Ankle Int.
1999; 20: 789-793.
24. Hernborg, J. and Nilsson, BE. The relationship between osteophytes in the knee joint, osteoarthritis and aging. Acta Orthop Scand.
1973; 44: 69-74. 10.3109/17453677308988675
25. Huch, K., Kuettner, KE. and Dieppe, P. Osteoarthritis in ankle and knee joints. Semin Arthritis Rheum.
1997; 26: 667-674. 10.1016/S0049-0172(97)80002-9
26. Hunter, DJ., McDougall, JJ. and Keefe, FJ. The symptoms of osteoarthritis and the genesis of pain. Rheum Dis Clin North Am.
2008; 34: 623-643. 10.1016/j.rdc.2008.05.004
27. Jordan, JM., Luta, G., Stabler, T., Renner, JB., Dragomir, AD., Vilim, V., Hochberg, MC., Helmick, CG. and Kraus, VB. Ethnic and sex differences in serum levels of cartilage oligomeric matrix protein: the Johnston County Osteoarthritis Project. Arthritis Rheum.
2003; 48: 675-681. 10.1002/art.10822
28. Kellgren, JH. and Lawrence, JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis.
1957; 16: 494-502. 10.1136/ard.16.4.494
29. Kijowski, R., Blankenbaker, D., Stanton, P., Fine, J. and Smet, A. Arthroscopic validation of radiographic grading scales of osteoarthritis of the tibiofemoral joint. AJR Am J Roentgenol.
2006; 187: 794-799. 10.2214/AJR.05.1123
30. Kijowski, R., Blankenbaker, D., Stanton, P., Fine, J. and Smet, A. Correlation between radiographic findings of osteoarthritis and arthroscopic findings of articular cartilage degeneration within the patellofemoral joint. Skeletal Radiol.
2006; 35: 895-902. 10.1007/s00256-006-0111-7
31. Kijowski, R., Blankenbaker, DG., Stanton, PT., Fine, JP. and Smet, AA. Radiographic findings of osteoarthritis versus arthroscopic findings of articular cartilage degeneration in the tibiofemoral joint. Radiology.
2006; 239: 818-824. 10.1148/radiol.2393050584
32. Lane, NE., Nevitt, MC., Genant, HK. and Hochberg, MC. Reliability of new indices of radiographic osteoarthritis of the hand and hip and lumbar disc degeneration. J Rheumatol.
1993; 20: 1911-1918.
33. Lawrence, JS., Bremner, JM. and Bier, F. Osteo-arthrosis: prevalence in the population and relationship between symptoms and x-ray changes. Ann Rheum Dis.
1966; 25: 1-24.
34. Lysholm, J., Hamberg, P. and Gillquist, J. The correlation between osteoarthrosis as seen on radiographs and on arthroscopy. Arthroscopy.
1987; 3: 161-165. 10.1016/S0749-8063(87)80058-0
35. Masciocchi, C., Catalucci, A. and Barile, A. Ankle impingement syndromes. Eur J Radiol
1998; 27: (suppl 1):S70-S73. 10.1016/S0720-048X(98)00045-X
36. Niek van Dijk C. Anterior and posterior ankle impingement. Foot Ankle Clin.
37. Nihal, A., Rose, DJ. and Trepman, E. Arthroscopic treatment of anterior ankle impingement syndrome in dancers. Foot Ankle Int.
2005; 26: 908-912.
38. Ogilvie-Harris, DJ., Mahomed, N. and Demaziere, A. Anterior impingement of the ankle treated by arthroscopic removal of bony spurs. J Bone Joint Surg Br.
1993; 75: 437-440.
39. Outerbridge, RE. The etiology of chondromalacia patellae. J Bone Joint Surg Br.
1961; 43: 752-757.
40. Pagenstert, GI., Hintermann, B., Barg, A., Leumann, A. and Valderrabano, V. Realignment surgery as alternative treatment of varus and valgus ankle osteoarthritis. Clin Orthop Relat Res.
2007; 462: 156-168. 10.1097/BLO.0b013e318124a462
41. Rosenberg, TD., Paulos, LE., Parker, RD., Coward, DB. and Scott, SM. The forty-five-degree posteroanterior flexion weight-bearing radiograph of the knee. J Bone Joint Surg Am.
1988; 70: 1479-1483.
42. Saltzman, CL., Salamon, ML., Blanchard, GM., Huff, T., Hayes, A., Buckwalter, JA. and Amendola, A. Epidemiology of ankle arthritis: report of a consecutive series of 639 patients from a tertiary orthopaedic center. Iowa Orthop J.
2005; 25: 44-46.
43. Schäfer, D., Boss, A. and Hintermann, B. Accuracy of arthroscopic assessment of anterior ankle cartilage lesions. Foot Ankle Int.
2003; 24: 317-320.
44. Scott, WW Jr. Lethbridge-Cejku, M., Reichle, R., Wigley, FM., Tobin, JD. and Hochberg, MC. Reliability of grading scales for individual radiographic features of osteoarthritis of the knee: the Baltimore longitudinal study of aging atlas of knee osteoarthritis. Invest Radiol.
1993; 28: 497-501. 10.1097/00004424-199306000-00005
45. Scranton, PE Jr. McDermott, JE. and Rojers, JV. The relationship between chronic ankle instability and variations in mortise anatomy and impingement spurs. Foot Ankle Int.
2000; 21: 657-664.
46. Steiger, JH. Tests for comparing elements of a correlation matrix. Psychol Bull.
1980; 87: 245-251. 10.1037/0033-2909.87.2.245
47. Sun, Y., Gunther, KP. and Brenner, H. Reliability of radiographic grading of osteoarthritis of the hip and knee. Scand J Rheumatol.
1997; 26: 155-165. 10.3109/03009749709065675
48. Takakura, Y., Tanaka, Y., Kumai, T. and Tamai, S. Low tibial osteotomy for osteoarthritis of the ankle: results of a new operation in 18 patients. J Bone Joint Surg Br.
1995; 77: 50-54.
49. Takao, M., Uchio, Y., Naito, K., Kono, T., Oae, K. and Ochi, M. Arthroscopic treatment for anterior impingement exostosis of the ankle: application of three-dimensional computed tomography. Foot Ankle Int.
2004; 25: 59-62.
50. Tanaka, Y., Takakura, Y., Hayashi, K., Taniguchi, A., Kumai, T. and Sugimoto, K. Low tibial osteotomy for varus-type osteoarthritis of the ankle. J Bone Joint Surg Br.
2006; 88: 909-913. 10.2106/JBJS.E.00472
51. Tol, JL., Verhagen, RA., Krips, R., Maas, M., Wessel, R., Dijkgraaf, MG. and Dijk, CN. The anterior ankle impingement syndrome: diagnostic value of oblique radiographs. Foot Ankle Int.
2004; 25: 63-68.
52. Dijk, CN., Verhagen, RA. and Tol, JL. Arthroscopy for problems after ankle fracture. J Bone Joint Surg Br.
1997; 79: 280-284. 10.1302/0301-620X.79B2.7153
53. Verhagen, RA., Mass, M., Dijkgraaf, MG., Tol, JL., Krips, R. and Dijk, CN. Prospective study on diagnostic strategies in osteochondral lesions of the talus: is MRI superior to helical CT? J Bone Joint Surg Br.
2005; 87: 41-46. 10.2106/JBJS.D.02871
54. Wada, M., Baba, H., Imura, S., Morita, A. and Kusaka, Y. Relationship between radiographic classification and arthroscopic findings of articular cartilage lesions in osteoarthritis of the knee. Clin Exp Rheumatol.
1998; 16: 15-20.
55. Wright, RW., Boyce, RH., Michener, T., Shyr, Y., McCarty, EC. and Spindler, KP. Radiographs are not useful in detecting arthroscopically confirmed mild chondral damage. Clin Orthop Relat Res.
2006; 442: 245-251. 10.1097/01.blo.0000167670.03197.c2
56. Wu, CW., Morrell, MR., Heinze, E., Concoff, AL., Wollaston, SJ., Arnold, EL., Singh, R., Charles, C., Skovrun, ML., Fitzgerald, JD., Moreland, LW. and Kalunian, KC. Validation of American College of Rheumatology classification criteria for knee osteoarthritis using arthroscopically defined cartilage damage scores. Semin Arthritis Rheum.
2005; 35: 197-201. 10.1016/j.semarthrit.2005.06.002