Objectives-To (a) develop an atlas of line drawings for the assessment and grading of narrowing and osteophyte (that is, changes of osteoarthritis) on knee radiographs, and (b) compare the performance of this atlas with that of the standard Osteoarthritis Research Society (OARS) photographic atlas of radiographs. Methods-Normal joint space widths (grade 0) for the medial and lateral tibiofemoral and medial and lateral patellofemoral compartments were obtained from a previous community study. Grades 1-3 narrowing in each compartment was calculated separately for men and women, grade 3 being bone on bone, grades 1 and 2 being two thirds and one third the value of grade 0. Maximum osteophyte size (grade 3) for each of eight sites was determined from 715 bilateral knee x ray films obtained in a knee osteoarthritis (OA) hospital clinic; grades 1-2 were calculated as two thirds and one third reductions in the area of grade 3. Drawings for narrowing and osteophyte were presented separately. 50 sets of bilateral knee x ray radiographs (standing, extended anteroposterior; flexed skyline) showing a spectrum of OA grades were scored by three observers, twice using the OARS atlas and twice using the drawn atlas. Results-Intraobserver and interobserver reproducibility was similar and generally good with both atlases, though varied according to site. All three observers preferred the line drawing atlas for ease and convenience of use. Higher scores for patellofemoral narrowing and lower scores for osteophyte, especially medial femoral osteophyte, were seen using the line drawing atlas, showing that the two atlases are not equivalent instruments. Conclusion-A logically derived line drawing atlas for grading of narrowing and osteophyte at the knee has been produced. The atlas showed comparable reproducibility with the OARS atlas, but was discordant in several aspects of grading. Such a system has several theoretical and practical advantages and should be considered for use in knee OA studies.

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Objectives: To examine the size and direction of osteophyte in knee osteoarthritis (OA) and to determine associations between osteophyte size and other radiographic features. Methods: Knee radiographs (standing extended anteroposterior and 30 degrees flexion skyline views) were examined from 204 patients referred to hospital with symptomatic knee OA (155 women, 49 men; mean age 70, range 34-91 years). A single observer assessed films for osteophyte size and direction at eight sites; narrowing in each compartment; varus/valgus angulation; patellofemoral subluxation; attrition; and chondrocalcinosis using a standard atlas, direct measurement, or visual assessment. For analysis, one OA knee was selected at random from each subject. Results: Osteophyte direction at the eight sites was divisible into five categories. At all sites, except for the lateral tibial plateau and the medial patella, osteophyte direction varied according to (a) the size of osteophyte and (b) the degree of local narrowing. At the medial femur, medial tibia, and lateral femur osteophyte direction changed from being predominantly horizontal to predominantly vertical with increasing size. The size of osteophyte correlated positively with the severity of local narrowing, except for the medial patellofemoral compartment where osteophyte size correlated positively with the severity of narrowing in the medial tibiofemoral compartment. Logistic regression analysis showed that osteophyte size was associated not only with local narrowing but also with local malalignment and bone attrition, and that chondrocalcinosis was positively associated with osteophyte size at multiple sites. Conclusion: In patients referred to hospital with knee OA different patterns of osteophyte direction are discernible. Osteophyte size is associated with local compartmental narrowing but also local alignment and attrition. Chondrocalcinosis is associated with osteophytosis throughout the joint. These data suggest that both local biomechanical and constitutional factors influence the size and direction of osteophyte formation in knee OA.

Horizontalization of the lamina and the facets is a pathoanatomic risk factor that can predispose for the development of degenerative spondylolisthesis. If dysfunction of the disc occurs in addition to these conditions, spondylolisthesis may develop.