Review Question - QID 219805

According to the Kellgren-Lawrence classification, grade 3 osteoarthritis features moderate multiple osteophytes, definite narrowing of the joint space, some sclerosis, and possible deformity of bone ends, which is best depicted in Figure 5.

The Kellgren-Lawrence (KL) classification is the most commonly used system for radiographic interpretation of osteoarthritis (OA) in the knee. Kellgren and Lawrence originally studied radiographic findings of osteoarthritis in coal miners in 1952 and noted the common radiographic findings associated with osteoarthritis. The two authors later developed their five-grade classification system to delineate the severity of OA on radiographic images. The grading system is as follows:

Grade 0: No radiographic signs of OA.
Grade 1: Doubtful narrowing of joint space and possible ostephytic lipping.
Grade 2: Definite osteophytes and possible narrowing of joint space.
Grade 3: Moderate multiple osteophytes, definite narrowing of joint space, some sclerosis, and possible deformity of bone ends.
Grade 4: Large osteophytes, marked narrowing of joint space, severe sclerosis, and definite deformity of bone ends.

Classically, Kellgren and Lawrence described grades 2 or less as none or possible OA and grades more than 2 as definite or mild OA. This classification system helps clinicians assess the severity and progression of OA, report data for epidemiologic studies, and guide treatment decisions.

In 1957, Kellgren and Lawrence published a study to determine the inter- and intra-observer correlation coefficients of their newly minted osteoarthritis classification system. Two observers evaluated 510 radiographs of eight joints (distal interphalangeal joint, metacarpophalangeal joint, carpometacarpal joint, the wrist, cervical spine, lumbar spine, hip, and knee) in 85 randomly selected patients ages 55 to 64 years old. To evaluate reliability, the authors used the previously discussed five-grade system to classify osteoarthritis by two observers on four different occasions. The knee had the highest intraobserver correlation coefficient (r = 0.83) and highest interobserver correlation coefficient (r = 0.83) of the 8 joints studied. The authors concluded that the grading system was reproducible and reliable, particularly when assessing the knee joint.

Kohn et al. reviewed the Kellgren-Lawrence osteoarthritis classification system. The review highlights the history and significance of the KL system, including epidemiological studies, guiding clinicians, and frequently a medical record requirement for insurance authorization. Similarly to the 1957 article above, other authors have found similar reproducibility of the classification system for grading OA. The authors suggest that, based on previous studies, using the Rosenberg radiograph (45-degree posteroanterior flexion weight-bearing radiograph) may provide higher interrater reliability than the AP radiograph used in the original article. The limitations of the KL system include a disregard for the patellofemoral joint and an assumption of linear radiographic progression of OA (osteophyte formation before joint space narrowing, etc). The authors conclude by recognizing the importance of the KL system in clinical practice and research due to its high diagnostic accuracy and universal use.

Figures/Illustrations:
Figure A is an AP radiograph of a right knee showing grade 4 OA with large osteophytes, marked joint space narrowing, severe sclerosis, and definite deformity of bone ends with a varus deformation.
Figure B is the AP of a right knee showing grade 1 OA with doubtful narrowing of the joint space and possible osteophytic lipping on the lateral tibial condyle.
Figure C is the AP of a right knee showing grade 4 OA with large osteophyte formation, marked joint space narrowing, severe sclerosis, and deformation of bone ends.
Figure D is the AP of a right knee showing grade 2 OA due to the presence of definite osteophytes (lateral femoral condyle) and possible narrowing of joint space without any deformity of bone ends.
Figure E is the AP of a right knee showing grade 3 OA with multiple osteophytes, definite narrowing of joint space, and sclerosis.
Illustration A is a table with descriptions and example radiographs of the Kellgren-Lawrence classification of osteoarthritis.

Incorrect Answers:
Answer choice 1: The radiograph in Figure A features large osteophytes, marked joint space narrowing, severe sclerosis, and definite deformity of bone ends, demonstrating a grade 4 osteoarthritic knee.
Answer choice 2: The radiograph in Figure B shows grade 1 OA with doubtful narrowing of the joint space and possible osteophytic lipping on the lateral tibial condyle.
Answer choice 3: The radiograph in Figure C shows large osteophyte formation, marked joint space narrowing, severe sclerosis, and deformation of bone ends consistent with grade 4 osteoarthritis.
Answer choice 4: The radiograph in Figure D demonstrates grade 2 OA due to the presence of osteophytes on the lateral femoral condyle and possible narrowing of joint space without any deformity of bone ends.