Kellgren–Lawrence scoring system underestimates cartilage damage when indicating TKA: preoperative radiograph versus intraoperative photograph

Introduction

The Kellgren–Lawrence score helps the orthopedic surgeon to classify the severity of knee osteoarthritis (OA) before total knee arthroplasty (TKA). There might be a discrepancy between subjective complaints of the patients and radiologically visible changes of the knee joint in many cases. In this context, we performed a prospective clinical study to compare the preoperative degree of knee OA using the Kellgren–Lawrence score with the intraoperative extent of cartilage damage during primary TKA.

Materials and methods

A total of 251 primary TKA surgeries due to a primary knee OA were prospectively included. Preoperative Kellgren–Lawrence score was determined using standardized preoperative plain radiographs of three views; anteroposterior, lateral and skyline of the patella by a senior radiologist. Intraoperatively, in all cases, photographs of the medial, lateral, and patellofemoral joint compartments were taken. Using the International Cartilage Repair Society (ICRS) score, the degree of chondromalacia was assessed. Subsequently, correlation analysis was performed using the Pearson–Clopper 95% confidence interval (CI).

Results

There were higher intraoperative scores compared to the preoperative scores in 160 of all cases (63.7% of 251, 95% CI 57.5–69.7%). A mismatch of two score grade points was found in 8.4% (95% CI 5.3–12.5%). The most common mismatch was noted in patients with preoperative Kellgren–Lawrence score of 3 and an intraoperative score of 4 in 48.2% (95% CI 41.9–54.6%).

Conclusions

The preoperative radiographs using Kellgren–Lawrence underestimate the severity of knee osteoarthritis. The true extent of articular cartilage damage can be better appreciated intraoperatively. In patients undergoing primary TKA, the correlation of clinical symptoms with radiological findings is crucial in deciding when to perform the surgery. Besides, other imaging modalities may be used as an adjunct when the clinical findings and plain radiographs do not correlate.