The radiographic classification of medial gonarthrosis. Correlation with operation methods in 200 knees.

Ahlbäck's classification of gonarthrosis can be applied with improved precision by careful interpretation of anteroposterior varus stress and lateral radiographs of the knee. The tibial lesion in early gonarthrosis is located in the anterior and middle part of the medial plateau. In more advanced disease, when the anterior cruciate ligament is invariably damaged, the lesion extends to the posterior margin of the medial tibial plateau. We studied the preoperative radiographs of 200 knees with arthrosis. We were able to predict the integrity of the anterior cruciate ligament (and the use of unicompartmental arthroplasty) with 95 percent accuracy and rupture or damage to the anterior cruciate ligament (and the use of total condylar arthroplasty) with 100 percent accuracy. We believe that the Ahlbäck classification reflects the anatomic and pathologic progression of medial compartment gonarthrosis, and is of value in allowing more accurate comparisons to be made of different methods of treatment.