Knee arthrography was performed in 22 patients suffering from persistent articular symptoms after meniscectomy. In 3 cases a surgically proved tear of the opposite meniscus was assessed. In 4 cases no meniscal tear was found, but 3 out of these patients had a significant anatomic lesion. In 15 cases meniscectomy was found to be incomplete, and a residual posterior horn of the medial meniscus was observed, normal in shape in 7 cases, torn or detached in 8. It is suggested that the persistence of the posterior horn of the medial meniscus after meniscectomy may cause the persistent symptoms; the value of knee arthrography before surgery is emphasized.