The plicae are synovial septa remaining in adult life that existed in early fetal life. The suprapatellar plica separates the suprapatellar pouch from the knee joint. The plica syndrome has clinical significance, which has been occasionally overlooked, but the pathophysiology of symptomatic plicae may be hard to explain. To evaluate the clinical significance of the suprapatellar plicae, the authors reviewed 34 cases in 23 patients with vague pain around the knee and a total septum of the suprapatellar plica at arthroscopic examination from September 1991 to December 1993. The follow-up period was from 6 months to 2 years and 9 months. The most common presenting symptom was chronic mild knee pain, aggravated by prolonged squatting or standing, with other patients reporting recurrent swelling, instability, giving-way, or a feeling of snapping. The objective findings include palpable band on the superomedial side, audible snapping, and local tenderness, but there were no significant abnormal findings in the laboratory. The radiographic findings were few, with sclerosis of the articular surface of the patella in 2(6%), malalignment in 1(3%), and mild degenerative change in 4 cases(12%). Five of 11 patients evaluated by bone scan had increased uptake around the patellofemoral joint, and 7 of 13 knees had a relatively small suprapatellar bursa on conventional arthrogram or pneumoarthrogram. At arthroscopy, a suprapatellar plicae with complete septum was identified in 30 of 34 cases (88%) and associated lesions presented as meniscal tears, loose body, and discoid meniscus without tear. The complete plicae were surgically excised under arthroscopic control in 30 patients and the results were excellent in 22 patients (73%), good in 5 (17%), and poor in 3 (10%)at 17 months follow-up; there were no failures. In our opinion, the complete suprapatellar plica is clinically significant in patients who have equivocal diagnosis of knee problems and further studies of the pathophysiology of complete suprapatellar plica are needed.