BRIEF REPORT Infrapatellar Plica as a Cause of Anterior Knee Pain Christine R. Boyd, MD,* Colin Eakin, MD,† and Gordon O. Matheson, MD, PhD* Objective: This study seeks to show that in the case of a patient not responding to nonoperative measures for the treatment of anterior knee pain, arthroscopic release of a symptomatic infrapatellar plica can successfully resolve the disability. Design: We report a retrospective study of 12 cases of anterior knee pain not responding to nonoperative treatment that underwent iso- lated infrapatellar plica resection without other noted knee pathology. Setting: Patients were evaluated and treated in an outpatient ortho- pedic sports medicine clinic. Participants: Any patient who presented with anterior knee pain, underwent subsequent arthroscopy, and was treated by isolated resec- tion of the infrapatellar plica was included in the study. Intervention: The surgical procedure involved arthroscopic division of the infrapatellar plica at its attachment on the superior inter- condylar notch of the femur. Main Outcome Measurements: Patients were reviewed at least 12 months following the date of surgery. Two subjective knee scales were used to assess knee function. Results: A subjective scale used in prior studies assessing symp- tomatic medial plica demonstrated 91% percent (11 of 12) excellent (6) or good (5) outcomes at follow-up greater than 1 year. The Knee Injury and Osteoarthritis Outcome Scores of knee function on the subscales of pain, symptoms, activities of daily living, sports activity, and quality of life were 97, 96, 99, 99, and 87, respectively. Conclusions: These cases demonstrate a potential role for the infrapatellar plica as a cause of anterior knee pain. A prospective study is warranted to measure causality. Key Words: anterior knee pain, infrapatellar plica (Clin J Sport Med 2005;15:98–103) A nterior knee pain is one of the most common musculo- skeletal complaints in sports medicine. It is especially prevalent in the adolescent and young athlete. The causes of anterior knee pain are numerous, 1 yet there are still a significant number of cases without obvious etiology, termed idiopathic anterior knee pain. 2 Many of these patients remain symptom- atic despite appropriate conservative management. 3,4 Pre- viously, idiopathic anterior knee pain has been attributed to retropatellar cartilage changes. However, it is now known that the symptoms of idiopathic anterior knee pain do not correlate well with cartilage changes. 3 A prospective, randomized, controlled, blindly assessed study from England involving 45 knees in adolescents with anterior knee pain despite 3 months of conservative treatment assigned the only 4 knees with isolated infrapatellar plica to the group that underwent diagnostic arthroscopy without resection of the plica. Of these 4 patients, 3 continued to have pain 6 months after surgery. One of these knees underwent repeat arthroscopy with resection of the infrapatellar plica and complete resolution of pain postoperatively. 5 Despite this study showing some indication that the infrapatellar plica may be a source of anterior knee pain, most recent literature on the pathology of plica claims that the infrapatellar plica has little clinical relevance and does not cause symptoms. 6–8 To date, there has been very little recorded in the litera- ture about knee pathology related to the infrapatellar plica. The question yet to be answered is whether the presence of a fibrotic or inflamed infrapatellar plica can cause symptoms that are encompassed in the diagnostic category of anterior knee pain. If so, this would explain some of the undiagnosed cases. By understanding further the cause of pain, appropriate treatment strategies could be formulated to minimize the long- term disability of chronic anterior knee pain. We have some experience with patients with anterior knee pain who have had resection of the infrapatellar plica with good subjective results. Thus, it was the aim of this study to review those cases comprehensively and obtain follow-up data from the patients to determine if a qualitative relationship existed between treatment and outcome. Such a relationship would form the basis for a more detailed, prospective study. MATERIALS AND METHODS We reviewed all surgical procedures with a CPT code of 29875 (release of plica or simple debridement) performed for anterior knee pain at our surgery center by a single orthopedic surgeon between January 1997 and July 2002. Any patient who presented with anterior knee pain, underwent subsequent arthroscopy, and was treated by isolated resection of the infrapatellar plica was included in the study. In patients with an insidious onset of symptoms, indication for surgery was sig- nificant lifestyle impairment despite at least 4 months on non- operative treatment (quadriceps muscle strengthening, bracing, taping, activity modification, and nonsteroidal anti-inflammatory Received for publication May 2004; accepted November 2004. From the *Stanford University Medical Center, Department of Orthopedic Surgery, Division of Sports Medicine, Stanford, CA; and the †Palo Alto Medical Foundation, Department of Sports Medicine, Palo Alto, CA. Reprints: Christine R. Boyd, MD, Division of Sports Medicine, Department of Orthopedic Surgery, Burnham Pavilion, Stanford University, Stanford, CA 94305-6175 (e-mail: doccb@hotmail.com). Copyright Ó 2005 by Lippincott Williams & Wilkins 98 Clin J Sport Med  Volume 15, Number 2, March 2005