Case Report Lateral Meniscal Injury After a Successful Medial Unicompartmental Knee Arthroplasty Marlon M. Mencia, FRCS (Tr & Orth), and Mark J. Ashworth, FRCS(Orth) Abstract: A case of an active 52-year-old woman who, after a medial unicompartmental knee arthroplasty, began complaining of lateral joint line pain and a persistent knee effusion. A lateral meniscal tear was diagnosed clinically, and she underwent an arthroscopic partial meniscectomy that resolved her problems. This case demonstrates the importance of considering a meniscal problem as the cause of any unexplained joint line pain in the unoperated compartment after a successful unicompartmental knee arthroplasty and not simply attributing it to progression of degenerative change within the lateral compartment. Keywords: unicompartmental knee arthroplasty, meniscal tear. © 2010 Elsevier Inc. All rights reserved. The Oxford unicompartmental knee arthroplasty (UKA) has been shown in survival analysis studies to equal the best results obtained with total knee arthroplasty [1,2]. Functionally, it performs more like a native knee joint, and hence, it has been implanted in younger patients with more active lifestyles than the traditional patient undergoing total knee arthroplasty [3]. The case presented here demonstrates that quite like a native knee, the uninvolved lateral compartment can sustain meniscal injuries. Case Report A 52-year-old shopkeeper with significant anteromedial osteoarthritis underwent a right UKA with the Oxford prosthesis (Biomet Ltd, Bridgend, United Kingdom). The Oxford phase III prosthesis was inserted using a standard medial parapatellar approach. At surgery, there were areas of exposed bone in the medial compartment, the lateral compartment was not well visualized, and the anterior cruciate ligament was functionally intact. The recovery period was uneventful with the patient being discharged home at 3 days. At the 2-week clinic visit, the patient was noted to walking comfortably and was pleased with the proce- dure. However, at the 6-week review, a new problem of lateral joint line tenderness was noted together with an effusion and reduced range of movement. The patient gave a history of a twisting injury to her right knee while getting out of a car 1 week before her clinic visit. There was no clinical evidence of infection, and radiographs were satisfactory (Fig. 1). Based on the clinical diagnosis of a lateral meniscal tear, day case arthroscopy was performed 3 weeks later. A parrot beak tear of the anterior horn of the lateral meniscus was resected, and some minor fibrillation of the articular cartilage was found (Fig. 2). From the Torbay Hospital, Torquay, Devon, UK. Submitted January 22, 2008; accepted November 26, 2008. No benefits or funds were received in support of the study. Reprint requests: Marlon M. Mencia, FRCS, The Fracture and Orthopedic Clinic 29 a St Clair Ave, St Clair Trinidad , West Indies. © 2010 Elsevier Inc. All rights reserved. 0883-5403/09/2502-0030$36.00/0 doi:10.1016/j.arth.2008.11.107 Fig. 1. Postoperative radiograph of Oxford unicompartmental knee. 333.e7 The Journal of Arthroplasty Vol. 25 No. 2 2010