Magnetic Resonance Imaging of the Patellofemoral Articular Cartilage

Anterior knee pain is the leading cause of knee pain in patients younger than 45 years and can be caused by cartilage lesions in the patellofemoral compartment, which is frequently involved in cartilage disease of the knee [1]. Although the true incidence of cartilage lesions is unknown, numerous studies report chondral injuries in 60–66% of knees undergoing arthroscopy [2–4]. Cartilage injuries of the knee affect just under a million Americans annually and result in more than 200,000 surgical procedures [2]. Lesions are most commonly found on the weight-bearing femoral condyle (43–58%) with the majority of them located on the medial femoral condyle. While patellar lesions account for 11–36% of all cartilage lesions, trochlear lesions are less frequently encountered, accounting for approximately 6–16% of all lesions [3–5]. In 90% of cases, the defect size is reported to be less than 4 cm2 in the knee. Athletic activities are frequently associated with the diagnosis of chondral lesions [3, 6]. Patellofemoral osteoarthritis accounts for approximately 65% of patients with symptomatic knee osteoarthritis (OA) [7]. Even small changes in the patellofemoral articular cartilage surfaces have a profound activity-limiting effect on normal function. A recent meta-analysis revealed that in up to 52% of patients with knee pain or symptomatic osteoarthritis, MRI revealed cartilage lesions in the patellofemoral joint [8]. Despite its high prevalence, patellofemoral cartilage lesions remain underdiagnosed clinically and on multimodality imaging studies [9].