Arthroscopy is considered the “gold-standard” for the diagnosis of internal knee pathologies aside of being a minimal invasive surgical procedure to treat intraarticular lesions [
1]. Yet, arthroscopic intervention has potential complications, some of which could be lethal such as pulmonary embolism [
2], and therefore its use should be implemented cautiously and guided according to appropriate indications. Magnetic Resonance Imaging (MRI), although questioned almost three decades ago concerning clinical value and cost-effectiveness for knee disorders [
3], has gained popularity as the best noninvasive diagnostic modality and is currently widely used for the evaluation of intra-articular knee lesions [
4]. Along the years, this imaging modality was the focus for studies that explored its diagnostic accuracy compared to knee arthroscopy as the “gold-standard”. The anterior cruciate ligament (ACL) and the menisci were the most commonly investigated structures in this respect. Accuracy measures of MRI for these structures range from 80 to 95% in most studies [
5‐
12]. Contrary, accuracy of MRI for knee articular cartilage lesions is more controversial with several reports showing sensitivity as low as 15% and as high as 60% depending on the depth of the lesion [
13‐
15]. Only few studies were designed to identify factors associated with false negative MRI. Several researchers identified specific tear patterns of the menisci that were more likely to present false negative on MRI. The lateral meniscus showed decreased MRI sensitivity for peripheral longitudinal tears at the posterior horn [
8,
16]. Another study showed similar tear characteristics in the medial meniscus that were associated with false negative MRI (i.e. peripheral longitudinal tears at the posterior horn) when these occurred concomitantly with ACL tears [
17]. A short time interval from the injury to performing the MRI was also associated with false negative MRI for meniscal tears but only in the case of concomitant ACL tears [
17] and not when the meniscal tear was isolated without accompanying ACL damage [
8]. Awareness of the aforementioned information concerning specific factors which were found to be associated with a false negative MRI could potentially assist in improving MRI interpretation, although there were a few limitations of previously reported data on MRI accuracy that should be remembered. These include incorporating low-magnet strength MRI which is rarely used today for the diagnosis of knee lesions (i.e. lower than 1.5-Tesla) [
1], not indicating accuracy measures for specific areas in the meniscus in some studies (i.e. anterior horn, body, posterior horn) [
1,
10,
11], and using multiple MRI sequencing techniques in a single series of patients [
1]. Because MRI accuracy depends on magnet strength [
1,
10], on the specific location of the lesion, and possibly on aging changes that occur within these intraarticular structures [
18‐
20], more specific data about MRI accuracy could be useful to improve clinical judgement when viewing the MRI as an important step during management and decision making for a suspected knee lesion. In addition, with the increasing surgeons’ awareness of subtle lesions in recent years that might be challenging to identify on MRI it is possible that MRI accuracy measures would evolve over time. Such subtle lesions include small medial meniscocapsular lesions [
21], lateral meniscocapsular (i.e. popliteo-meniscal fasciculi) lesions that result in meniscus hypermobility [
22,
23] and medial meniscus ramp lesions which are challenging to identify even during arthroscopy unless observed from a posteromedial view through the intercondylar notch or through a separate posteromedial portal [
24]. In fact, a large systematic review also demonstrated a trend for negative correlation between reported accuracy of MRI for meniscal lesions and the year of publication [
7]. The purpose of the current study was therefore to add to the body of literature on current accuracy measures specific to 1.5-Tesla MRI of the knee in the adult population relating to the ACL, the menisci and to the articular cartilage and to identify characteristics of false negative lesions. It was hypothesized that MRI accuracy would be between 80 to 90% for the menisci and ACL and substantially lower for the articular cartilage. It was also hypothesized that specific lesion characteristics of the menisci and articular cartilage in addition to patient age would be associated with MRI accuracy.