Magnetic resonance (MR) imaging is the most important imaging modality for the evaluation of traumatic or degenerative cartilaginous lesions in the knee. It is a powerful noninvasive tool for detecting such lesions and monitoring the effects of pharmacologic and surgical therapy. The specific MR imaging techniques used for these purposes can be divided into two broad categories according to their usefulness for morphologic or compositional evaluation. To assess the structure of knee cartilage, standard spin-echo (SE) and gradient-recalled echo (GRE) sequences, fast SE sequences, and three-dimensional SE and GRE sequences are available. These techniques allow the detection of morphologic defects in the articular cartilage of the knee and are commonly used in research for semiquantitative and quantitative assessments of cartilage. To evaluate the collagen network and proteoglycan content in the knee cartilage matrix, compositional assessment techniques such as T2 mapping, delayed gadolinium-enhanced MR imaging of cartilage (or dGEMRIC), T1ρ imaging, sodium imaging, and diffusion-weighted imaging are available. These techniques may be used in various combinations and at various magnetic field strengths in clinical and research settings to improve the characterization of changes in cartilage.

The menisci are internal structures that are of central importance for a healthy knee joint; they have a key role in the structural progression of knee osteoarthritis (OA), and the risk of the disease dramatically increases if they are damaged by injury or degenerative processes. Meniscus damage might be considered a signifying feature of incipient OA in middle-aged and elderly people. As approximately every third knee of people in these groups has a damaged meniscus, tears are common incidental findings of knee MRI. However, as most tears do not cause symptoms, careful clinical evaluation is required to determine if a damaged meniscus is likely to directly impact a patient's symptoms. Conservative management of patients with knee pain and a degenerative meniscal tear should be considered as a first-line therapy before surgical treatment is contemplated. Patients with mechanical interference of joint movements, such as painful catching or locking, might need surgical treatment with meniscal repair if possible. In a subset of patients, meniscal resection might relieve pain and other symptoms that potentially originate directly from the torn meniscus. However, the possibility of an increased risk of OA if functional meniscal tissue is removed cannot be overlooked.

Objective To evaluate if two different measures of synovial activation, baseline Hoffa-synovitis and effusion-synovitis, assessed by MRI, predict cartilage loss in the tibiofemoral joint at 30 months follow-up in subjects with neither cartilage damage nor tibiofemoral radiographic osteoarthritis (OA) of the knee. Methods Non-contrast enhanced MRI was performed using proton density-weighted fat-suppressed sequences in the axial and sagittal planes and a STIR sequence in the coronal plane. Hoffa-synovitis, effusion-synovitis and cartilage status were assessed semiquantitatively according to the WORMS scoring system. Included were knees that had neither radiographic OA nor MRI-detected tibio-femoral cartilage damage at the baseline visit. Presence of Hoffa-synovitis was defined as any grade ≥2 (range from 0–3) and effusion-synovitis as any grade ≥2 (range from 0–3). We performed logistic regression to examine the relation of presence of either measure to the risk of cartilage loss at 30 months adjusting for other potential confounders of cartilage loss. Results Of 514 knees included in the analysis, prevalence of Hoffa-synovitis and effusion-synovitis at the baseline visit was 8.4% and 10.3%, respectively. In the multivariable analysis, baseline effusion-synovitis was associated with an increased risk for cartilage loss (odds ratio (OR) = 2.7, 95% confidence intervals 1.4–5.1, p=0.002); however, no such an association was observed for baseline Hoffa-synovitis (OR =1.0, 95% confidence intervals 0.5–2.0). Conclusions Baseline effusion-synovitis, but not Hoffa-synovitis, predicted cartilage loss. Our findings suggest that effusion-synovitis, a reflection of inflammatory activity including joint effusion and synovitic thickening, may play a role in future development of cartilage lesions in knees without OA.