Osteoarthritis (OA) is a chronic joint disease that is highly prevalent worldwide and a whole joint disease involving all joint tissues such as menisci, subchondral bone, infrapatellar fat pad and synovial membrane (1, 2). The 2015 World Health Organization Global Report on Aging and Health highlights OA as the leading cause of disability in adults aged more than 60 (3–5). Globally, the proportion of joint-related disability due to OA increased by 114.5% from 1990 to 2019. Given the aggravating trend of global population aging and the continued increase in the prevalence of OA, global healthcare expenditure is also expected to be huge in the future (6, 7).

The most common positions affected by OA are the hip, knee and hand. The knee is the most frequently affected joint, and knee OA is associated with excessive joint loading and injury (8, 9). X-ray radiography is frequently used for the diagnosis of OA, but x-ray is an indirect and insensitive way of detecting osteoarticular cartilage (10). Arthroscopy, although a reliable and sensitive method, is an invasive technique (11). Magnetic resonance imaging (MRI) is a non-invasive method that provides multiplanar imaging, and excellent soft tissue contrast, however, it is expensive and time consuming (12). Ultrasound (US) is a reliable tool for assessing the integrity and thickness of articular cartilage. Its advantages include being inexpensive, non-invasive, rapid and easily accessible (13).

Ultrasonic shear wave elastography (SWE) is a recently developed technique that is based on the measurement of shear wave velocity generated by ultrasound pulses (13). The technique can be used to assess tissue elasticity. SWE was first applied in breast lesions and thyroid gland lesions, and was subsequently used to assess liver fibrosis (14). More recently, SWE has also been used to assess the mechanical properties of musculoskeletal tissues (12). The SWE technique identifies differences in stiffness between tissues, which is a good indicator of damage to articular cartilage.

Although elastic ultrasound has been previously reported to be useful in the diagnosis of OA (11, 13), there is limited research on the effective indicators of OA diagnosis in SWE and their risk factors, so we conducted this study.

Based on the presence or absence of OA, we analyzed the baseline data. As shown in Table 1, there were differences between the two groups in age, gender, BMI, and smoking and alcohol, MMPD and MME. While there was no difference in hypertension and diabetes (Table 1).

Using the Q1 group as a reference, we performed stepwise logistic regression (Table 2) to analyze whether the risk of OA changed with increasing SWE indicators in the Q2–Q4 groups. It can be seen in model 1, when only MMPD was used as the independent variable, there was a positive correlation dose–response relationship between this value and OA (trend p < 0.05) and the OR for Q4 was much greater than 1, [OR = 5.97, 95% CI (2.81, 4.98)], implying that the higher the level of MMPD, the higher the probability of having OA.

Model 2 was constructed after demographic data were included as covariates and a positive correlation dose–response relationship remained. Model 3 had a positive correlation between high levels of MMPD and OA after lifestyle habits were put into the model [OR = 4.12, 95% CI (2.58, 6.58)], but there was no longer a dose–response relationship (Table 2). Model 4 also showed a positive association between high levels of MMPD and OA [OR = 2.12, 95% CI (1.53, 3.95)] after incorporating history of illness.

We also performed an analysis of MME and OA, which showed a dose–response relationship for all models 1 to 4 (trend p < 0.05). Moreover, with the gradual inclusion of the variables, the ORs increased minutely, reaching an OR of 8.98 [OR = 8.98, 95% CI (3.89, 11.52)] for Q4 in model 4 (Table 3).

In addition to analysing the relationship between elastic ultrasound measurements and OA, we also analyzed the relationship between the included covariates and OA. As shown in Figure 1, the risk of OA was significantly higher in the older age group [1.11, 95% CI (1.01, 1.25)] and the risk of diagnosing OA was high in the high BMI group [1.8, 95% CI (1.23, 3.01)] (Figure 3).

In this study, we assessed knee OA lesions by using two metrics including MMPD and MME. We found that the correlation between the two measurements for assessing knee OA was high. Subsequently, exploring the factors influencing the SWE measurement of OA, people with advanced age and high BMI had a higher probability of being diagnosed with OA.

MME is strongly associated with knee OA and meniscal tears, which have also been described as radial displacement of the medial meniscus or medial radial displacement of the medial meniscus (16). Longitudinal studies have shown that the value of MME increases with increasing Kellgren/Lawrence radiological degrees in both supine and standing assessments of the knee (17). Similarly, studies have confirmed a significant correlation between an MME greater than or equal to 3 mm on MRI and an increase in the severity of cartilage damage, and a close association between MME and joint space narrowing (18). MME has been shown to be an independent predictor of disease progression in OA and is strongly associated with tibial and femoral cartilage loss (19).

However, there are limited studies on MMPD for the diagnosis of OA, and our study also supports the validity of MMPD for the diagnosis and prediction of OA, which needs to be confirmed by more relevant studies.

Previous reports have stated that there is a significant correlation between age and tendon, muscle and joint stiffness (20–22). This study also found a significant correlation between age and OA, while the correlation between degeneration and stiffness was equally significant. In moderate to severe OA, the meniscal matrix showed severe fibrocartilage detachment and extensive wear and tear, with reduced cellularity and cellular hypertrophy. Degeneration of the meniscus in OA is also found in people with high BMI, as evidenced by the accumulation of meniscal proteoglycans (23–25). These micro and macro changes in the degenerative meniscus are reflected by increased tissue elastic stiffness values measured by SWE (26, 27). Several previous researches supported that shear wave elastography can serve as an adjunctive tool to aid in the assessment of knee meniscal elasticity, especially can detect meniscus pathologies that may develop due to obesity and aging (28–30). These findings were totally consistent with ours. Ultrasound evaluation with SWE is an easily accessible, inexpensive imaging modality that also provides real-time dynamic evaluation and guides percutaneous interventional procedures. However, evaluation of the meniscus by ultrasound and SWE may be technically difficult due to adjacent bone and ligamentous structures and narrowing of the joint space due to degenerative disease (31).

In conclusion, these preliminary findings suggest that MME and MMPD correlate with the degree of meniscal degeneration, which is seen to reflect knee OA lesions. So, it is reasonable to assume that SWE could be used as a potential tool for assessing OA, especially in aging and high BMI people.

There are several limitations of this study. Firstly, the sample size was small, which reduced the reliability and validity. Secondly, there was a lack of low-age samples. Thirdly, this study only involved measurements of the medial meniscus of the knee and lacked values for the lateral meniscus and other joint measurements. Further studies are needed to improve the reliability of our findings.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by this study were approved by the Ethics Committee from the Third Affiliated Hospital of Hebei Medical University (No. 1354064). The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

JZ: Data curation, Formal analysis, Investigation, Writing – original draft. XZ: Methodology, Software, Writing – original draft. YZ: Conceptualization, Formal analysis, Methodology, Validation, Writing – review & editing.