To our knowledge, there are few studies focusing on the prediction of the progression of knee OA. In this study, the most important finding is that, a larger onset age, BMI, JLCA0, kMPTA and kJLCA is associated with a shorter remaining life of knee joint and greater risk of requiring TKA. Changes of MPTA and JLCA indicate knee varus deformity and narrowing of knee compartments. The rates of change in MPTA and JLCA calculated in this clinical study are the average value between the periods of arthritis onset and TKA; and the clinical importance of this prediction model is to provide early detection and health guidance for patients with knee OA, which is of great significance in reducing utilization rate of TKA. When patients are regularly followed up, X-rays are routinely used and corresponding values could be measured; meanwhile, we register their basic information. The values of two times follow-up are completely obtained and substituted into the prediction model in this topic, so as to distinguish between patients with rapid and slow progression of knee OA; then, individualized and targeted guidance and treatment could be implemented.
Here, we proposed the use of several indexes for prediction of disease progression and remaining life of knee joint; our model was confirmed to be effective and reliable. From the statistical verification results of standardized coefficient, kMPTA and kJLCA play the main roles in the prediction model (standardized coefficient B is 0.3 and 0.3, respectively). Besides, X-rays were used to calculate the rates of change in the medial proximal tibial angle and the joint line convergence angle; this procedure is economical, convenient and time-saving, which could be related to a better patients’ compliance.
Patients’ compliance is determined by many factors. Previous studies have shown that willingness to consider joint replacement, socioeconomic status, general health status, arthritis severity, educational level, age, and sex are important factors determining the utilization rate of TKA[9–11]. Willingness to consider joint replacement appears to be the most dominant factor associated with utilization of TKA; low socioeconomic status, poor general health status, low educational level, and female sex are associated with low TKA utilization rates. Therefore, delaying OA progression and reducing the need for TKA are important but challenging issues. Defining the maximum remaining life of knee joint (i.e., the risk of TKA and residual life of knee joints) will help to improve patient awareness and compliance, and prevent the increased need for TKA via early medical intervention, which helps to reduce the social costs of severe knee OA. From this point, calculating the exact remaining life of the knee joint is not the most important, but through this way to make patients aware of the severity of OA and actively cooperate with individual preventive measures to slow down the progression of OA and reduce the demand for TKA. When patients with high risk of requiring TKA are differentiated from patients with mild knee OA by onset age, BMI, JLCA0, kMPTA and kJLCA in this prediction model, early individualized medical intervention (e.g., weight loss, personalized exercise, and knee-preserving surgery) could enable postponement or prevention of TKA.
Knee OA therapy demands a strategy that specialists agree with in considering the clinical symptoms and the disease severity. Conservative strategy is divided into pharmacological and non‑pharmacological approaches. Studies showed that, losing weight means a decrease of the pressure on the knee joint, improving physical function and biomechanics; a decrease in weight of 1 kilogram could produce quadruple reduction of the forces acting on the knee[17]. For subjects with OA symptoms, relief of symptoms has often been observed through weight loss and physical strengthening exercises only[8]. Non-steroidal anti-inflammatory drugs (NSAIDs), proprotracyclines, steroids, hyaluronic acid and platelet-rich plasma et al. could be chosen in pharmacologic strategy. Conservative and noninvasive strategy can be discussed in patients with mild knee symptoms or a slow progression. If patients in the follow-up are in a stage of rapid progress from mild OA, an invasive medical knee joint preservation strategy should be considered. Arthroscopic lavage and debridement and osteotomy around the knee are often identified as a treatment option. This phased treatment strategy, which relies on identifying people with rapid progress, is not clear; a complete strategy needs to be refined by further research, and the results of this study can play an important role in the identification and classification of at-risk populations.
The data presented here are clinically advanced in the following three respects. First, X-ray examination is economical and convenient, greatly improving the rates of patient examination and re-examination; this facilitates knee OA evaluation based on dynamic changes. Second, all patients enrolled in this study had TKA indications, such as K-L grade IV, severe pain, severe limitation of activity, and poor quality of life. However, they had been treated with TKA, thus avoiding some bias (e.g., low rate of TKA utilization because of low socioeconomic status, poor general health status, and/or low educational level). Third, risk of requiring TKA can be shown intuitively by this mathematical model which helps us to identify patients with rapidly aggravated knee OA and intuitive and pellucid result is helpful to improve patients' compliance by improving their understanding of knee OA and TKA. Early medical intervention will be carried out strictly for these patients to delay the progress of OA.
This study had several limitations. First, patients without records of TKA after the longest follow-up period in this study were excluded; this ensured that the study focused only on TKA risk, rather than the threshold for determining whether TKA surgery will be performed in the future. Therefore, additional systematic studies are required. Second, retrospective research can explore correlations in data and build a correlation model based on random sampling. However, to make the predictive model more convincing, additional prospective studies are needed to verify its sensitivity and reliability by comparing differences between theoretical and actual values. Third, although the total amount of data was large, a small amount of data met our study criteria, reflecting incomplete follow-up because of patient concerns regarding X-rays or a lack of appropriate understanding concerning the seriousness of knee OA.