Impact of soft tissue around the knee on the efficacy of extracorporeal shockwave therapy in knee osteoarthritis
Authors: Liu Yu , Wu Chunhu , Chen Changsong , Zhang Lianhe , Xing Gengyan , Wu Kun , Zhao Zhe , Geng Huan , Yin Huadong , Hu Xiaohua , Ma Yuhai 
Published: June 2022

Abstract
Background: Knee osteoarthritis (KOA) is the leading cause of knee pain in middle-aged and older individuals. In recent years, extracorporeal shockwave therapy (ESWT) has been applied to treat patients with KOA to reduce pain and improve function. We aimed to determine the association between the distribution of tissue around the knee joint and the efficacy of ESWT in KOA treatment. We were also interested in studying KOA pathogenesis from the perspective of imaging evaluation.Materials and methods: Patients (n=123) diagnosed with KOA who received ESWT were selected to participate in this study, and were grouped according to their body mass index (BMI). The treatment parameters were as follows: 8000 pulses, 2.0 bar, 0.25 mJ/mm2, and 6 Hz/s once per week for 8 weeks. The visual analog scale (VAS), Lequesne index, and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) were measured before and after treatment to assess knee pain and functional recovery in all patients and according to BMI groups. Radiographs were used to measure the richness of the soft tissue around the knee joint. The correlation between the distribution of tissue, pain, and functional improvement was analyzed using the receiver operator characteristic (ROC) curve. The effect of BMI and the distribution of tissue around the knee joint on the efficacy of ESWT treatment in KOA patients were evaluated.Results: A total of 123 patients were enrolled; 59 were in the normal or below normal BMI (<25 kg/m2) category (NBB group) and 64 were classified as overweight and above (BMI ≥ 25 kg/m2) (OAB group). All the patients showed a reduction in pain after treatment compared to that before treatment (P <0.01). As measured by VAS, after the intervention, pain in the OAB group decreased to a greater extent than that in the NBB group (P < 0.01). As measured by the Lequesne and WOMAC indexes, after the intervention, the functional index of the OAB group improved to a greater extent than that of the NBB group (P < 0.01). We determined through the area under the curve (AUC) that, with VAS as the demarcation criterion, when the tibial plateau soft tissue ratio (TPSTR), femoral intercondylar apex soft tissue ratio (FIASTR), and medial tibial soft tissue ratio (MTSTR) exceeded 1.538, 1.534, and 1.296, respectively, the patient's pain relief was more pronounced the ESWT treatment was better. With pain in WOMAC as the demarcation criterion, the TPSTR, FIASTR, and MTSTR also are positively correlated with pain relief in patients. When the Lequesne and WOMAC scores were the demarcation criteria, the patients' function improved significantly when the the patella apical soft tissue ratio (PASTR) exceeded 2.401 and 2.635, respectively. Conclusion: ESWT can effectively alleviate pain and improve knee function in patients with KOA, and the efficacy of ESWT is closely related to the abundance around the knee joint; the soft tissue around the knee joint should also be an important reference factor and the focus of research in KOA treatment.