In this trial involving 60 participants, it was found that compared with traditional rehabilitation treatment focusing on the quadriceps femoris, a 12-week rehabilitation intervention of combined hip and knee exercises after surgery can improve the therapeutic effect of TKA and accelerate postoperative rehabilitation by improving the function of the affected limbs, accelerating the recovery of walking and climbing and improving the gait of the knee joint after TKA. The effect of combined hip and knee exercises was positively correlated with the increase in exercise load.
As one of the most commonly used scales to evaluate the function of the lower extremities, the WOMAC is confirmed to be effective, reliable and sensitive when applied to Chinese OA patients.[19, 20] Through the WOMAC scale we found that combined strengthening of the hip and knee joints as a means of postoperative rehabilitation was helpful for improving the curative effect of TKA (p༜0.05) and accelerate the recovery of postoperative function (p༜0.05). Meanwhile, the FJS-12 has been proven to have a strong correlation with the traditional WOMAC and other osteoarthritis score[21–23], but most of the subjects were evaluated with the FJS-12 score after more than one year postoperatively.[22, 24] This is because this scale cannot reach the plateau period to evaluate the curative effect until more than one year after the operation. In this study, different rehabilitation treatments led to different surgical effects (F = 49.232, p < 0.05) and rehabilitation effects (F = 116.604, p < 0.05) in WOMAC, but there were no significant differences among different treatment groups (F = 1.499, p > 0.05) in FJS-12. This result is consistent with the conclusion of the "floor effect" of FJS-12 in previous research.[25–27]
Contrary to what we initially hypothesized, the application of early combined hip and knee strengthening exercises did not effectively improve knee pain. A review of the study found that we did not control for or detail the frequency and dose of oral or topical painkillers in different groups, so we speculate that the VAS scores recorded during the last follow-up do not fully reflect the true knee joint pain levels. Additionally, the exercise intensity and resistance of the rehabilitation exercises in the three treatment groups were different, and the resulting differences in muscle fatigue and pain adaptability also affected the effectiveness of the VAS scores.
Through linear correlation matrix mapping of the statistical data, we found that the correlations of WOMAC with quadriceps femoris and hip abductor muscle strength were r=-0.181 and r=-0.196, respectively, indicating that the WOMAC decreased with increasing quadriceps femoris and hip abductor muscle strength, and the lower the WOMAC score was, the better the knee joint function. Therefore, the prognosis and functional rehabilitation of patients after TKA are closely related to the strengths of the quadriceps femoris and abductor muscles of the hip; this is in agreement with the results of Piva's observational study, which revealed correlations of the strengths of the quadriceps femoris (r=-0.194) and abductor muscles of the hip (r=-0.247) and WOMAC. Improving muscle strength and lower limb function through exercise interventions also helps demonstrate that combined hip and knee exercises can improve the prognosis and accelerate the functional rehabilitation of patients after TKA.
The conclusion of this study is similar to that of a small preparatory experiment conducted by Harikesavan et al., in which specialized training of the hip abductor could help improve the strength of the hip abductor muscles; in the experimental group, the specialized training of the hip abductor significantly improved the results of the one-leg standing test and 6-min walking test. However, the research by Schache et al. reached the opposite conclusion. During the exercise intervention, Schache did not effectively establish separate experimental and control groups and did not unify the training regimen across different rehabilitation trainers, which may have had some impact on the effectiveness of the rehabilitation guidance. In addition, the opposite conclusions of Schache and Harikesavan may also be related to the large differences in the intensity of the hip abductor exercises. Kwangsun also believes that hip exercises performed through a 12-week exercise intervention can improve the function and gait of patients after TKA, but the participants in his study were all discharged from the hospital within one year after TKA, which goes beyond the scope of rapid recovery. During the intervention, it is difficult to exercise the hip joint alone, and the related instruments are not used to quantitatively measure the changes in muscle strength.
There are still some shortcomings in this study. Firstly, this study failed to record the oral or external application of painkillers during exercise and rehabilitation, which became a potential factor to reduce the authenticity and effectiveness of VAS. Secondly, we underestimated the floor effect of FJS-12, which made the scale unreliable in this study.