Watabe Takaya, Nishikawa Yuichi, Naito Hisashi, Sengoku Takuya, Taniguchi Yuta
Section of Rehabilitation, Kanazawa University Hospital, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan.
Institute of Science & Engineering, Kanazawa University, Kakuma-Machi, Kanazawa, Ishikawa, 920-1192, Japan.
Ann Biomed Eng. 2025 Jul 17. doi: 10.1007/s10439-025-03802-2.
While changes in muscle quality and quantity are common concerns as knee osteoarthritis (KOA) progresses, it is equally important to consider the central nervous system's role in regulating muscle force output. This study aimed to elucidate the firing properties of motor units (MUs), muscle quantity, and muscle quality during submaximal isometric contractions in patients with early and severe KOA.
This was a prospective study comparing 30 patients with KOA according to the Kellgren/Lawrence grading system divided into early and severe KOA groups. The participants performed ramp-up and sustained contractions at 10%, 30%, and 60% of their maximal voluntary contraction (MVC). High-density surface electromyography signals were recorded in the vastus medialis (VM) and vastus lateralis (VL) muscles on the affected side. Skeletal muscle quantity and quality were assessed using computed tomography based on cross-sectional area (CSA) and computed tomography attenuation value (CTV), respectively.
The CSA of the VM muscle was significantly smaller in the severe KOA group than in the early KOA group (p = 0.021). A total of 682 MUs were detected (early KOA, n = 348, severe KOA, n = 334). The ramp-down phase of the discharge rate (DR) of MUs recruited by the VL muscle in the severe KOA group was significantly lower than that in the early KOA group (p = 0.004). In addition, the knee extension torque of patients with early KOA was significantly correlated with the CSA of the VM muscle (r = 0.405) and the DR obtained at 30% MVC of the VM (r = 0.503) and VL (r = 0.610) muscle. Furthermore, the knee extension torque in patients with severe KOA was significantly correlated with the CTV of the VM (r = 0.677) and VL (r = 0.599) muscles.
In patients with severe KOA, a small CSA of the VM is associated with a characteristic DR pattern depending on the contraction level. The VM and VL muscles fired without a hierarchical pattern in the early and severe KOA groups. These findings suggest that neuromuscular degeneration may occur not only in patients with severe KOA but also in patients with early KOA.
随着膝关节骨关节炎（KOA）的进展，肌肉质量和数量的变化是常见的关注点，同样重要的是要考虑中枢神经系统在调节肌肉力量输出中的作用。本研究旨在阐明早期和重度KOA患者在次最大等长收缩过程中运动单位（MU）的放电特性、肌肉数量和肌肉质量。
这是一项前瞻性研究，根据Kellgren/Lawrence分级系统将30例KOA患者分为早期和重度KOA组进行比较。参与者在其最大自主收缩（MVC）的10%、30%和60%水平进行渐增和持续收缩。在患侧的股内侧肌（VM）和股外侧肌（VL）记录高密度表面肌电图信号。分别基于横截面积（CSA）和计算机断层扫描衰减值（CTV），使用计算机断层扫描评估骨骼肌数量和质量。
重度KOA组VM肌肉的CSA显著小于早期KOA组（p = 0.021）。共检测到682个运动单位（早期KOA组，n = 348；重度KOA组，n = 334）。重度KOA组中由VL肌肉募集的运动单位放电率（DR）的下降阶段显著低于早期KOA组（p = 0.004）。此外，早期KOA患者的膝关节伸展扭矩与VM肌肉的CSA（r = 0.405）以及VM（r = 0.503）和VL（r = 0.610）肌肉在30%MVC时获得的DR显著相关。此外，重度KOA患者的膝关节伸展扭矩与VM（r = 0.677）和VL（r = 0.599）肌肉的CTV显著相关。
在重度KOA患者中，VM较小的CSA与取决于收缩水平的特征性DR模式相关。在早期和重度KOA组中，VM和VL肌肉的放电没有分层模式。这些发现表明，神经肌肉退变不仅可能发生在重度KOA患者中，也可能发生在早期KOA患者中。
