The Relationship between Muscle Weakness and Activation of the Cerebral Cortex Early after Unicompartmental Knee Arthroplasty

[Purpose] This study investigated the relationship between muscle weakness and activation of the cerebral cortex in the early period after unicompartmental knee arthroplasty (UKA). [Subjects] The subjects were 11 patients who underwent UKA. [Methods] They performed maximum isometric knee extension using a muscle force measurement device before, and 1 and 2 weeks after UKA. They were simultaneously measured for changes in the concentrations of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin in the bilateral sensorimotor leg areas using functional multi-channel near-infrared spectroscopy. [Results] The muscle force decreased after UKA, and the active region of the sensorimotor leg area also narrowed. The severity of knee pain with muscle contraction 2 weeks after UKA did not change significantly compared with the preoperative level. [Conclusions] The patients treated with UKA displayed early postoperative muscle weakness, and the bilateral sensorimotor areas that were activated during maximum isometric knee extension were narrowed, suggesting that early postoperative muscle weakness is influenced by the central nervous system.