Evaluation of skeletal muscle metabolism during walking in symptomatic and asymptomatic patients with osteoarthritis of the knee joint using positron emission tomography.

Background: This study aimed to evaluate skeletal muscle metabolism during walking in symptomatic and asymptomatic patients with knee osteoarthritis using positron emission tomography-computed tomography with 18F-fluorodeoxyglucose. We hypothesized that quadriceps muscle metabolism during walking would vary between the groups.

Methods: Twenty-two participants (11 males and 11 females) with knee osteoarthritis (Kellgren-Lawrence grade 2) were divided into symptomatic and asymptomatic groups. The participants performed two 10-min walks on a treadmill, received an intravenous injection of 18F-fluorodeoxyglucose between sets, and underwent positron emission tomography-computed tomography. Regions of interest were manually segmented into 35 skeletal muscles from the pelvis to the foot. The standardized uptake value was calculated to quantitatively examine 18F-fluorodeoxyglucose uptake by muscle tissue.

Results: The mean standardized uptake values of the hip abductor and external rotator muscles were lower in the symptomatic group than in the asymptomatic group and displayed a medium effect size (gluteus medius, P = 0.281; d = 0.482; gluteus minimus, P = 0.079; d = 0.793; piriformis, P = 0.184; d = 0.622). Although the vastus medialis demonstrated a medium effect size (P = 0.191; d = 0.597), the rectus femoris (P = 0.454; d = 0.299), vastus lateralis (P = 0.303; d = 0.392), and vastus intermedius (P = 0.300; d = 0.434) demonstrated no significant differences and only small effect sizes. Therefore, no overall difference in quadriceps muscle metabolism was observed between the groups.

Conclusion: A trend towards lower hip abductor and external rotator muscle metabolism was observed in patients with symptomatic knee osteoarthritis, suggesting that muscle metabolism may be associated with knee symptoms.