Knee osteoarthritis (KOA) increases in prevalence with age, with the knee being a major weight-bearing joint1. KOA usually manifests with stiffness and chronic pain at the knee joint, which limits mobility, reduces quality of life, and increases the risk of cardiovascular disease2. Diabetes mellitus, which is also related to age, contributes to the risk of KOA development, as elevated glucose and lipids levels promote advanced glycation end product (AGE) formation, leading to chronic joint inflammation and cartilage degeneration3. Despite the availability of healthcare services, two in five Malaysians with diabetes mellitus are unaware of their diagnosis, while 56% of those diagnosed failed to maintain good blood sugar control4. Acute hyperglycemia could lead to a hyperglycemic hyperosmolar state, which is life-threatening, while chronic hyperglycemia leads to peripheral neuropathy, nephropathy, retinopathy, and cardiovascular disease5.
Peripheral neuropathy, which is a microvascular complication resulting from poor glycemic control and leads to altered pain mechanisms, may exaggerate knee pain in KOA6. The presence of diabetes in individuals with KOA is associated with a reduced range of movement at the knee joint, reduced knee function, increased radiographic changes, and poorer quality of life7. The reduced physical performance resulting from the effects of diabetes on KOA is characterized by impaired muscle strength and coordination8. Magnetic resonance imaging evidence of degenerative changes associated with cartilaginous and meniscal damage, such as reduced joint space and malalignment, appears to be more severe in individuals with diabetes9.
Poor glycemic control is linked to upregulated degenerative enzymes and inflammatory factors in knee synovial fluid. Elevated cytokines and proteins in diabetes, such as IL-1β, IL-4, IL-6, nuclear factor-κB (NF-κB), and tumor necrosis factor-alpha (TNF-α), are associated with KOA pathophysiology10,11. While in the chondrocytes, defective glucose transporter leads to upregulated glycolysis, polyol pathways, protein kinase C and pentose pathways, and eventually high production of reactive oxygen species10.
Fasting and random blood glucose provide an estimation of current glycemic status as well as glucose-handling ability related to insulin resistance12. Glycated hemoglobin A (HbA1c) is a measure of glycemic control over the past three months. This does not, however, provide details of acute fluctuations13. Capillary blood glucose testing provides immediate assessments of glycemic status at the bedside or clinic, which has led to debates on their value in determining glycemic control as well as predicting the risk of complications14,15. Thus, this study aims to elucidate the association between glycemic control determined with HbA1c and elevated blood glucose determined with capillary blood glucose (CBG) with the Knee Injury and Osteoarthritis Outcome Scores (KOOS), physical performance, physical activity level, radiographic severity and inflammatory markers in individuals with KOA.