To evaluate the stiffness of peri-knee muscles in patients with knee osteoarthritis (KOA) using shear wave elastography (SWE) and to analyze its correlation with knee joint function.

This study was conducted at Henan Provincial Luoyang Orthopedic Hospital (Henan Provincial Orthopedic Hospital). Participants included KOA patients and healthy controls. KOA diagnosis was based on the Chinese Guideline for Diagnosis and Treatment of Osteoarthritis (2024 edition) with Kellgren-Lawrence gradesⅠtoⅢ; individuals with conditions or medication history potentially affecting lower limb muscles were excluded. Healthy control group had no relevant history and no strenuous exercise, alcohol, or caffeine intake 48 h prior. Propensity score matching (PSM) was used to balance the two groups. Shear wave elastography was used to assess the elastic modulus, reflecting muscle stiffness, of the quadriceps (vastus medialis, rectus femoris, vastus lateralis), hamstrings (semimembranosus, semitendinosus, biceps femoris long head), and gastrocnemius (medial/lateral heads). KOA patients were assessed using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and knee range of motion (ROM). Pearson or Spearman correlation analysis was performed between muscle stiffness and WOMAC scores/knee ROM.

Compared with healthy group, KOA patients showed increased stiffness in the rectus femoris (Z=–2.45, P=0.014), semimembranosus (Z=–2.15, P=0.032), semitendinosus (Z=–3.97, P<0.001), and biceps femoris long head (Z=–2.49, P=0.013), and the differences were statistically significant. After correction, correlation analysis in KOA patients showed that hamstring stiffness was positively correlated with total WOMAC score and its subscales (pain, stiffness, physical function) and negatively correlated with knee ROM. Specifically, semimembranosus stiffness correlated positively with total WOMAC (r=0.596), pain (r=0.463), stiffness (r=0.478), and physical function (r=0.632) (all P<0.01), and negatively with ROM (r=–0.641, P<0.001). Semitendinosus stiffness correlated positively with total WOMAC (r=0.437), pain (r=0.451), stiffness (r=0.458), and physical function (r=0.420) (all P<0.05), and negatively with ROM (r=–0.507, P<0.01). Biceps femoris long head stiffness correlated positively with total WOMAC (r=0.585), pain (r=0.587), stiffness (r=0.510), and physical function (r=0.547) (all P<0.001), and negatively with ROM (r=–0.485, P<0.01).

Increased hamstring stiffness is associated with worse knee function and reduced ROM in KOA. Targeted intervention on these specific muscles may represent a novel strategy for improving knee function in KOA patients.