Abstract
ABSTRACT
Background
Intramuscular fat infiltration (IMFI) is considered to be closely associated with knee osteoarthritis (KOA); however, its overall association, muscle‐specific involvement, and clinical relevance remain unclear.
Objective
To quantify the association between IMFI and KOA, identify affected muscle groups, and evaluate prognostic value.
Methods
We searched PubMed, Web of Science, Scopus, and Embase up to December 2025 for observational studies. Two reviewers independently screened, extracted data, and assessed bias (NOS/JBI). Pooled standardized mean differences (SMDs) were calculated using random‐effects models, with subgroup and sensitivity analyses.
Results
Seventeen studies were included. IMFI was significantly higher in KOA patients than controls (SMD = 0.63, 95% CI 0.41–0.85,
I
2
= 84.7%). Anatomically, the anterior thigh muscles (rectus femoris, vastus lateralis, vastus medialis) demonstrated a significant pooled effect (SMD = 0.96, 95% CI 0.66–1.25,
I
2
= 3.2%) and showed the strongest pooled association, whereas posterior, medial, and composite measures did not demonstrate significant associations. At the individual muscle level, a single study reported a notable association for the semimembranosus (SMD = 1.25, 95% CI 0.57–1.93); however, this finding is based on limited evidence and requires confirmation in future studies. Subgroup by imaging modality: CT demonstrated a significant association (SMD = 0.59, 95% CI 0.28–0.90), while MRI and ultrasound did not show significant associations. Elevated IMFI was also associated with reduced muscle strength, higher KOA incidence, structural progression, and increased knee replacement risk.
Conclusion
A moderate positive association exists between IMFI and KOA, with notable muscle‐specific heterogeneity. Anterior thigh muscles show the strongest pooled association, whereas individual muscle findings require further confirmation. These findings suggest that IMFI may represent a promising potential marker warranting further prospective investigation for risk stratification, though causality and its role in modifying disease progression remain to be established.