Title : Management and outcomes of spontaneous osteonecrosis / subchondral insufficiency fracture of the knee: A systematic review and limited meta-analysis
Abstract:
Purpose: Spontaneous Osteonecrosis of the Knee (SONK) is increasingly recognised within the spectrum of Subchondral Insufficiency Fracture of the Knee (SIFK), reflecting a shift towards mechanically influenced subchondral failure. This systematic review aimed to comprehensively evaluate outcomes across conservative, pharmacological, joint-preserving and arthroplasty strategies and to identify prognostic factors associated with disease progression and treatment failure.
Methods: A systematic review of 34 studies was performed. Data were extracted for study design, sample size, treatment, follow-up, clinical and radiological outcomes, revision, conversion to arthroplasty, complications and prognostic factors. A limited random-effects meta-analysis of proportions using logit transformation and inverse-variance weighting was conducted for clinically comparable outcomes with extractable event counts and denominators. Methodological quality and risk of bias were assessed according to study design.
Results: Evidence was predominantly derived from retrospective cohorts and case series. Conservative and pharmacological treatments demonstrated symptomatic improvement in selected early-stage disease, while joint-preserving procedures showed favourable native-joint survival in appropriately selected pre-collapse or malaligned knees. Arthroplasty provided reliable outcomes for advanced disease. Pooled failure or conversion to arthroplasty following non-arthroplasty treatment was 11.0% (95% CI 6.0–19.5%; I²=64.9%; 14 studies). Revision or failure following arthroplasty was 5.5% (95% CI 3.1–9.4%; I²=0%; 8 studies), while joint-preservation success following selected procedures was 95.2% (95% CI 90.2–97.7%; I²=0%; 9 studies). Meniscal root/radial tears, meniscal extrusion, varus alignment, older age, lesion characteristics and advanced osteoarthritis were associated with poorer outcomes.
Conclusions: Management should reflect the contemporary subchondral insufficiency fracture paradigm and be individualised according to disease stage, lesion characteristics, meniscal pathology, alignment and compartment involvement. Early diagnosis and offloading are supported for pre-collapse disease, joint preservation is appropriate in selected patients, and arthroplasty remains reliable for advanced disease. Prospective comparative studies using standardised definitions and outcomes are required.
Keywords: Subchondral insufficiency fracture, Spontaneous osteonecrosis, Knee, Joint preservation, Arthroplasty, Systematic review, Meta-analysis.
