Prognostic factors of progression of osteoarthritis of the knee: A systematic review of observational studies

Objective To provide an overview of prognostic factors of knee osteoarthritis (OA) progression. Methods We searched Medline and Embase up to December 2003 according to a specified search strategy (keywords for disease, location, and study design). Studies that fulfilled predefined criteria were assessed for methodologic quality. Study characteristics and associations were extracted and the results were summarized according to a best evidence synthesis. Results Of the 1,004 studies found, 37 met the inclusion criteria. Methodologic quality was assessed and only high‐quality studies were included (n = 36). The best evidence synthesis yielded strong evidence that hyaluronic acid serum levels and generalized OA are predictive for progression of knee OA. Sex, knee pain, radiologic severity, knee injury, quadriceps strength, and regular sport activities were not predictive. Conflicting evidence for associations was found for several factors including body mass index and age. Limited evidence for an association with progression of knee OA was found for several factors, including the alignment (varus/valgus) of the joint. Limited evidence for no association with progression of OA was also found for several factors, including meniscectomy, several markers of bone or cartilage turnover, and the clinical diagnosis of localized OA. Conclusion Generalized OA and level of hyaluronic acid seem to be associated with the radiologic progression of knee OA. Knee pain, radiologic severity at baseline, sex, quadriceps strength, knee injury, and regular sport activities seem not to be related. For other factors, the evidence was limited or conflicting.