Fig. 2From: Serum hyaluronic acid concentration predicts the progression of joint space narrowing in normal knees and established knee osteoarthritis – a five-year prospective cohort studyConcentration of serum hyaluronic acid by Kellgren–Lawrence (KL) grade. P values <0.05 were found compared with *KL grade 0, †grade 1, ‡grade 2, and #grade 3Back to article page