Pharmacokinetic analysis of BMP-7 in cartilage tissue. (a) Outline for the analysis. Cartilage was obtained from knee joints at 1 hour and 1, 2, 4, and 7 days after intra-articular injection of 500 ng BMP-7 or phosphate-buffered saline. Three joints for each time point were investigated. (b) BMP-7 concentration per cartilage wet weight (ng/g). The values are shown as average ± standard deviation. BMP, bone morphogenetic protein.