a, Schematic depicting the distal femur of a mouse and its major tissue layers before and after MF surgery. b, Representative flow cytometry analysis of the articular surface (top), the periosteum (middle), and bone (bottom) with relative populations of mOP, mCP, mBCSP, and mSSC. c, Quantification of mSSC/million events in bone, cartilage, and periosteum. Graph shows mean + /- s.e.m. Ordinary one-way ANOVA test with post-hoc analysis using Šídák method to compare between specific means. Exact P values to 2 significant figures. (n = 5 mice per group). d, Quantification of mSSC/million events comparing MF joints and joints with articular cartilage and periosteum removed prior to MF surgery (mMF). (n = 5 mice per group). e, Alcian blue staining of mSSC following chondrogenic differentiation with treatment of PBS or BMP2 + sVEGFR1. Scale bars 100μm. Representative of three independent experiments. f, Quantification of the Alcian blue stain after extraction and photometric measurement at OD595. Unless otherwise stated, graphs show mean + /- s.e.m. Two-tailed Student’s t-test. Exact P values to 2 significant figures.