(a,b) Representative 3D reconstructions of the murine femur using microcomputed tomography (microCT). (c) Femoral length or (d) femoral width at mid-diaphysis, presented as mean ± s.d. with n = 8–20 bones per age per genotype. *p<0.05, **p<0.005, or ***p<0.0005 vs. age-matched Bmp2 Prx1-cKO cohort. (e,g) Representative toluidine blue histology at the mid-diaphysis of the forelimb. (f,h) MicroCT analysis of total cross-sectional bone tissue area presented as mean ±s.d. with n = 4. *p>0.05. (i,j) Cross-sectional composition of cortical bone in the radius of newborn (n = 6–9 per genotype) or 2 week-old mice (n = 3–9 per genotype) (see Materials and methods). Abbreviations: PC, perichondrium; PO, periosteum. (k,l,m) Representative toluidine blue histology at the mid-diaphysis of indicated skeletal elements. (n) Length or (o) width of embryonic day 15 metatarsals, measured following 1 or 5 days of ex vivo culture. Mean ±s.d. with n = 6–12 where **p<0.005, ***p<0.005, or ****p<0.00005. (p,q,r) Femur width mean ±s.d. with n = 6–12 where *p<0.05. (s) Minimum moment of inertia in P14 femur, calculated by microCT (n = 4) shown as mean ±s.d. where ***p<0.0005. (t) Toludine blue histology revealing cortical microcracks in the humerus of Bmp2 Prx1-cKO mice at 4 weeks of age. (u) X-ray images showing representative bowing of the radius and ulna of Bmp2 Prx1-cKO mice in the absence of frank fractures. Statistical analyses were performed using two-tailed Student’s t-test.