Bone repair is controlled by signalling proteins as well as mechanical stimuli. Bone morphogenetic proteins (BMPs), implanted or injected into a fracture site, can enhance bone healing, and so can mechanical stimulation. Possibly, mechanical signals can alter BMP expression, but furthermore, tissue differentiation initiated by an implanted BMP could be guided into the required direction by mechanical signals. Mechanical stimulation also has profound effects on tendon repair. We studied the effects of 3 different BMPs in a rat tendon repair model. One of these, osteogenic protein 1 (OP‐1) induced bone formation in the tendon at the expense of mechanical strength and thus overrode any mechanical control system. On the other hand, cartilage derived morphogenetic protein 1 and 2 (CDMP‐1 and ‐2) both made the tendon callus bigger and stronger at an early time point.