Medial tibial subchondral bone is the key target for extracorporeal shockwave therapy in early osteoarthritis of the knee.

Extracorporeal shockwave therapy (ESWT) is a new non-invasive method to induce tissue regeneration and repair the damaged osteoarthritis (OA) of knee. Previous studies suggested subchondral bone as the key target for OA treatment. However, the relationship of the effect and different locations of subchondral bone is unknown. The purpose of the study was to investigate whether the subchondral bone of medial tibia as the target for ESWT in early OA knee treatment and compared with various locations on lateral tibia and femur condyles. Application of ESWT on the medial tibial subchondral bone ameliorated 38% in gross pathological OA changes (compared to OA, P < 0.001), 94 % in OARSI score (compared to OA, P < 0.001) and 45% in cartilage defect (compared to OA, P < 0.001), 17% in bone mineral density (compared to OA, P < 0.001) than lateral tibia and femur. In micro-CT analysis, ESWT on medial tibial subchondral bone increased bone volume (61% vs 44% in tibia and 62% vs 53% in femur, P < 0.05), yield stress (6 MPa vs 4 MPa in tibia and 4 MPa vs 2 MPa in femur, P < 0.05) and decreased bone porosity (38% vs 53% in tibia and 37% vs 46% in femur, P < 0.05) than OA. The TUNEL, PCNA and osteocalcin significantly influenced the levels of molecular expression in different locations of ESWT application. Our results confirm that application of ESWT to the medial tibial subchondral bone has more effective therapy for OA knee than lateral locations of joint knee.