AbstractPurposeMedial tibial stress syndrome (MTSS) represents a common diagnosis in individuals exposed to repetitive high‐stress loads affecting the lower limb, e.g., high‐performance athletes. However, the diagnostic approach and therapeutic regimens are not well established.MethodsNine patients, diagnosed as MTSS, were analyzed by a comprehensive skeletal analysis including laboratory bone turnover parameters, dual‐energy X‐Ray absorptiometry (DXA), and high‐resolution peripheral quantitative computed tomography (HR‐pQCT).ResultsIn 4/9 patients, bilateral pseudofractures were detected in the mid‐shaft tibia. These patients had significantly lower levels of 25‐hydroxycholecalciferol compared to patients with MTSS but similar levels of bone turnover parameters. Interestingly, the skeletal assessment revealed significantly higher bone mineral density (BMD) Z‐scores at the hip (1.3 ± 0.6 vs. − 0.7 ± 0.5, p = 0.013) in patients with pseudofractures and a trend towards higher bone microarchitecture parameters measured by HR‐pQCT at the distal tibia. Vitamin D supplementation restored the calcium‐homeostasis in all patients. Combined with weight‐bearing as tolerated, pseudofractures healed in all patients and return to competition was achieved.ConclusionIn conclusion, deficient vitamin D levels may lead to pseudofractures due to localized deterioration of mineralization, representing a pivotal component of MTSS in athletes with increased repetitive mechanical loading of the lower limbs. Moreover, the manifestation of pseudofractures is not a consequence of an altered BMD nor microarchitecture but appears in patients with exercise‐induced BMD increase in combination with reduced 25‐OH‐D levels. The screening of MTSS patients for pseudofractures is crucial for the initiation of an appropriate treatment such as vitamin D supplementation to prevent a prolonged course of healing or recurrence.Level of evidenceIII.