Background: Tendon mechanical properties have been used to evaluate the effects of therapies on the healing of animal tendons, but these measures have not been convenient to record in vivo in humans due to their invasive nature. The aims of this study were to assess the capability of an ultrasonography technique to track the change in stiffness of the healing human patellar tendon and to assess the correlation between stiffness parameters and clinical recovery measurements.Method: Ten subjects undergoing anterior cruciate ligament reconstruction with a patellar tendon autograft were recruited for the study as well as 10 healthy control subjects. The surgical tendons' mechanical properties were evaluated at 2 and 6 months after surgery with a two-scan ultrasonography technique. A paired sign-rank test was performed to compare the change in biomechanical parameters and clinical recovery measurements across time between surgical and control groups.Results: Tendon stiffness of the surgical group increased from ~71% to ~94% when compared to the stiffness of the contralateral tendons at the first visit; however, the difference was not significant (P = 0.18). Significant improvements were shown in all the clinical recovery outcomes. Poor correlation was found between the clinical recovery measurements and tendon stiffness.Conclusions: No significant change in patellar tendon stiffness with healing was detected over the 2–6 month period after surgery, suggesting the tendon stiffness recovery in humans proceeds more slowly than other clinical measures.