Shame over tooth loss: between psychological suffering and structural inequality in Chilean oral health.

Running is a fundamental human locomotion pattern, but it imposes significant biomechanical loads on the lower extremities, with peak vertical ground reaction forces (vGRF) often exceeding 2.5 times body weight during the stance phase. Despite its benefits, running-related injuries are common, affecting millions each year, and their prevalence varies widely, ranging from 3% to 85%. The anterior cruciate ligament (ACL) is among the most frequently injured ligaments, with an estimated incidence of 35 to 85 per 100,000 person-years in active populations. While ACL reconstruction (ACLR) is the standard surgical method for restoring knee stability, it does not guarantee a return to pre-injury biomechanical function. For instance, a systematic review shows that only 55–65% of athletes return to their pre-injury sport level, and reinjury rates can reach 20–25% within two years of returning to sport. The patterns of ground reaction forces (GRFs) serve as a key biomarker for assessing functional recovery and reinjury risk. Post-ACLR, individuals frequently exhibit abnormal GRFs patterns, including elevated peak vGRF, increased loading rates, and asymmetrical limb loading. These patterns significantly increase the risk of post-traumatic osteoarthritis, affecting over 50% of ACLR patients within 10–15 years. These persistent loading abnormalities are driven by complex biomechanical deficits, influenced by various intrinsic factors. A key intrinsic factor is a pronated foot (PF). Excessive foot pronation, characterized by rearfoot eversion and tibial internal rotation, disrupts the entire lower extremity kinetic chain. This biomechanical misalignment can increase knee valgus and anterior tibial shear forces, thereby increasing rotational and translational stress on the healing graft. Consequently, excessive pronation can sustain abnormal loading patterns long after surgery. During the critical return-to-sport phase, typically between 6 and 9 months post-ACLR, individuals often display a “stiff-legged” gait pattern, marked by reduced knee flexion and increased peak vGRF. These compensatory strategies, initially protective but often persistent, lead to significant limb loading asymmetries, including uneven vGRF and high loading rates, which were observed even 18–24 months post-operative. The persistence of these deficits raises the risk of graft reinjury and accelerates post-traumatic osteoarthritis.