Consequence of Functioning at the End Range of Joint Motion: Implications on Anterior Knee Pain

“Excessive” and/or “delayed” subtalar joint (STJ) pronation has been linked to overuse injuries because of its influence on tibial internal rotation (TIR). The transfer of STJ pronation to TIR occurs via the talocrual joint, believed to have limited transverse plane motion. However, studies have shown the talocrural joint to have more transverse plane motion than once believed, therefore it is feasible that the STJ will only influence the motion of the tibia once this motion has been exhausted. Currently, studies evaluating this relationship have focused on peak joint angles and excursion without reference to the amount of motion available at the ankle joint complex (AJC). Therefore the purpose of these studies were to evaluate whether runners with anterior knee pain (AKP) utilize a greater percentage of their available eversion motion (eversion buffer), evaluate the effects of small eversion buffers on coordination, and evaluate the influence of orthotics on those with AKP and with the smallest eversion buffers. This study found healthy and injured runners, for the most part, presented with no significant differences in traditional pronation related variables. The one exception was peak pronation velocity, where injured runners demonstrated faster velocities. On the other hand injured runners had significantly smaller eversion buffers which lead them to change their coordinative pattern earlier during stance. This difference in pattern also caused the intra-individual coupling variability to peak earlier during stance. Orthotics successfully controlled the kinematics of the AJC and increased the eversion buffer of injured runners and in those displaying the smallest buffers. While orthotics successfully influenced the kinematics of the AJC, they did not influence those of the tibia and knee. These changes at the AJC did not have a strong impact on the coordinative patterns of the lower extremity, however demonstrated a trend toward being able to influence the intra-individual coupling variability. In summary, injured runners demonstrated smaller eversion buffers and changed their coordinative pattern earlier during stance. While orthotics successfully increased the eversion buffer, they did not strongly influence coordination variables. Future studies analyzing pronation related variables in injured populations should evaluate them relative to the available motion at the AJC