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Yumeng Li, Jupil Ko, Marika A. Walker, Cathleen N. Brown, and Kathy J. Simpson

The purpose of the present study was to examine the effect of chronic ankle instability (CAI) on lower-extremity joint coordination and stiffness during landing. A total of 21 female participants with CAI and 21 pair-matched healthy controls participated in the study. Lower-extremity joint kinematics were collected using a 7-camera motion capture system, and ground reaction forces were collected using 2 force plates during drop landings. Coupling angles were computed based on the vector coding method to assess joint coordination. Coupling angles were compared between the CAI and control groups using circular Watson–Williams tests. Joint stiffness was compared between the groups using independent t tests. Participants with CAI exhibited strategies involving altered joint coordination including a knee flexion dominant pattern during 30% and 70% of their landing phase and a more in-phase motion pattern between the knee and hip joints during 30% and 40% and 90% and 100% of the landing phase. In addition, increased ankle inversion and knee flexion stiffness were observed in the CAI group. These altered joint coordination and stiffness could be considered as a protective strategy utilized to effectively absorb energy, stabilize the body and ankle, and prevent excessive ankle inversion. However, this strategy could result in greater mechanical demands on the knee joint.

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Jupil Ko, Erik Wikstrom, Yumeng Li, Michelle Weber, and Cathleen N. Brown

Context: The modified Star Excursion Balance Test (mSEBT) and Y-Balance Test (YBT) are common dynamic postural stability assessments for individuals with chronic ankle instability (CAI). However, the reach distance measurement technique and movement strategy used during the mSEBT and YBT differ. To date, no studies have compared task performance differences on these tests in CAI patients. Objective: To determine whether individuals with CAI perform the mSEBT and YBT differently. Design: Cross-sectional. Setting: Biomechanics laboratory. Participants: Of 97 consented participants, 86 (43 females, 43 males; age 21.5 [3.3] y, height 169.8 [10.3] cm, mass 69.5 [13.4] kg), who reported ≤25 on the Cumberland Ankle Instability Tool, ≥11 on the Identification of Functional Ankle Instability, and had a history of a moderate to severe ankle sprain(s) participated. Interventions: Participants were instructed to perform the mSEBT and YBT in a predetermined counterbalanced order. Three anterior, posteromedial, and posterolateral trials of each test were completed on the involved limb after 4 practice trials. Test direction order was randomized for each participant. Main Outcome Measures: Normalized (expressed in percentage) reach distance in each direction. Paired sample t tests were performed to compare each of the 3 directions between the mSEBT and YBT. Results: Significantly shorter reach distances in the anterior (58.9% [5.8%] vs 61.4% [5.4%], P = .001) and the posteromedial (98.8% [8.6%] vs 100.8% [8.1%], P = .003) directions were noted on the mSEBT relative to the YBT. No differences in the posterolateral directions were observed. Conclusions: Within those with CAI, mSEBT and YBT normalized reach distances differ in the anterior and posteriomedial directions. As a result, clinicians and researchers should not directly compare the results of these tests.

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Adam B. Rosen, Jupil Ko, Kathy J. Simpson, and Cathleen N. Brown

Patellar tendinopathy is often managed with a patellar tendon strap, however, their effectiveness is unsubstantiated. The purpose of this study was to determine if straps altered pain or lower extremity kinetics of individuals with patellar tendinopathy during landing. Thirty participants with patellar tendinopathy and 30 controls completed drop jumps with and without patellar tendon straps. Wearing the strap, tendinopathy participants demonstrated significantly decreased pain and reduced knee adductor moment; all participants displayed significantly decreased anterior ground reaction force while wearing a strap. Patellar tendon strapping may reduce pain due to alterations in direction and magnitude of loading.