Fatigue as a key factor for testing knee stability with single leg drop landing for injury prevention and return to play tests.

Objectives: Fatigue can decrease knee stability and increase the injury risk. However, fatigue is rarely being applied throughout movement analysis. The aim of this study was to investigate if the knee stability throughout SLDLs differ between cyclic and acyclic sports, before and after fatigue in general, and between the dominant and non-dominant leg of soccer players. Methods: A total of 43 active male (n = 34) and female (n = 9) athletes (age: 26.5 ± 7.2) participated in this study with a pre-post-design. Subjects performed a single leg drop landing (SLDL) from a plyobox. For each leg, the two-dimensional frontal plane projection angle (FPPA) was analyzed. After pretesting the shuttle run test was performed until exhaustion, before repeating the measurements. Results: ANOVA with repeated measures was applied and identified no significance difference for the FPPA between cyclic and acyclic sports (F = 0.98, p = 0.33), a significant difference before and after fatigue (F = 12.49, p = 0.002) and no significant difference between the dominant and non dominant leg of soccer players (F = 4.35, p = 0.26). Discussion: Fatigue seems to be able to have a significant influence on knee stability in the frontal axis. Therefore, fatigue should be included in motion analysis for injury prevention and return to play tests because during this physical state most injuries happen.

Identifying female responders to proximal control exercises in patellofemoral pain syndrome: A clinical prediction rule.

Objectives: Given the high prevalence of patellofemoral pain syndrome (PFPS) and the effectiveness of proximal control exercises, as well as the lack of studies addressing the predictors of this effect, we conducted this study to examine the effects of age, body mass index, symptom duration, and dynamic valgus of the knee on the pain and function responses to proximal control exercises in women with PFPS. Methods: Fifty women with PFPS with a mean age of 25 years, recruited from Ain Shams University, performed proximal control exercises twice weekly for 4 weeks. Knee pain was assessed with the visual analogue scale; knee function was assessed with the Kujala questionnaire; and dynamic knee valgus (DKV) was assessed through Kinovea Computer programmer video analysis. Likelihood ratios were calculated to determine the examination items most predictive of treatment outcomes. Logistic regression analysis identified items in the clinical prediction rule (identification of clinical variables predicting successful outcomes to improve decision-making and treatment efficacy). Results: Proximal control exercises resulted in successful improvement exceeding the minimal clinical important difference (1.8 cm for pain and 8 points for function) in 35 (70%) women with PFPS. Among the four tested predictors, symptom duration (P = 0.032) and DKV (P = 0.007) predicted amelioration of knee pain with proximal control exercises. However, the DKV angle ≥21.5° acceptable area under the curve, sensitivity, and specificity were 0.72, 0.6, and 0.6, respectively (P = 0.015). No predictors of improvement in knee function were identified. Conclusions: Symptom duration and DKV can predict amelioration of PFPS after proximal control exercises.

The effect of videotape augmented feedback on drop jump landing strategy: Implications for anterior cruciate ligament and patellofemoral joint injury prevention.

BACKGROUND: Modification of high-risk movement strategies such as dynamic knee valgus is key to the reduction of anterior cruciate ligament (ACL) and patellofemoral joint (PFJ) injuries. Augmented feedback, which includes video and verbal feedback, could offer a quick, simple and effective alternative to training programs for altering high-risk movement patterns. It is not clear whether feedback can reduce dynamic knee valgus measured using frontal plane projection angle (FPPA). METHODS: Vertical ground reaction force (vGRF), two-dimensional FPPA of the knee, contact time and jump height of 20 recreationally active university students were measured during a drop jump task pre- and post- an augmented feedback intervention. A control group of eight recreationally active university students were also studied at baseline and repeat test. RESULTS: There was a significant reduction in vGRF (p=0.033), FPPA (p<0.001) and jump height (p<0.001) and an increase in contact time (p<0.001) post feedback in the intervention group. No changes were evident in the control group. CONCLUSION: Augmented feedback leads to significant decreases in vGRF, FPPA and contact time which may help to reduce ACL and PFJ injury risk. However, these changes may result in decreased performance. CLINICAL RELEVANCE: Augmented feedback reduces dynamic knee valgus, as measured via FPPA, and forces experienced during the drop jump task and therefore could be used as a tool for helping decrease ACL and PFJ injury risk prior to, or as part of, the implementation of injury prevention training programs.