Anterior-posterior knee laxity increased by exercise: Quantitative evaluation of physiologic changes

Context: The high incidence of lower limb injuries associated with physical exercises in military conscripts suggests that fatigue may be a risk factor for injuries. Researchers have hypothesized that lower limb injuries may be related to altered ankle and knee joint position sense (JPS) due to fatigue.Objective: To evaluate if military exercises could alter JPS and to examine the possible relation of JPS to future lower extremity injuries in military service.Design: Cohort study. Setting: Laboratory. Patients or Other Participants: A total of 50 male conscripts (age ¼ 21.4 6 2.3 years, height ¼ 174.5 6 6.4 cm, mass ¼ 73.1 6 6.3 kg) from a unique military base were recruited randomly.Main Outcome Measure(s): Participants performed 8 weeks of physical activities at the beginning of a military course. In the first part of the study, we instructed participants to recognize predetermined positions before and after military exercises so we could examine the effects of military exercise on JPS. The averages of the absolute error and the variable error of 3 trials were recorded. We collected data on the frequency of lower extremity injuries over 8 weeks. Next, the participants were divided into 2 groups: injured and uninjured. Separate 2 3 2 3 2 (group-by-time-by-joint) mixed-model analyses of variance were used to determine main effects and interactions of these factors for each JPS measure. In the second part of the study, we examined whether the effects of fatigue on JPS were related to the development of injury during an 8-week training program. We calculated Hedges effect sizes for JPS changes postexercise in each group and compared change scores between groups.Results: We found group-by-time interactions for all JPS variables (F range ¼ 2.86-4.05, P , .01). All participants showed increases in JPS errors postexercise (P , .01), but the injured group had greater changes for all the variables (P , .01).Conclusions: Military conscripts who sustained lower extremity injuries during an 8-week military exercise program had greater loss of JPS acuity than conscripts who did not sustain injuries. The changes in JPS found after 1 bout of exercise may have predictive ability for future musculoskeletal injuries.Key Words: fatigue, proprioception, lower extremity, muscles Key PointsAfter an 8-week military exercise program, the loss of joint position sense (JPS) acuity was greater in injured than in uninjured conscripts. The JPS changes were greater in the ankle than in the knee joint. Greater JPS changes postexercise might increase the risk of subsequent musculoskeletal injury during basic training.

Section: Discussionmentioning

confidence: 99%

Military Exercises, Knee and Ankle Joint Position Sense, and Injury in Male Conscripts: A Pilot Study

Mohammadi

Azma

Naseh

et al. 2013

“…To control for the effects of exercise, all participants refrained from activity on the day that knee joint laxity values were obtained. 46,47 Anterior knee laxity was defined as the anterior displacement (in millimeters) of the tibia relative to the femur when a 133-N anteriordirected load was applied to the posterior aspect of the tibia (KT-2000 Knee Arthrometer; MEDmetric Corporation, San Diego, CA). Genu recurvatum was defined as the amount of knee hyperextension (in degrees) when the participant maximally extended the knee with the distal thigh supported by a 4-in (10-cm) bolster.…”

Section: Laxity Measuresmentioning

confidence: 99%

Identifying Multiplanar Knee Laxity Profiles and Associated Physical Characteristics

Shultz

Dudley

Kong

2012

Context: A single measure of knee laxity (ie, measurement of laxity in a single plane of motion) is probably inadequate to fully describe how knee joint laxity is associated with anterior cruciate ligament injury.Objective: To characterize interparticipant differences in the absolute and relative magnitudes of multiplanar knee laxity (ie, sagittal, frontal, and transverse planes) and examine physical characteristics that may contribute to these differences.Design: Descriptive laboratory study. Setting: University research laboratory. Patients or Other Participants: 140 participants (90 women, 50 men).Main Outcome Measure(s): Using cluster analysis, we grouped participants into distinct multiplanar knee laxity profiles based on the absolute and relative magnitudes of their anterior knee laxity (AKL), genu recurvatum (GR), and varusvalgus (VV) and internal-external rotation (IER) knee laxity. Using multinomial logistic regression, we then examined associations between the different laxity profile clusters and physical characteristics of sex, age, activity level, general joint laxity, body mass index, thigh strength, and 8 measures of lower extremity anatomical alignment.Results: Six clusters were identified: low (LOW), moderate (MOD) and high (HIGH) laxity overall and disproportionally higher VV/IER (MOD VV/IER ), GR (HIGH GR ), and AKL (HIGH AKL ) laxity. Once all other physical characteristics were accounted for, the LOW cluster was more likely to be older, with longer femur length. Clusters with greater magnitudes of VV and IER laxity were more likely to be younger and to have lower body mass index, smaller Q-angle, and shorter femur length (MOD, HIGH, MOD VV/IER ) and less thigh strength (HIGH). The HIGH GR cluster was more likely to be female and to have a smaller tibiofemoral angle and longer femur length. The HIGH AKL cluster was more likely to have greater hip anteversion and navicular drop.Conclusions: The absolute and relative magnitudes of a person's multiplanar knee laxity are not always uniform across planes of motion and can be influenced by age, body composition, thigh strength, and structural alignment. Except in HIGH GR , sex was not a significant predictor of cluster membership once other physical characteristics were taken into account.

“…Knee-joint laxity can increase by as much as 20% above initial preexercise (baseline) values within 20 to 30 minutes of starting intermittent sport-related activity [12][13][14] and can continue to rise with increasing exercise duration. 12,15 These increases coincide with the time in games when injury rates begin to rise.…”

mentioning

confidence: 99%

Changes in Fatigue, Multiplanar Knee Laxity, and Landing Biomechanics During Intermittent Exercise

Shultz

Schmitz

Cone³

et al. 2015