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Saturday, March 18, 2000

Knee alignment may cause more female injuries

Subtle change in knee alignment can influence knee and ankle joint forces, moments and muscle activation characteristics. Researchers who conducted a study presented poster exhibit 294 observe that athletic females present valgus knee alignment more often than males and more commonly sustain non-contact related ACL and patellofemoral pathology. Their study indicates that a lack of an anterior mean plantar force location shift by females with valgus knee alignment suggests decreased use of ankle and subtalar joint muscular synergists for dynamic knee stabilization.

The researchers believe this finding may partially explain the increased frequency of non-contact related knee injuries among this group. Females with this alignment may particularly benefit from knee injury prevention programs which train coordinated ankle, subtalar and knee joint muscle functions.

The study assessed the relationship between frontal plane knee alignment and gender to mean plantar force location during a single leg stance dynamic postural stability challenge. Associated variables such as standing foot angle, foot length, height and weight also were assessed. Fifty-six non-impaired adolescent athletes (29 female, 27 male) served as test subjects. Female and male subject weight was 57.9 + 11 kg and 75.5 + 15 kg, respectively. Female and male subject height was 166.8 + 4 cm and 178.4 + 6 cm, respectively.

The left lower extremity of all subjects was assessed for frontal plane knee alignment, standing foot angle and foot length, using anatomically relevant markers, a grided mat and 2-D videographic techniques (30 Hz). Dynamic postural stability was assessed using instrumented insole plantar force sensors (25 Hz) during vision-denied left, lower extremity stance on a 3.8 cm-thick foam surface. Subjects attempted to maintain 20-degree knee flexion during testing. Subjects were grouped for statistical analysis based upon frontal plane knee alignment (group 1 = varus or valgus < 5 degree; group 2 = varus alignment of > 5 degree; and group 3 = valgus alignment of > 5 degree). Mean plantar force locations were calculated following data collection. A series of two-way ANOVA (group, gender) and Tukey HSD post-hoc tests delineated statistical significance (p <.05).

Although males were taller, weighed more and had longer foot length than females, these variables did not differ between groups. Males with valgus knee alignment had a more anterior mean plantar force location (forefoot-directed) during single leg stance than males with neutral knee alignment (mean difference = 5.2 mm, p = 0.036). Females with similar alignments did not present this relationship suggesting greater dependence upon non-contractile, passive methods of postural stability.

Co-authors of the study, all from the University of Kentucky, Lexington, Ken., are Steve Smith, BS; Thomas Armsey, MD, assistant professor family practice, primary care sports medicine; Darren L. Johnson, MD, chief, section of sports medicine, associate professor orthopaedic surgery; and John A. Nyland, MD, associate professor, School of Physical Therapy-College of Medicine.

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Last modified 06/March/2000 by IS