The therapeutic effectiveness of inversion traction has only recently come under investigation. The purpose of this study was to use noninvasive methods to determine traction, cardiovascular, and perceived effects of inversion. The Gravity Gym® and Gravity Boot® inversion systems were compared. Treatment order was randomized and 18 normal subjects between the ages of 22 and 31 were suspended in each inversion device for 7 minutes. A computerized method was used for assessing posture. Three-dimensional coordinates were determined for spinous processes C7 through L5 relative to the midpoint of a line drawn between posterior superior iliac spines (S2). Heart rate was palpated and blood pressure was recorded using a standard sphygmomanometer. Pre-, initial, late, and postinversion measurements were taken. Questionnaires administered following each inverted posture assessed levels of discomfort. One-way analysis of variance was conducted to test the significance of results (p < 0.05). Measurements for both systems revealed an increase in L5-S2 distance, a decrease in C7-T12 distance, and a decrease in depth of the thoracolumbar curves. Segments C7-S2, L 1 -S2, L 1 -L2, L3-L4, and L4-L5 were increased in length by the Gravity Gym but not the Gravity Boots. Heart rate decreased and blood pressure increased an average of 20 mm Hg for both systems as subjects were inverted. This pattern was observed throughout the inversion period. Upon return to stand, heart rate increased for both systems while blood pressure decreased only for the Gravity Boot system. Subjects indicated that the Gravity Gym was the more tolerable inversion system.  lnversion can be an effective means of spinal traction but due to elevated blood pressure, inversion may be contraindicated for some patients.

J Orthop Sports Phys Ther 1986;7(5):254-260.

Study Design: Cross-sectional. Objectives: To determine if females with anterior knee pain are more likely to demonstrate hip abduction or external rotation weakness than a similar, asymptomatic, age-matched control group. Background: Diminished hip strength has been implicated as being contributory to lower-extremity malalignment and patellofemoral pain. The identification of reliable and consistent patterns of weakness in this population may help health care professionals establish a more effective treatment plan. Methods and Measures: Hip abduction and external rotation isometric strength measurements were recorded for the injured side of 15 female subjects with patellofemoral joint pain (mean ± SD age, 15.7 ± 2.7 years; age range, 12-21 years). These were compared with strength measurements from the corresponding hip of 15 age-matched female control subjects (mean ± SD age, 15.7 ± 2.7 years; age range, 12-21 years). All strength measurements were made using hand-held dynamometers. Results: Subjects with patellofemoral pain demonstrated 26% less hip abduction strength (P<.001) and 36% less hip external rotation strength (P<.001) than similar age-matched controls. Conclusions: The results indicate that young women with patellofemoral pain are more likely to demonstrate weakness in hip abduction as well as external rotation than age-matched women who are not symptomatic.

J Orthop Sports Phys Ther. 2003;33(11):671-676.
 

Key Words: anterior knee pain, hip abduction, hip external rotation, knee, patella

Study Design: Randomized clinical trial. Objectives: To investigate the clinical efficacy of the addition of the Protonics system to a standard exercise-based patellofemoral rehabilitation protocol. Background: The Protonics system has been suggested as an intervention for patients with patellofemoral pain syndrome (PFPS). However, the effects of this system have not been compared to the effects associated with traditional exercise-based rehabilitation alone. Methods and Measures: Seventeen of 34 females (mean age, 28 years; range, 13-55 years) diagnosed with PFPS were randomly assigned to wear the Protonics system while participating in a conventional exercise-based rehabilitation program. Functional and patient-reported outcome measures were evaluated, including Kujala score and the lateral step-up test. In addition, measurements of hip internal and external rotation, hip extension, and iliotibial band muscle length were compared between groups. Results: Patients in both groups demonstrated improvement in Kujala score (P<.001), performance on the lateral step-up test (P<.001), and pain during the step-up test (P<.001) at the conclusion of the study. However, there was no difference between groups with respect to improvement in Kujala score (P = .33), step-up test performance (P = .47), or pain during the step-up test (P = .24). Patients using the Protonics system demonstrated greater gain in passive hip extension (P = .023) and increased hip external rotation motion (P = .017) at discharge versus patients treated with exercise alone. However, there was no difference in iliotibial band flexibility (P = .80) or hip internal rotation motion (P = .09) between groups. A greater proportion of patients in the Protonics group reported no pain with step-up testing at each 2-week interval. However, the 2.2 fewer visits required by patients in the Protonics group to meet discharge criteria did not achieve statistical significance (P = .08). Conclusions: Patients using the Protonics system demonstrated a shift in available hip rotation and increased passive hip extension flexibility. However, these changes were not outside the bounds of potential measurement error and did not translate into significant functional differences from a similar group treated with exercise alone. The economic implications of an average 2.2-visit decrease in treatment sessions per patient using the Protonics system are uncertain.

J Orthop Sports Phys Ther. 2005;35(4):210-219. doi:10.2519/jospt.2005.1566

Key Words: anterior knee pain, hip rotation, Kujala score, therapeutic exercise