Abstract
<p>Background While one-legged and two-legged bodyweight squats on unstable and stable surfaces are commonly used during patellofemoral rehabilitation, patellofemoral loading during these exercises is unknown. Understanding how patellofemoral force and stress magnitudes affects different squat variations will aid clinicians in determining how and when to prescribe and progress these squatting types of exercises in patients with patellofemoral pain. Hypothesis/Purpose To quantify patellofemoral force and stress between two squat type variations (BOSU squat versus floor squat) and between two leg variations (one-legged squat versus two-legged squat). It was hypothesized that patellofemoral force and stress would be greater in BOSU squat than floor-squat, and greater in one-legged squat than two-legged squat. Study Design Controlled laboratory biomechanical, repeated-measures, counterbalanced design. Methods Sixteen healthy participants performed one-legged and two-legged BOSU and floor squats. Kinematic and ground-reaction force data were used to calculate resultant knee force and torque using inverse-dynamics, with electromyographic data employed in a knee muscle model to predict resultant knee force and torque at every 10 degrees between 10 degrees-100 degrees knee-angles during the squat-descent and squat-ascent. Repeated-measures 2-way ANOVA (p < 0.01) was employed for statistical analyses. Results Collapsed across one-legged and two-legged conditions, patellofemoral joint force and stress were significantly greater during floor squats than BOSU squats at 40 degrees, 50 degrees, and 70 degrees knee-angles during squat descent and 60 degrees and 50 degrees knee-angles during squat ascent. Collapsed across BOSU and floor squats, patellofemoral joint force and stress were significantly greater for one-legged squats than two-legged squats at all knee-angles. Significant interactions between squat types and leg conditions were found at 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 100 degrees knee-angles during squat-descent, and 100 degrees, 90 degrees, 80 degrees, and 70 degrees knee-angles during squat-ascent, with patellofemoral joint force and stress significantly greater in two-legged floor-squat than two-legged BOSU squat, but no significant differences between one-legged floor-squat and one-legged BOSU squat. Conclusions Squatting progression employing lower to higher patellofemoral loading over time during PFP rehabilitation may be considered: 1) two-legged BOSU squats at lower knee angles (0 degrees- 50 degrees); 2) two-legged floor squats at lower knee angles (0 degrees- 50 degrees); 3) one-legged BOSU and floor squats at lower knee angles (0 degrees- 50 degrees); 4) two-legged BOSU squats at lower and higher knee angles (0 degrees- 100 degrees); 5) two-legged floor squats at lower and higher knee angles (0 degrees- 100 degrees); 6) one-legged BOSU and floor squats at lower and higher knee angles (0 degrees- 100 degrees). Level of Evidence 2</p>