Patellofemoral Joint Loading During Bodyweight One-Legged and Two-Legged BOSU and Floor Squats.

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° between 10°-100° 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°, 50°, and 70° knee-angles during squat descent and 60° and 50° 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°, 40°, 50°, 60°, and 100° knee-angles during squat-descent, and 100°, 90°, 80°, and 70° 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° - 50°); 2) two-legged floor squats at lower knee angles (0° - 50°); 3) one-legged BOSU and floor squats at lower knee angles (0° - 50°); 4) two-legged BOSU squats at lower and higher knee angles (0° - 100°); 5) two-legged floor squats at lower and higher knee angles (0° - 100°); 6) one-legged BOSU and floor squats at lower and higher knee angles (0° - 100°).

Level of evidence: 2.