Analysis of Lower Extremity Joint Moment and Power during Squat in Female Patients with Genu Varum

Abstract

Genu varum is a condition where the center of the knee joint is bent outward on a straight line that connects from the centers of the hip joint to that of the knee joint like an archerˈs bow (Mansfield & Neumann, 2009). Genu varum is divided into different levels, depending on the size of the gap measured when a person stands with the legs closed; Level I is diagnosed when the gap is <2.5 cm, while Level 2 is between 2.5 and 5.0 cm, Level 3 between 5.0 and 7.5 cm, and Level 4 >7.5 cm (Yang, 2013). Genu varum causes fatigue and deformity by increasing the instability of the lower extremity, which overloads the hip, knee, and ankle joints and accelerates the decline of body functions and degeneration of the joints (Wegener, Kisner, & Nichols, 1997). As a result, the vastus medialis and gluteus medius in the quadriceps, hamstring, and tibialis anterior grow weak, while the lower extremity loses its normal function as the tensor fasciae latae and soleus become short, making the joints swollen and causing pain (Cook, Burton, Kiesel, Rose, & Bryant, 2010). In addition, it also affects walking abilities as the patella is not in the normal position (Fry, Smith, & Schilling, 2003). There have been a few exercise programs developed to correct genu varum; stretching, band exercise, sling exercise, and muscle resistive exercise have been reported to correct genu varum (Jacobon & Speechley, 1990; Smith, 1994). Clinically, there has been much effort to correct genu varum by combining various exercises together, and in particular, much attention is being paid to strengthening of the quadriceps and hamstring that contribute to the stability of the knee joint (Wayne & Susan, 2001). Squat exercise is a multi-joint exercise that is the most well-known to strengthen the quadriceps and hamstring while flexing the hip, knee, and ankle joints simultaneously and developing the muscles of the lower extremity needed to correct genu varum (Palmitier & Scott, 1991). There are three types of squat exercise according to squat depth, including quarter squat, half squat, and full squat, and according to the knee angle, it can be further divided into semi squatting (40°), half squatting (70~100°), and deep squatting (≥100°) (Escamilla, 2001). Squat exercise is good in training the muscles of the lower extremity; therefore, a correct position is required. With a wrong squatting position, the lower back and the knee can get injured (Fry, 1993; OˈShea, 1985; Williams, 1980); hence, a correct position to prevent this should be taught in performing the exercise. Squat exercise is the most representative exercise that strengthens the muscles of the lower extremity and develops the muscles needed to correct genu varum. As such, it is essential for women with genu varum to perform such exercise to not only correct genu varum but also develop the needed muscles. However, most of the previous studies where the squat exercise was the variable focused on people without genu varum or athletes, while there have been almost no objective data or research conducted on women with genu varum. Therefore, the preKorean Journal of Sport Biomechanics 2016; 26(4): 407-412 http://dx.doi.org/10.5103/KJSB.2016.26.4.407 http://e-kjsb.org eISSN 2093-9752 ORIGINAL