Which muscle isometrically stabilizes the lumbo-pelvic-hip complex (LPHC) and knee?

The muscle that isometrically stabilizes the lumbo-pelvic-hip complex (LPHC) and knee is the gluteus maximus. This muscle plays a significant role in maintaining stability within the LPHC during various movements and postures.

When the gluteus maximus contracts isometrically, it helps to support the pelvis and lower back, creating a stable base for movements that involve the legs and hips. This stabilization is crucial during activities such as standing, walking, and any other functional movements that require balance and control. The gluteus maximus also assists in hip extension, which is important for propelling the body forward during walking or running.

In contrast, while the sartorius, rectus femoris, and psoas major have their functions, they do not primarily serve the same stabilizing role for the LPHC and knee. The sartorius is involved in flexing the hip and knee but does not provide significant stabilization. The rectus femoris, part of the quadriceps group, primarily extends the knee, and while it crosses the hip, its stabilization role is not as prominent. The psoas major is primarily a hip flexor and does not focus on stabilization of the LPH