Final answer:
If the knees cave in (knee valgus) during a Single-leg Squat Assessment, it indicates that the gluteus medius and the vastus medialis oblique (VMO) muscles are underactive. Strengthening the underactive muscles can help improve knee alignment and stability.
Step-by-step explanation:
If the knees cave in (knee valgus) during a Single-leg Squat Assessment, it indicates that certain muscles are underactive. Specifically, the muscles that are likely underactive are the gluteus medius and the vastus medialis oblique (VMO). These muscles play important roles in stabilizing the knee and preventing it from caving inwards.
When the gluteus medius is underactive, it fails to properly control the position of the knee during the squat, leading to knee valgus. Similarly, when the VMO is underactive, it is unable to fulfill its role in stabilizing the patella and preventing the knees from collapsing inwards.
In order to address knee valgus, it is crucial to strengthen the underactive muscles, particularly the gluteus medius and VMO. Exercises such as side-lying leg lifts and single-leg squats with proper form can help activate and strengthen these muscles, improving knee alignment and stability.