A patient exhibits a weak quadriceps to hamstring strength ratio indicating potential knee instability. Which ratio reflects this condition?

The correct ratio that reflects a weak quadriceps to hamstring strength, indicating potential knee instability, is the 4:1 ratio. This means that an imbalance exists, where the strength of the quadriceps is significantly greater than the strength of the hamstrings.

In healthy individuals, a more balanced ratio is often expected, typically around 2:1 favoring the quadriceps. When this ratio is excessively high (like 4:1 or more), it suggests that the quadriceps are disproportionately stronger compared to the hamstrings, which can lead to knee instability. The hamstrings play a crucial role in stabilizing the knee during activities involving knee flexion and extension.

In this context, a 6:1 or a 3:1 ratio would further indicate an imbalance, but these values suggest even greater weakness in the hamstring muscle group. A 2:1 ratio is generally considered a standard for normal function, not an indication of instability. Therefore, the presence of a weak quadriceps to hamstring strength ratio that leads to knee instability is best represented by a ratio significantly above normal, like the 4:1 ratio.