What is a hallmark symptom of Grade 3 joint sprains?

A hallmark symptom of Grade 3 joint sprains is severe instability. This indicates a complete tear of the ligament(s) involved, resulting in an inability of the joint to maintain its structural integrity during movement. With a Grade 3 sprain, the joint becomes highly unstable, leading to significant loss of function and increased risk for further injury. This instability is often accompanied by other symptoms such as pain, swelling, and bruising, but the defining characteristic is the significant loss of stability in the joint itself, which profoundly affects range of motion and the capability to bear weight.

The other options do not accurately reflect the characteristics of a Grade 3 sprain. Minimal pain and complete functionality are not typical of this grade, as the severity of the tear usually results in substantial pain and limited function. Likewise, mild swelling would not be expected in a Grade 3 sprain, where significant swelling is more common due to the extent of the injury and associated trauma.