What are the three basic elements of rating for knee disability?

• A. Adduction, abduction and calf atrophy
• B. Adduction, abduction and thigh atrophy
• C. Limitation of flexion and extension, instability and thigh atrophy
• D. Limitation of flexion and extension, instability and calf atrophy

Answer: (C)

Knee disability rating rests on three core factors: how much the knee can bend and straighten (range of motion), how the knee holds up under stress (stability), and the condition of the thigh muscles surrounding the knee. Limitation of flexion and extension reflects reduced bending and straightening, which directly affects daily activities like walking and climbing stairs. Instability indicates ligamentous laxity or giving way, showing the knee’s reliability under load. Thigh atrophy signals loss of muscle mass around the knee, which compromises support and control of the joint.

The option that lists these three elements—limitation of flexion and extension, instability, and thigh atrophy—best fits how knee disability is evaluated. Choices that include adduction/abduction or calf atrophy introduce factors not used as the three basic rating elements.