Passive insufficiency occurs when which condition is true?

• A. The length of a muscle prevents full ROM at the joint or joints over which the muscle crosses
• B. A muscle cannot generate force due to fatigue
• C. A joint capsule is too tight
• D. Nerve conduction is slowed

Answer: (A)

Passive insufficiency happens when a muscle that crosses more than one joint isn’t long enough to be stretched across all the joints it crosses, so it prevents full passive range of motion at those joints. In practice, a two-joint muscle like the hamstrings can become taut across both the hip and knee, limiting how far you can move the knee when the hip is positioned to lengthen the muscle. The other options describe different problems—fatigue affecting force, capsular tightness of the joint, or nerve conduction issues—so they don’t explain the restriction caused by the muscle’s insufficient length.