What common sign might indicate a patellar tendon tear?

A patellar tendon tear often results in the inability to extend the knee due to the disruption of the tendon itself. The patellar tendon plays a crucial role in the extension of the leg; it connects the kneecap (patella) to the shinbone (tibia) and is integral to the quadriceps muscle functionality. When this tendon is torn, the muscular action necessary for extending the knee is compromised.

The individual may find it impossible to actively straighten their leg, which is a key indicator of the injury. This inability can be accompanied by other symptoms, but specifically highlights the functional loss associated with a complete or significant tear. Other signs, such as severe pain, a popping sensation, or difficulty jumping, may be present but do not specifically denote the mechanical dysfunction as directly as the inability to extend the knee does.