Because muscles are soft tissues, they do not appear on X-rays. So muscle testing is an important part of the physical examination. Weakness in a muscle may indicate injury to the tendons that connect the muscle to bone, injury to the nerves that enervate the muscle, or a generalized weakness of the muscle itself from disuse.
To test the strength of your muscles, your physician may ask you to move in certain ways while he or she applies a resistive force. For example, your physician may ask you to sit in a chair and then attempt to raise one knee as the doctor presses down on your upper leg. Or, your physician may hold your elbow at a 90-degree angle and ask you to bend your wrist down. Measuring grip strength by asking you to squeeze the doctor's hand is another type of muscle test.