Doctor, I have a problem where muscles anywhere in my body can suddenly cramp, pull, or twist on their own. When this happens, I lose control over the affected muscle, and it causes very severe pain. It most commonly affects my stomach, neck, mouth, and lower limbs. I also experience muscle pulling in my lower limbs. After yawning, my jaw sometimes locks (locking of the temporomandibular joint/TMJ), making it difficult to close or move my mouth normally. This condition appears to run in my family. My father also has the same problem. I would like to know what could be causing it and whether I need any investigations or treatment.