<s>[INST] I have hip pain that came on suddenly and would alternate between very painful and no pain at all. It go better after a few days and seems to have gone away. Wondering about exercise, I usually work out hard about 3 times a week. I wonder too what caused it and what might prevent it. [/INST] Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Sudden onset hip pain can be from a strain or tear from an acute episode. Acute hip pain can also be from bruises from direct impact. Sharp pain in the hip can be sudden and can be referred from the lumbar spine. Sudden hip pain can be from femoral fractures or a more severe hip dislocation. May be a vascular necrosis, infection,  rectus femoris tendinitis, labial tear ,hip sprain,rectus femoris avulsion etc. Hope I have answered your query. Let me know if I can assist you further. </s>