Pain in the hip from swimming is often related to the following causes: 1. It may be caused by a muscle or tendon strain that has developed here. This condition is most common when patients swim breaststroke. This may be caused by a strain on the muscles and tendons in the hip joint during vigorous flexion and extension, resulting in hip pain. 2. It may be caused by sterile inflammation in the hip. For example, if the patient sits on a cold stone surface after swimming, it may cause inflammation of the bursa of the sciatic tuberosity, which may lead to pain here. 3. It may be caused by nerve-related lesions. For example, if the patient has previous neuropathy like sciatica during swimming, the stimulation of cold water may lead to the recurrence of such neuropathy, which may result in radiated pain in the buttocks and lower limbs. 4. It may also be caused by muscle fatigue in the buttocks. In the process of swimming, due to overexcitement, patients may do intense activities, which may lead to a large amount of lactic acid deposition inside the muscles of the buttocks, thus producing pain in the buttocks.