If a female patient has sudden lumbar pain and is unable to straighten her back, it may be due to the following reasons: 1. This condition may be caused by an acute lumbar sprain. Some female patients have poor lumbar strength and may experience a strain on their lumbar muscles when lifting heavy objects or bending over. The patient will experience severe pain in the lower back and will only be able to maintain a bent posture, once the upper body is forced to straighten up, it will induce more pronounced pain. 2. This condition may be caused by fractures in the lower back, some female patients may have osteoporosis due to malnutrition, or excessive age. Such patients are prone to pathological fractures of the lumbar spine during activity, and the above symptoms may occur. 3. This condition is also common in female patients with urinary stones. Some female patients may have kidney stones due to prolonged low water intake, and this lesion can cause severe colic, causing the patient to experience the above symptoms.