Low back pain 3 months after femoral head replacement is mainly considered degenerative lesions such as osteophytes, lumbar disc herniation and lumbar muscle strain. 1. Degenerative lesions such as osteophytes: Lumbar pain may be caused by lumbar spine osteophytes, and symptoms such as numbness of the lower limbs may occur when the proliferated bone compresses the related nerve tissues. 2. Lumbar disc herniation: you need to consider whether the lumbar pain is caused by lumbar disc herniation, which is a typical symptom of lumbar localized pain and activity limitation. 3. Lumbar muscle strain: After femoral head replacement surgery, you often need to stay in bed for a long time, which may cause lumbar muscle strain due to inappropriate lying or sitting posture, and then you will feel lumbar pain. It is recommended to consult a doctor for lumbar pain in a timely manner. Under the guidance of the doctor, relevant examinations such as lumbar MRI should be performed to clarify the cause of the pain and to make appropriate diagnosis and treatment.