Flesh pain on one side of the waist may be caused by lumbar muscle strain, muscle sprain, lumbar intervertebral disc herniation and so on. 1. Lumbar muscle strain: it is a chronic injurious inflammation of the lumbar muscles and their attachment points of fascia or periosteum, which is one of the common causes of lumbar pain, and the main symptom is lumbar or lumbosacral distension, soreness and pain, recurring, which may lead to the patient to have a lumbar muscle pain on one side. 2. Muscle sprain: due to excessive pulling of muscles and ligaments, causing injury or tearing, which may lead to muscle pain on one side of the patient’s waist. 3. Herniated lumbar discs: Herniated discs can irritate the nerve roots, affecting the lumbar region and lower limbs, causing soreness and pain in the innervated area, leading to symptoms of lumbar side pain. There may be other causes of lumbar pain, so it is recommended that the patient consult a doctor in a timely manner to clarify the cause of the disease and follow the doctor’s instructions for standardized treatment.