A muscle strain involves a stretching or tearing of muscle fibers. The most common locations for a muscle strain are your lower back and hamstring, which is the muscle in the back of your thigh. Muscle strains do not cause fever. A fever usually indicates the presence of an infection or illness, according to Harvard Health Publications.
Muscle strains are not at all related to fever and happen when a muscle stretches too far or it contracts too strongly. According to Harvard Health Publications, the risk of a muscle strain is greatest during sports activities, especially contact sports like football, and in sports in which you move from a standing position to a running position very quickly, like basketball or tennis. You can also strain a muscle by lifting a heavy object or slipping on ice.
Symptoms of a muscle strain include pain, swelling and bruising, muscle spasms and a reduced ability to move the strained muscle. You might also experience a pop in the muscle at the time of the injury if the injury completely tore the muscle. The severity of your symptoms depends on the severity of the injury. See a doctor if you have significant pain and can't move the injured area or you have numbness in or anywhere around the injury. Also seek medical care if red streaks are spreading out around the injury or you have a fever -- higher than 100.4 Fahrenheit -- along with significant muscle pain.
When you see the doctor, he will ask you about what you were doing when the muscle pain started and if there was a pop. He will also ask you questions about your fever -- like how many days it has been present. The doctor may also ask about recent weight loss, leg numbness or other symptoms that might indicate a medical problem. To diagnose a strain, he may order X-rays or an MRI. If there is a need, the doctor might order additional tests to check for an infection or illness that may explain muscle pain and fever.
Lower back pain may be associated with a strain, but if your symptoms include fever it could be related to a kidney infection. If you have had a recent urinary tract infection and are now having lower back pain with fever, it is more likely that you have a kidney infection. See your doctor for an evaluation, recommends MayoClinic.com.