Yes, a tendon infection can spread if left untreated or if the infection is not effectively controlled. In cases of tenosynovitis, where the infection affects the synovial sheath surrounding the tendon, there is a risk of the infection spreading to nearby tissues, joints, or even into the bloodstream. This can lead to more severe complications, such as septicemia or systemic infection. Prompt medical attention, proper antibiotic treatment, and surgical intervention, if necessary, are crucial to prevent the spread of the infection and minimize the risk of complications. Regular monitoring and follow-up care are important to ensure the infection is effectively treated and to prevent further spread.