Tendonitis, or tendinitis, happens when a tendon either swells or sustains tiny tears. Tendonitis usually develops over time. For some people, however, it is a sudden injury. It is possible for tendonitis to get better with home treatment and gentle exercise, especially when people begin treatment early.
Hamstring tendonitis is an injury to one or both of the hamstring tendons, which are part of the thick band of muscles and tendons called the hamstrings. The hamstring tendons connect the hamstring muscles to the pelvis, knee, and shinbones.
As the hamstrings help the knee bend, an injury to either the tendons or the muscles can cause knee pain and difficulty walking or bending the knee. People often develop tendonitis because of overuse.