What causes spondylolysis?

Repeated spinal extension and rotation can load this area faster than it adapts, particularly during growth or demanding sport. A single major injury is a less common route, and individual bone anatomy may influence susceptibility.

The affected bridge is called the pars interarticularis. Repetitive stress can first provoke a bone reaction and may progress to a small crack. The defect can be present on one or both sides of a vertebra.

Some people have no symptoms. When symptoms occur, spondylolysis commonly presents with lower-back pain that worsens with extension, impact or prolonged activity. Tight hamstrings and altered movement may accompany it. Diagnosis depends on the history, examination and, when appropriate, imaging rather than symptoms alone.

Temporarily reduce movements that reproduce back pain, especially repeated arching, twisting and impact. Complete inactivity is not always needed; comfortable daily movement can usually continue within clinical guidance.

Physiotherapy may build trunk and hip strength, improve movement control and plan a staged return to training. The programme should reflect symptoms, examination findings, skeletal maturity and sporting demands. Bracing or specialist review may be considered in selected cases.

Arrange assessment for persistent activity-related back pain, pain that repeatedly returns with sport, or discomfort that limits walking, sleep or normal tasks. Early review is especially useful for a growing athlete whose pain is triggered by back extension.

Seek urgent medical care for new leg weakness, numbness around the groin, loss of bladder or bowel control, fever with significant back pain, or pain after major trauma. These warning signs require evaluation for problems beyond an uncomplicated pars stress injury.

Ask whether imaging is needed, which movements should be modified, and how progress will be judged. Clarify the strength and movement targets for returning to sport, whether technique or training volume contributed, and what symptoms should prompt another review.