Question
A 32 year old basketball player lands awkwardly and feels a pop below his kneecap. He cannot extend the knee against gravity.
- Describe the radiograph and the measurement that helps.
- What risk factors predispose to this injury?
- Outline the repair and rehabilitation.
Answer
Radiograph
- High riding patella (patella alta)
- Insall-Salvati ratio over 1.2 suggests patellar tendon rupture
- Look for an inferior pole avulsion fragment
- Ultrasound or MRI confirms the level of rupture
Risk factors
- Under 40, patellar tendinopathy and jumping sports
- Systemic lupus, rheumatoid arthritis, diabetes and chronic renal failure
- Corticosteroid injection and fluoroquinolones
- Previous TKA or tendon harvest
- Bilateral rupture should prompt systemic workup
Repair
- Early repair within 2 weeks gives better results
- Transosseous patellar tunnels or suture anchors with locking sutures
- Repair the medial and lateral retinacula
- Protect with a cerclage wire or tape augmentation
- Check patellar height against the other side
- Chronic ruptures need V-Y quadriceps lengthening and hamstring or allograft reconstruction
Rehabilitation
- Brace in extension, weight bear as tolerated
- Progressive flexion over 6 weeks
- Return to sport at 6 months
Related pages
Author Contributions
Orthofracs team
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.