Traumas That Tear Patellar Tendons
Patellar tendon tears most commonly occur due to sudden eccentric contraction of the quadriceps muscle, such as during landing from a jump or during rapid deceleration, but can also result from direct trauma to the anterior knee. 1
Common Traumatic Mechanisms
- Eccentric overload - The most common mechanism involves a sudden eccentric contraction of the quadriceps while the knee is partially flexed, placing excessive tension on the patellar tendon 1
- Direct blunt trauma - A direct blow to the anterior aspect of the knee during sports activities can lead to patellar tendinopathy and eventual rupture 2
- Falls - Particularly falls with the knee in a flexed position that cause sudden quadriceps contraction 3
- Motor vehicle accidents - Significant trauma to the knee during accidents can cause patellar tendon rupture 4
- Acute twisting injuries - Rotational forces applied to the knee while weight-bearing can tear the patellar tendon 4
Risk Factors That Increase Vulnerability to Traumatic Tears
- Pre-existing tendinopathy - Antecedent patellar tendinopathy weakens the tendon structure, making it more susceptible to traumatic rupture 2, 5
- Prior cortisone injections - Local steroid injections can weaken tendon integrity 5
- Systemic conditions - Diabetes, chronic renal failure, hyperparathyroidism increase risk of tendon rupture even with less significant trauma 5
- Medication use - Fluoroquinolone antibiotics and statins can predispose to tendon rupture with minimal trauma 5
- Obesity - Increases mechanical load on the extensor mechanism 5
Clinical Presentation of Traumatic Patellar Tendon Tears
- Palpable defect - Physical examination reveals a gap at the site of tendon rupture 1
- Inability to perform straight leg raise - Complete disruption prevents active knee extension 6
- Patella alta - Superior displacement of the patella visible on radiographs compared to the uninjured knee 6
- Joint effusion - Hemarthrosis is common following traumatic tears 4
Diagnostic Approach for Suspected Traumatic Tears
- Radiographs - Initial imaging should include anteroposterior and lateral views of the knee to assess patellar position and rule out associated fractures 4
- MRI - Most accurate imaging modality for confirming diagnosis and assessing extent of tendon tear 4
- Ultrasound - Can be useful for dynamic assessment but generally less accurate than MRI for partial tears 4
Treatment Considerations
- Complete tears - Require immediate surgical repair to restore extensor mechanism continuity 5, 6
- Surgical techniques - Include transosseous suture repair or suture anchor fixation, with similar biomechanical outcomes 6
- Augmentation - May be necessary in cases with poor tissue quality or chronic tears using autograft, allograft, or synthetic materials 5
- Rehabilitation - Protected weight-bearing in an orthosis with controlled range of motion for approximately 6 weeks 6
Outcomes After Traumatic Patellar Tendon Repair
- Return to sports - Professional athletes can generally return to play following season after repair 1
- Re-rupture rates - Less than 5% when properly treated 5
- Functional outcomes - Most patients regain full range of motion and strength comparable to the uninjured leg 3