Synopsis
Differentiate patellar fracture from quadriceps and patellar tendon rupture, test active extension correctly, identify open or articular injury, and choose protection, early motion or surgical repair according to extensor continuity and congruity.
- Inspect anterior skin and wounds, palpate patella, quadriceps and patellar tendon and compare patellar height with the opposite knee.
- Test active straight-leg raise with the hip flexed slightly and knee supported; repeat after adequate analgesia when pain or haemarthrosis limits effort.
- Document distal pulses, peroneal and tibial nerve function and knee-dislocation signs because vascular injury is more urgent than extensor classification.
- Obtain AP and lateral knee radiographs and a skyline view only when safe; look for displacement, articular step, patellar height and osteochondral fragments.
- Use ultrasound or MRI when tendon continuity remains uncertain; CT helps define complex comminuted or articular fracture for surgery.
- An undisplaced or minimally displaced fracture with intact active extension can often use a brace locked in extension, weight bearing as instructed and early specialist-guided motion.
- Disrupted extensor mechanism, open fracture, significant articular incongruity or unstable displacement usually requires operative fixation or tendon repair.
- Monitor skin, wound, extension lag, flexion and quadriceps function and prevent VTE according to immobilisation and patient risk.
Key red flags
Absent distal pulses, cool foot, expanding popliteal swelling or new peroneal and tibial deficit after knee trauma requires immediate vascular and orthopaedic action.
An anterior wound, exposed tendon or bone, haemarthrosis under tense skin or a palpable gap with lost active extension needs urgent surgical assessment.
Inability to perform a straight-leg raise after adequate analgesia suggests extensor disruption, but apparent ability can persist through intact retinacula and does not exclude a displaced fracture.
Investigation priorities
Define patellar fracture, displacement and patellar height.
Management branches
Anterior knee trauma causes haemarthrosis, deformity or extension weakness.
- Perform trauma and distal neurovascular assessment, inspect wounds and support the knee in a comfortable extended position.
- Give analgesia, palpate the full extensor chain and test straight-leg raise, repeating after pain treatment when necessary.
- Cover any open wound, give immediate network intravenous prophylaxis and obtain urgent orthopaedic review without bedside probing.
- Obtain adequate radiographs and use tendon or cross-sectional imaging when the functional and bony findings disagree.
Active extension is intact and fracture displacement and articular congruity are acceptable.
- Fit an extension brace or splint and set explicit weight-bearing, skin and range-of-motion instructions.
- Arrange fracture-clinic review and repeat radiographs when initial stability or later displacement is a concern.
- Begin graded knee flexion and quadriceps activation under specialist guidance while protecting the healing fracture.
- Review VTE risk and provide prophylaxis when immobilisation and patient factors outweigh bleeding risk.