Patella Fracture
Classification systems
- AO/OTA grouping for the patella
- Displaced versus undisplaced with extensor mechanism intact or disrupted
Mechanism
A direct blow to the front of the knee, as in a fall onto the flexed knee or a dashboard impact, tends to comminute the patella. An indirect violent eccentric quadriceps contraction against a flexing knee produces a transverse fracture with separation. Assessment always centres on whether the extensor mechanism is intact.
Age considerations
- Paediatric
- The sleeve fracture is the pattern to know: a cartilaginous sleeve avulses from the pole with only a small bony fleck visible, so the radiograph understates the injury. Patella alta or baja on the lateral view and an inability to extend are the clues.
- Young adult
- Direct high-energy patterns with comminution; anatomical restoration of the articular surface and a construct that tolerates early motion are the aims, because stiffness and extensor weakness are the functional penalties.
- Elderly
- Osteoporotic comminution means tension-band wires cut out; consider a plate or a strong suture-based construct. Partial patellectomy with tendon repair remains a reasonable answer for an unreconstructable pole.
Management options
Non-operative treatment in a braceshowhide
Indication
Undisplaced fractures with an intact extensor mechanism, demonstrated by active straight-leg raise or active extension against gravity.
Implant design notes
No implant. Cylinder cast or a hinged knee brace locked in extension initially, then progressive controlled flexion.
Approach
Non-operative with functional progression.
Steps overview
- Aspirate a tense haemarthrosis if it aids assessment and comfort
- Test active extension and straight-leg raise to confirm extensor continuity
- Apply a brace locked in extension and allow weight bearing as tolerated
- Begin isometric quadriceps work and straight-leg raises immediately
- Unlock the brace progressively over four to six weeks
- Radiograph at two and six weeks to exclude progressive separation
Notes
Serial radiographs matter — a fracture that separates later needs surgery, and an unrecognised extensor mechanism failure produces permanent weakness.
Resident summary compiled from standard orthopaedic trauma teaching; verify against your departmental protocol.
Tension-band wiring with or without cannulated screwsshowhide
Indication
Displaced transverse fractures with two main fragments and a disrupted extensor mechanism.
Implant design notes
Two longitudinal Kirschner wires or two parallel cannulated screws with a figure-of-eight wire or heavy suture anterior to the patella. The quadriceps pull is converted into compression at the articular side during flexion. Passing the wire through cannulated screws gives a mechanically stronger and lower-profile construct.
Approach
Anterior midline longitudinal approach over the patella, with the articular reduction judged through the fracture or through a small medial arthrotomy.
Steps overview
- Supine with a tourniquet; longitudinal midline incision over the patella
- Evacuate haematoma and inspect and irrigate the articular surface
- Reduce the fragments anatomically, palpating the articular side to confirm no step
- Hold with a pointed clamp and place two parallel longitudinal wires or cannulated screws
- Pass the figure-of-eight wire or suture anteriorly, through the screws if used
- Tighten symmetrically on both limbs and bury the knot or twist
- Repair any retinacular tear on both sides
- Take the knee through gentle flexion on the table to confirm the construct holds, then start early motion
Notes
Prominent anterior hardware over subcutaneous bone commonly needs removal. Articular step-off is judged from inside the joint, not from the anterior surface.
Resident summary compiled from standard orthopaedic trauma teaching; verify against your departmental protocol.
Partial patellectomy with extensor repairshowhide
Indication
Unreconstructable comminution of one pole, most often the distal pole, where fixation cannot restore a congruent surface.
Implant design notes
Excision of the unreconstructable fragment with reattachment of the tendon to the remaining patella through bone tunnels or suture anchors, protected by a temporary tension-relieving cerclage in some techniques.
Approach
Anterior midline approach as above.
Steps overview
- Expose anteriorly and assess reconstructability of each fragment
- Excise the unreconstructable pole, preserving as much patella as possible
- Reattach the tendon close to the articular margin, not the anterior surface, to avoid tilting the patella
- Secure with heavy sutures through bone tunnels or anchors
- Protect the repair with a tension-relieving suture or wire if the repair is tenuous
- Repair the retinacula and rehabilitate with protected motion
Notes
Total patellectomy is a last resort with a substantial permanent extension deficit; preserve patella wherever possible.
Resident summary compiled from standard orthopaedic trauma teaching; verify against your departmental protocol.
Viva pearls
- The functional question is always the same: is the extensor mechanism intact? Test active extension or straight-leg raise and record it.
- Explain why the tension band works — flexion converts quadriceps distraction into articular-side compression.
- Judge articular reduction from inside the joint; a flush anterior surface can hide an articular step.
- Do not mistake a bipartite patella for a fracture — it is usually superolateral, has smooth sclerotic margins and is often bilateral.
- In a child, the sleeve fracture has minimal bony signs; look at patellar height on the lateral view and believe the clinical examination.
- Reattach the tendon near the articular margin after distal pole excision, or the patella tilts and articulates badly.
Sources for further reading
- Rockwood and Green's Fractures in Adults — patella and extensor mechanism
- Standard operative orthopaedics textbook — injuries of the knee extensor mechanism
- AO principles of fracture management — tension band principle
My labelled images · 1
Attach your own teaching radiographs with your own labels for pattern-recognition practice. Use anonymised study images only — never anything patient-identifiable.
Displaced Transverse patella fracture
Resident-authored study summary in original wording, not reproduced from copyrighted source text.