Periprosthetic Knee Fracture: Broken Bone Around a Knee Replacement
A periprosthetic fracture is a broken bone occurring directly around the components of a knee replacement, typically after a fall or injury in a patient with weakened bone. Mr Shakir Hussain, Consultant Orthopaedic Surgeon at the Royal Orthopaedic Hospital Birmingham, treats periprosthetic knee fractures with specialist surgical stabilisation or revision surgery, depending on implant integrity.
What is a periprosthetic knee fracture?
A periprosthetic knee fracture is a broken bone occurring in the femur or tibia directly around the components of a knee replacement. These fractures typically follow a low-energy fall in an older patient with osteoporosis, and their management is complex because treatment must address both the fracture and the status of the knee implant simultaneously.
The term "periprosthetic" means "around the prosthesis." In the context of a knee replacement, fractures most commonly occur in the distal femur (the lower part of the thigh bone, just above the femoral component) or the proximal tibia (just below the tibial component). Less commonly, they affect the patella (kneecap).
These fractures are more likely to occur around a knee replacement than around a normal bone for several reasons. The implant creates a zone of stress concentration at its tips, particularly at the anterior femoral notch. The bone adjacent to a well-fixed implant may weaken over time through a process called stress shielding, where the implant absorbs loads that would normally stimulate bone to maintain its density. Osteolysis from polyethylene wear debris can create lytic lesions in the periprosthetic bone that reduce its strength further.
The incidence of periprosthetic knee fractures is approximately 1 to 3 per cent, but this rises substantially in the elderly osteoporotic population and in those who have already had one or more revision procedures.
What are the symptoms of a periprosthetic knee fracture?
A periprosthetic fracture presents acutely after a fall or injury: sudden severe pain in or around the knee, immediate inability to bear weight, and often visible deformity or angulation of the leg. This is a surgical emergency requiring urgent orthopaedic assessment.
Sudden severe pain after a fall
The onset is abrupt, following a fall, trip, or direct trauma to the knee. The pain is severe and localised around the knee and lower thigh or upper shin, depending on the fracture site.
Immediate inability to bear weight
Unlike a soft tissue injury, a periprosthetic fracture makes weight-bearing on the affected leg immediately impossible due to mechanical instability of the bone around the implant.
Visible deformity or angulation
The leg may appear bent, shortened, or rotated compared to the other limb. This deformity reflects displacement of the fracture fragments and indicates that urgent reduction and stabilisation are needed.
Swelling and bruising
Significant haematoma (bruising) develops rapidly around the fracture site, extending from the lower thigh to the knee and often down the shin within the first 24 to 48 hours.
Shortened or rotated limb
Fracture displacement causes the distal fragment to rotate or shift, making the leg appear shorter or externally rotated compared to the uninjured side.
Pain on any movement
Any attempted movement of the knee causes severe pain. This distinguishes a periprosthetic fracture from soft tissue injuries around the knee, which typically allow some passive movement.
Who is at risk of a periprosthetic knee fracture?
Most periprosthetic knee fractures result from a low-energy fall in an older patient with osteoporosis. The bone around the implant is weakened by stress shielding and sometimes osteolysis. Anterior femoral notching at the time of primary surgery creates a stress riser at the distal femur that predisposes to fracture at that site.
Several factors increase the risk of fracture around a knee replacement:
- Osteoporosis. Reduced bone mineral density throughout the skeleton means less structural bone to support the implant. The compressive and bending forces that normally pass through bone after fracture can cause propagation into already weakened periprosthetic bone.
- Female sex and age over 70. Post-menopausal women with advancing age have the highest rates of osteoporosis and of falls. Periprosthetic fractures occur predominantly in this demographic.
- Anterior femoral notching. If too much anterior cortex of the distal femur is removed during the femoral bone preparation at primary surgery (inadvertent notching), the bone's resistance to bending forces at that point is substantially reduced, creating a predilection for supracondylar fracture.
- Prior revision surgery. Each revision procedure removes additional bone and leaves longer stem devices that shift the stress riser proximally. The risk of periprosthetic fracture increases with the number of previous surgeries on the same knee.
- Steroid use and inflammatory arthritis. Long-term corticosteroid use causes osteoporosis; inflammatory arthritis such as rheumatoid arthritis is independently associated with reduced bone density around joint replacements.
- Neurological conditions. Parkinson's disease, stroke, and other conditions causing balance impairment or muscle weakness increase the frequency of falls and therefore the fracture risk.
- Osteolysis. Large lytic lesions created by polyethylene wear debris can hollow out the periprosthetic bone, creating areas of catastrophic structural weakness that fracture even with minor trauma.
How is a periprosthetic knee fracture diagnosed?
Plain X-rays confirm the fracture and its location. CT scan is used to classify the fracture precisely and, critically, to assess whether the implant remains well-fixed or has loosened as a result of the fracture. This distinction determines whether fixation alone or revision knee replacement is the correct treatment.
Periprosthetic fractures are diagnosed and classified with a combination of imaging and clinical assessment:
- AP and lateral X-rays of the knee and femur/tibia. Confirm the fracture, its location, the degree of displacement and angulation, and whether the fracture line extends to the implant-bone interface. The Su classification (for distal femoral fractures) divides them into Type I (fracture proximal to the implant, well above), Type II (fracture reaching the implant tip), and Type III (fracture distal to the implant).
- CT scan. Essential when the fracture pattern on plain film is complex, when implant loosening is suspected, or when surgical planning requires precise fracture mapping. CT can demonstrate whether the implant has migrated or subsided as a result of the fracture, confirming loosening that would necessitate revision rather than fixation.
- Assessment of neurovascular status. The popliteal artery and tibial and common peroneal nerves are at risk in displaced periprosthetic fractures. Pulses, capillary refill, and sensation in the foot must be assessed urgently before and after reduction.
The single most important clinical decision is whether the implant is well-fixed or loose. A well-fixed implant can be left in place and the fracture fixed around it. A loose implant must be revised at the same operation, as fixation with a loose implant in situ is very likely to fail.
How is a periprosthetic knee fracture treated?
If the implant is well-fixed, the fracture is stabilised with internal fixation (locking plate or intramedullary nail) without disturbing the replacement. If the implant is loose, revision knee replacement with long-stemmed implants bypasses the fracture and restores fixation in a single procedure.
Internal Fixation (Locking Plate or Nail)
A distal femoral locking plate is the most commonly used device for supracondylar periprosthetic fractures. Locking screws angle around the implant within the distal fragment, providing stable fixation. An intramedullary nail can be used where the femoral component design allows passage of the nail. Both techniques achieve fracture stability while leaving the well-fixed implant undisturbed.
- Implant preserved in situ if well-fixed
- Distal femoral locking plate most commonly used
- Intramedullary nail where implant geometry allows
- Early mobilisation with protected weight-bearing
- Bone union typically confirmed at 6 to 12 weeks
Revision Knee Replacement with Long Stems
If the fracture has destabilised the implant, or if pre-existing loosening is confirmed, revision knee replacement using long-stemmed components is the definitive treatment. Long tibial and femoral stems bypass the fracture zone entirely, anchoring in healthy diaphyseal bone well proximal and distal to the fracture. This provides immediate mechanical stability, restores the joint surface, and avoids the prolonged non-weight-bearing required for fracture fixation alone in a loose implant situation.
- Loose implant and fracture addressed in a single operation
- Long stems bypass the fracture into healthy diaphyseal bone
- Augments and constrained components added as required
- Definitive joint reconstruction at the time of fracture surgery
- Avoids two-stage approach of fixation then later revision
Specialist expertise in periprosthetic knee fracture surgery in Birmingham
Consultant at the Royal Orthopaedic Hospital
Mr Hussain practises at the Royal Orthopaedic Hospital Birmingham, one of the largest specialist orthopaedic hospitals in Europe, with 24/7 trauma capability and the full range of revision implant systems for complex periprosthetic fracture management.
3,000+ arthroplasty cases from 5,000+ procedures
A high operative volume including complex primary and revision cases. Read more about Mr Hussain's training and background.
MAKO, ROSA, and CORI robotic certifications
Robotic assistance supports pre-operative digital planning for complex revision cases where altered anatomy and bone loss require precise stem selection and positioning.
Complex revision surgery expertise
Mr Hussain performs revision knee replacement for the full spectrum of failure modes, including periprosthetic fracture. See the revision surgery page for full details.
Doctify Outstanding Patient Experience 2024, 2025, and 2026
Awarded in three consecutive years, recognising consistently high patient-reported outcomes and communication throughout the surgical journey.
4.98 out of 5 from verified reviews on Doctify. Outstanding Patient Experience Award 2024, 2025, and 2026.
Frequently asked questions about periprosthetic knee fracture
For more questions about surgery, recovery, fees, and what to expect, see the full frequently asked questions page or read recent patient testimonials.