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Overview & Indications
Knee arthrodesis (fusion of the knee joint in a fixed position) sacrifices all knee movement but provides a stable, pain-free extremity capable of weight-bearing. It is generally considered a procedure of last resort — reserved for cases where arthroplasty has irretrievably failed, or where arthroplasty cannot be performed due to infection, oncological resection, or severe neuromuscular dysfunction. Despite its limitations, a well-performed arthrodesis can restore function and independence in a carefully selected patient.
Primary indications for knee arthrodesis: (1) failed total knee arthroplasty (TKA) with chronic peri-prosthetic joint infection (PJI) not amenable to re-implantation (most common indication); (2) failed TKA with severe bone loss and inadequate soft tissue envelope precluding revision arthroplasty; (3) destructive septic arthritis of the native knee; (4) post-traumatic arthritis in a young heavy manual worker where TKA longevity is insufficient; (5) severe neuromuscular disease with inadequate quadriceps function to control a TKA; (6) oncological resection (distal femur or proximal tibia) where an endoprosthesis is not appropriate
Failed TKA with PJI is now the most common indication — when a two-stage revision arthroplasty is not possible (persistent infection despite spacer, resistant organisms, inadequate bone and soft tissue, patient comorbidities), arthrodesis provides a reliable alternative to amputation
Contraindications: ipsilateral hip or ankle arthritis (arthrodesis eliminates knee motion which increases compensatory stress at adjacent joints); contralateral limb problems; poor bone stock (fusion may fail); significant soft tissue deficiency
Optimal Position for Fusion
Optimal fusion position: 0–10° of flexion (functional extension — avoids hyperextension which causes gait instability and increases energy consumption); 5–7° of valgus (neutral to slight valgus — mirrors normal anatomical alignment); neutral to slight external rotation (5–10°); functional limb length — the fused extremity should ideally be 1–2 cm shorter than the contralateral side to allow foot clearance during swing phase; positioning in these parameters produces the most efficient gait pattern and minimises energy expenditure
Fusion in excessive flexion causes significant energy cost during gait (hip flexors must work harder to advance the limb) and poor cosmesis; fusion in varus creates medial thrust and accelerates ipsilateral hip and ankle OA
Surgical Techniques
Technique
Description
Advantages / Disadvantages
Intramedullary nail (long stemmed)
A long intramedullary nail passes from the hip (through the greater trochanter) or the distal femur, through the knee joint, and into the tibia; the nail spans the entire femur-tibia unit and provides rigid fixation
Highest fusion rates (85–100%); allows early weight-bearing; gold standard for most cases; the nail must pass through the knee into the tibia — this is technically demanding when there is severe bone loss; the long nail distributes load along the entire limb, reducing stress shielding
External fixator (Ilizarov / circular frame)
A circular or monolateral external fixator spans the knee and applies compression across the fusion site; can be used with bone transport for significant bone defects
Preferred for infected cases (avoids internal implant in contaminated field); allows simultaneous bone transport for large defects; high pin site infection rate; bulky; prolonged treatment duration; lower fusion rate than IM nail if bone loss is not addressed
Dual compression plating
Two plates (one medial, one lateral or anterior) applied across the knee joint to achieve compression and rigid fixation
Good fixation; can address deformity; not appropriate in infected or contaminated cases; less commonly used as primary technique since IM nailing became standard
Infected TKA arthrodesis with bone loss: when PJI has caused significant distal femoral and proximal tibial bone loss (common after multiple revision surgeries), the IM nail alone may not achieve adequate bony contact for fusion; options include: (1) bulk structural allograft to fill the defect before nailing; (2) Ilizarov frame with bone transport (tibia or femur transported through the defect over weeks — the most reliable method for large segmental bone defects); (3) a custom modular IM nail spacer (megaprosthesis-type) bridging the defect and achieving fusion if viable bone is available at both ends
Outcomes & Complications
Non-union: the most significant complication; rates vary from <5% with IM nailing and adequate bone contact to 20–30% in cases with significant bone loss or persistent infection; risk factors — active infection, poor bone stock, smoking, diabetes, steroid use, inadequate fixation
Gait after arthrodesis: patients with a well-positioned knee arthrodesis ambulate with a characteristic gait — circumduction of the stiff limb during swing phase (to achieve foot clearance); energy expenditure during walking is increased by approximately 30–40% compared to normal; most patients achieve independent community ambulation with or without an aid; a shoe raise on the fused side (1–2 cm) improves foot clearance and reduces circumduction
Ipsilateral hip and ankle OA: long-term complication; the loss of knee motion transfers stress to adjacent joints; particularly significant if the contralateral hip or knee also has arthritis
Infection: persistent or recurrent PJI after arthrodesis; managed with prolonged antibiotics; rarely requires amputation
Implant failure: nail fracture or backing out in long IM nails; more common in non-union cases with continued motion at the fusion site
Amputation vs arthrodesis: in cases of failed TKA with chronic PJI where arthrodesis is not feasible (inadequate bone stock for fusion, persistent virulent infection, uncontrolled sepsis), above-knee amputation (AKA) may be the only option; AKA has a higher mortality in this patient population and a very poor functional outcome (rehabilitation with a prosthetic limb in an elderly comorbid patient is limited); arthrodesis is strongly preferred over amputation when technically achievable
Consultant-Level Considerations
Two-stage revision vs arthrodesis for infected TKA: the decision between attempting a two-stage revision (resection arthroplasty spacer, antibiotic treatment, then re-implantation of a new TKA) and arthrodesis depends on: organism virulence (highly resistant organisms — MRSA, fungal PJI — favour arthrodesis); number of prior revision attempts; bone and soft tissue quality; patient age, functional demand, and medical comorbidities; patient preference (mobility vs stability); a successful two-stage revision preserves movement and function but carries the risk of re-infection and further procedures; arthrodesis provides a definitive infection-free result with no further implant but at the cost of knee movement
Ilizarov frame for bone transport after knee arthrodesis: when large segmental bone loss is present (e.g., after removing an infected distal femoral or proximal tibial component), the Ilizarov technique can transport a regenerate segment across the defect; corticotomy is performed at a well-vascularised metaphyseal site, and the segment is slowly transported (1 mm per day) to fill the defect; this process takes many months but can fill defects of 5–15 cm without the need for bulk allograft; the reconstructed limb is then fused with an IM nail
Knee arthrodesis in oncology: resection of the distal femur or proximal tibia for bone tumours (osteosarcoma, giant cell tumour) can be reconstructed with an endoprosthesis (megaprosthesis), osteoarticular allograft, or arthrodesis; arthrodesis is reserved for cases where endoprosthesis is not appropriate (prior infection, very young child with significant growth remaining, failed endoprosthesis); provides excellent durability but sacrifices knee motion; discussed in conjunction with the limb salvage article
Functional outcomes and patient satisfaction: patient satisfaction after knee arthrodesis is generally high in the context of long-standing PJI — relief from infection and pain outweighs the loss of movement in most patients; quality of life scores improve significantly after arthrodesis compared to the pre-operative state of chronic infection; careful pre-operative counselling about the permanent nature of the procedure and the expected gait pattern is essential
Exam Pearls
Most common indication: failed TKA with chronic PJI not amenable to revision arthroplasty; procedure of last resort before amputation
Optimal fusion position: 0–10° flexion; 5–7° valgus; neutral rotation; 1–2 cm shortening for foot clearance during swing phase
Long IM nail: gold standard technique; highest fusion rates (85–100%); spans entire femur-tibia unit; allows early weight-bearing
External fixator: preferred for infected cases — avoids internal implant in contaminated field; Ilizarov for large bone defects with transport
Gait after arthrodesis: circumduction during swing phase; ~30–40% increased energy expenditure; shoe raise 1–2 cm on fused side; most achieve independent community ambulation
Non-union: most significant complication; higher with bone loss, active infection, smoking, diabetes; IM nail reduces risk vs external fixation
Amputation vs arthrodesis: arthrodesis strongly preferred; AKA has higher mortality and poor functional outcomes in the elderly comorbid patient
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References
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Gottfriedsen TB et al. Knee arthrodesis after failure of knee arthroplasty. J Bone Joint Surg Am. 2016.
Bargiotas K et al. Arthrodesis of the knee with short-term, high-dose parenteral antibiotic therapy after infected total knee arthroplasty. J Bone Joint Surg Am. 2006.
Yeoh D et al. Knee arthrodesis with the Ilizarov frame for the treatment of infected knee arthroplasty. J Arthroplasty. 2008.
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Rockwood and Greens Fractures in Adults. 9th Edition. Wolters Kluwer.
Orthobullets — Knee Arthrodesis.
Incavo SJ et al. Knee fusion using a long intramedullary nail. J Arthroplasty. 2000.
Farid YR et al. Simultaneous bone transport and knee arthrodesis using the Ilizarov method. J Orthop Trauma. 2009.
