Periprosthetic Knee Fracture Rehabilitation: Lewis-Rorabeck Classification Protocols

Periprosthetic fractures around a total knee arthroplasty (TKA) represent serious, escalating orthopaedic emergencies, with the distal femur representing the most common fracture site (occurring in up to 2.5% of primary knee replacements and 5% of revisions). Typically caused by low-energy falls in elderly osteoporotic patients, these fractures are classified using the Lewis-Rorabeck system into Type I (non-displaced fracture with a well-fixed, stable prosthesis), Type II (displaced fracture with a stable prosthesis amenable to anatomical reduction and lateral locking plate fixation or retrograde intramedullary nailing), and Type III (fracture associated with a loose or failed prosthesis, requiring complex revision arthroplasty with a long-stem modular implant). Physiotherapy must balance early joint mobilization to prevent arthrofibrosis with strict adherence to weight-bearing restrictions dictated by implant stability and bone quality.

Domestic and Cultural Indian Realities

Rehabilitating an elderly Indian patient with a periprosthetic knee fracture requires extensive home safety adaptations. Deep squatting for traditional Indian commodes places massive shear and rotational stress across the implant-bone interface, risking catastrophic loosening; an elevated western commode chair must be installed over the squat toilet. Traditional low floor sitting (sukhasana) during prayer, dining, or family gatherings is strictly contraindicated; patients must sit in high dining chairs and use an elevated pooja chowki. Sagging rope charpoys must be elevated with wooden riser blocks and reinforced with rigid plywood beneath the mattress to achieve a 20-inch transfer height that avoids perilous hip and knee flexion during standing. Navigating uneven courtyard thresholds, wet bathroom floors, or climbing steep stairs without railings presents severe fall risks; patients must use a walker with wheels and have grab bars installed in bathrooms.

Clinical Biomechanics and Anatomical Healing

A total knee replacement alters the natural load distribution across the distal femur, creating a point of stress concentration (stress riser) at the junction between the stiff femoral prosthetic shield and the native osteoporotic bone above it. In Type II fractures with a well-fixed prosthesis, lateral precontoured locking compression plates span the fracture and grip the distal condylar bone using multi-axial screws that weave around the femoral prosthesis box. In Type III fractures, the loose femoral component acts as a destructive lever within the canal, requiring extraction and replacement with a cemented or fluted modular stem that bypasses the fracture by at least two femoral diameters to achieve stable diaphyseal engagement. Premature full weight-bearing causes cantilever bending stress that can loosen the plate or shear the stem before biological integration occurs.

Validated Special Tests and Differential Diagnosis

Clinical examination checks for rotational alignment, extensor mechanism continuity, and patellar tracking. The stability of the TKA prosthesis is assessed on serial radiographs, looking for radiolucent lines greater than 2mm, component subsidence, or tilt. Inflammatory blood markers (ESR, CRP) and joint fluid aspiration rule out periprosthetic joint infection (PJI), which is present in up to 10% of periprosthetic fractures. Differential diagnosis distinguishes pure periprosthetic supracondylar fractures from patellar component fractures and tibial tray disruptions.

Stage-by-Stage Functional Recovery Protocol

Phase 1 (Weeks 0 to 6 post-op) maintains the knee in a hinged brace locked in full extension for transfers and ambulation, unlocking for passive and active-assisted range of motion from 0 to 60 degrees. Weight-bearing is strictly non-weight bearing or touch-down (less than 10 kg) with a walker. Phase 2 (Weeks 6 to 12) unlocks the brace to 90 degrees, introducing seated active-assisted heel slides, static quadriceps sets, and progressive partial weight-bearing (starting at 25% and advancing by 25% every two weeks) once bridging callus is radiographically confirmed. Phase 3 (Weeks 12 to 24) advances to full unassisted weight-bearing, weaning from the walker to a single stick, and closed-chain functional knee stability training.

Red Flags and Urgent Surgical Indicators

Seek immediate orthopaedic assessment if you experience a sudden feeling of mechanical instability, clicking, or inability to support weight on the operated knee, signaling plate pullout or prosthetic component loosening. Spreading redness, warmth, or persistent drainage from surgical scars indicates deep periprosthetic infection requiring urgent joint debridement. Severe calf swelling, calf tenderness, or sudden shortness of breath signals deep vein thrombosis or pulmonary embolism.

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