Genu Recurvatum Following Revision Knee Arthroplasty: Eccentric Quadriceps Retraining

Genu recurvatum, or pathological knee hyperextension beyond neutral zero degrees, is a challenging sagittal plane complication encountered following revision total knee arthroplasty. It frequently results from extensive posterior capsular release during previous surgeries, distal femoral bone over-resection, undersized femoral components, or severe quadriceps and gastrocnemius muscle weakness. In the normal gait cycle, the knee absorbs ground reaction forces by flexing 10 to 15 degrees during loading response. When recurvatum occurs, the knee snaps backward into hyperextension upon heel strike, locking against the posterior capsule and transferring destructive shear forces directly onto the prosthetic constraint post and fixation stems. Physiotherapy must focus on restoring eccentric quadriceps control, dynamic hamstring co-contraction, and proprioceptive stance awareness.

Domestic and Cultural Indian Realities

Living with genu recurvatum in an Indian household presents significant balance and joint preservation challenges. Walking barefoot on smooth marble or polished vitrified tiles removes heel cushioning, increasing the impact shock that triggers uncontrolled backward knee locking. Patients must wear supportive indoor footwear with a slight heel raise (approximately 1 to 1.5 cm) to encourage early knee flexion during stance. Floor sitting in sukhasana and squatting are strictly contraindicated, as deep flexion followed by forceful unassisted standing overstretches the posterior capsule. Bathrooms must be equipped with an elevated western commode at 20 inches height with solid support grab rails. In narrow internal stairways, patients must use handrails and descend with a step-to pattern to avoid sudden backward joint snaps.

Clinical Biomechanics and Reconstructive Fixation

The biomechanical hazard of genu recurvatum in a revision knee prosthesis is anterior edge loading and posterior constraint wear. When the knee hyperextends beyond neutral, the anterior lip of the polyethylene insert pinches against the femoral component, while the posterior capsule and popliteal structures undergo excessive tensile stretching. Over thousands of gait cycles, this repetitive hyperextension loading loosens the tibial baseplate and damages the central constraint post. Restoring neuromuscular control requires shifting reliance away from passive structural locking toward active muscular braking. Eccentric quadriceps strengthening trains the knee extensors to absorb ground reaction loads in slight flexion, while hamstring strengthening prevents uncontrolled terminal knee extension.

Rehabilitation Assessment and Functional Progression

Clinical assessment measures passive hyperextension in supine using a goniometer, dynamic recurvatum during stance phase, and quadriceps lag. An extension-stop hinged knee brace or Swedish knee cage orthosis is often prescribed initially to physically block hyperextension beyond zero degrees during community ambulation. Gait retraining with mirror biofeedback teaches the patient to maintain a soft knee (2 to 5 degrees of deliberate flexion) throughout the midstance phase. Weight-bearing exercises transition from bilateral support to single-leg stance drills as eccentric control develops.

Targeted Rehabilitation and Joint Preservation Exercises

Rehabilitation prioritises eccentric quadriceps training, closed-chain hamstring curls, and backward walking drills that naturally enforce knee flexion.

Red Flags and Immediate Surgical Escalation

A sudden sensation of the knee giving way accompanied by an audible pop, severe joint instability, or visible posterior tibial sagging indicates catastrophic disruption of the posterior cruciate substitution mechanism or fracture of the polyethylene constraint post, requiring urgent orthopaedic evaluation.

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