High Tibial Osteotomy (HTO): Medial Varus Unloading, Weight-Bearing and Rehab Progression
In short
High Tibial Osteotomy realigns bow-legged knees to preserve native cartilage and delay knee replacement. Learn osteotomy mechanics, bone healing timelines, and rehabilitation.
In this guide (5 sections)
The Biomechanical Rationale of High Tibial Osteotomy (HTO)
In patients with constitutional varus knee alignment ('bow legs'), the mechanical weight-bearing axis of the lower limb (the Mikulicz line) shifts medially, concentrating up to 70 to 80 percent of total knee joint loads through the medial compartment.
This accelerated asymmetrical overload causes isolated medial compartment cartilage loss and meniscal extrusion, while the lateral compartment remains completely pristine.
High Tibial Osteotomy (HTO) is a joint-preserving surgical realignment procedure: by creating a controlled wedge cut in the proximal tibia, the mechanical axis is shifted laterally into the healthy lateral compartment, offloading the medial cartilage and delaying total knee replacement by 10 to 15 years in active adults under 60.
Opening Wedge vs Closing Wedge HTO
Modern orthopaedic practice predominantly utilizes the Medial Opening Wedge HTO stabilized with rigid internal locking plates (e.g., TomoFix plate).
| Surgical Technique | Bone Cut & Fixation | Primary Advantage | Weight-Bearing Timeline | |
|---|---|---|---|---|
| 1. Medial Opening Wedge | Transverse cut from medial tibia; wedge opened with TomoFix plate | Single bone cut; precise angular correction; preserves bone stock | Partial Weight Bearing (PWB) for 6 weeks until bone callus forms. | |
| 2. Lateral Closing Wedge | Two cuts on lateral tibia; bone wedge removed; fibular osteotomy | Direct bone-to-bone contact; faster primary union | Early full weight bearing; higher peroneal nerve injury risk. |
Phase-Wise HTO Rehabilitation Milestones
Rehabilitation balances early joint range of motion with protecting the healing tibial osteotomy gap.
- Weeks 1 to 4 (Bone Protection Phase): Touchdown weight-bearing with crutches in a hinged knee brace locked in extension; active-assisted knee flexion strictly up to 90 degrees; isometric quadriceps and straight leg raises.
- Weeks 5 to 6 (Partial Weight-Bearing): Progress to 50 percent body-weight bearing with crutches, confirmed by early radiographic callus formation across the osteotomy gap; achieve full passive knee extension.
- Weeks 7 to 8 (Full Weight-Bearing Progression): Wean from two crutches to one crutch, then to independent walking as bone union progresses on follow-up X-rays; begin stationary cycling with light resistance.
- Months 3 to 6 (High-Load Functional Strengthening): Closed kinetic chain squats, step-ups, and balance drills; running and non-contact sports permitted once solid cortical bone bridging is radiographically confirmed.
Managing Post-Surgical Swelling and Gait Realignment
Following HTO, the patient leg alignment suddenly changes from bow-legged to slightly knock-kneed (valgus overcorrection of 2 to 3 degrees, which is intentional to protect the medial compartment).
Patients frequently feel 'crooked' during initial walking; physiotherapists provide visual mirror gait feedback and ankle-hip kinetic retraining to adapt to the new alignment.
Frequently Asked Questions
How long does the osteotomy bone cut take to heal?
Primary bone bridging across the opening wedge typically requires 6 to 8 weeks, with complete remodeling and solid cortical union achieved by 3 to 4 months.
Does having an HTO prevent having a total knee replacement later?
No. HTO is designed to delay knee replacement. If diffuse arthritis develops 10 to 15 years later, the patient can safely convert to a total knee arthroplasty (TKA).
Can bone graft be used in an opening wedge HTO?
Yes. In larger corrections (wedge gaps > 10 to 12 mm), surgeons frequently pack the osteotomy gap with autologous bone graft, allograft, or synthetic beta-tricalcium phosphate to accelerate bony union.
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