A high tibial osteotomy (HTO) is a surgical procedure that reshapes the top of the shinbone to shift weight away from a damaged part of the knee. It’s primarily used for people with arthritis on the inner side of the knee, where years of uneven loading have worn down the cartilage. By cutting and repositioning the bone, the surgeon redirects the mechanical forces through the healthier outer compartment, relieving pain and slowing further joint deterioration.
How the Procedure Works
In a normally aligned leg, your body weight passes fairly evenly through the knee joint. When the inner (medial) side of the knee develops arthritis, the cartilage thins and the leg gradually bows inward, concentrating even more force on the damaged area. HTO breaks this cycle by cutting a wedge-shaped section into the upper tibia and adjusting the angle so the leg’s weight-bearing line shifts slightly toward the outer side of the knee.
There are two main techniques. In an opening wedge osteotomy, the surgeon cuts the bone on the inner side of the tibia and opens a gap, which is held in place with a metal plate and screws. The gap fills in with new bone over time, and some cases use a bone graft to help this process along. In a closing wedge osteotomy, a wedge of bone is removed from the outer side and the gap is closed, shortening that side of the tibia to achieve the same angular correction.
Neither technique has proven clearly superior. Opening wedge osteotomies allow more precise correction of the angle, but they carry a higher risk of the bone healing slowly (nonunion) and sometimes require bone grafting. Closing wedge osteotomies tend to heal more reliably, but they involve work near the fibula and carry a small risk of nerve injury on the outer side of the leg. The choice often comes down to the surgeon’s experience and the specifics of your anatomy.
Who Is a Good Candidate
The ideal candidate is a middle-aged person, generally under 65, with arthritis limited to the inner compartment of the knee, good range of motion, and stable ligaments. HTO is particularly appealing for active people who want to continue physical activities that a joint replacement might not fully support. Most surgeons consider it more appropriate than partial knee replacement for patients who are overweight, though the effect of body weight on long-term results is still debated.
Several factors make the procedure less likely to succeed. These include:
- Severe joint destruction on X-ray
- Age over 65
- Advanced arthritis behind the kneecap
- Limited knee bending (less than 90 degrees of motion)
- Significant stiffness where the knee can’t fully straighten (15 degrees or more of contracture)
- Ligament instability or lateral thrust when walking
- Rheumatoid arthritis
HTO Compared to Knee Replacement
HTO and knee replacement solve the same problem differently. Knee replacement removes the damaged surfaces and substitutes artificial ones. HTO preserves your natural joint and buys time before a replacement becomes necessary.
In direct comparisons, HTO patients tend to achieve better range of motion and slightly better knee scores than those who receive a partial knee replacement. Functional outcomes between the two groups end up similar. The key advantage of HTO is that it keeps the door open: if the knee eventually wears out further, a total knee replacement can still be performed later. One trade-off is that converting an osteotomy to a total knee replacement can be more technically challenging than a first-time replacement, particularly after a closing wedge procedure.
What Recovery Looks Like
After surgery, you’ll use crutches and limit how much weight you put on the leg. A standard protocol restricts you to very light weight bearing (around 10 to 15 kilograms, roughly the weight of resting your foot on the floor) for the first six weeks. Some surgeons now allow a faster progression, with patients reaching full weight bearing in about four weeks on average if pain and wound healing allow.
Under a standard timeline, most patients walk without crutches or any support within six months. With an accelerated protocol, patients typically ditch crutches within three months. The bone itself takes several months to fully heal and remodel. During this period, high-impact activities like running or jumping are off limits. Your surgeon will track bone healing with follow-up X-rays before clearing you for more demanding activities.
Potential Complications
Like any bone surgery, HTO carries risks. The most common concern with an opening wedge technique is delayed bone healing. Patients whose osteotomy is slow to consolidate are significantly more likely to develop further complications. In some cases, the bone fails to heal entirely, a condition called nonunion, which may require additional surgery.
Hardware irritation is another frequent issue. The metal plate sits just beneath the skin on the inner side of the tibia, and it can cause localized pain, particularly where tendons cross over it. This discomfort typically resolves once the hardware is removed after the bone has fully healed. Nerve-related symptoms, such as numbness or tingling on the outer side of the lower leg, can occur with either technique, though the risk of serious nerve injury is higher with the closing wedge approach because of its proximity to the peroneal nerve.
When a bone graft is harvested from the patient’s own pelvis, the donor site itself can be a source of pain and complications. Using donor bone (allograft) or synthetic fillers instead, particularly for smaller corrections, avoids this problem.
How Long the Results Last
A large study following 455 patients for up to 19 years found that 95% of osteotomies were still functioning well at 5 years, meaning patients had not gone on to need a knee replacement. At 10 years, that number dropped to 79%, and at 15 years it was 56%. In practical terms, HTO gives most people a solid decade or more of improved function before a knee replacement enters the conversation, and for many it lasts considerably longer.
Achieving the correct alignment during surgery is the single biggest predictor of durability. The surgical goal is typically around 3 to 4 degrees of slight outward angulation (valgus). Patients who don’t reach this target are more likely to see their correction gradually drift back toward its original alignment over the following years, which accelerates cartilage wear and shortens the lifespan of the procedure. Modern locking plates provide more rigid fixation than older hardware designs, which helps maintain the corrected angle during healing.