If you have knee osteoarthritis, the focus is often on cartilage loss. It is also worth asking why the cartilage wore out, and alignment can be an important part of the answer.
Knee alignment determines how load is spread across the joint. Even minor malalignment can speed up cartilage wear in one area, which matters when weighing up treatment options.
At a Glance
- Bow-legged (varus) alignment overloads the inner side of the knee; knock-kneed (valgus) alignment overloads the outer side.
- Malalignment can create a cycle in which wear worsens the deformity and the deformity increases wear.
- Knee replacement can correct alignment, either to a neutral axis or to your own pre-arthritic alignment (kinematic alignment).
- Kinematic alignment may offer modest early benefits, but a lasting advantage has not been established.
- In younger people with arthritis in one compartment, an osteotomy may delay the need for a knee replacement.
What are varus and valgus alignment?
Varus alignment, often called bow legs, means the knee sits outwards relative to a line from the hip to the ankle. This shifts load onto the inner (medial) compartment of the knee, so the cartilage and meniscus there carry more than their share of force with every step. It is the most common pattern in knee osteoarthritis. As the inner compartment wears, the deformity can worsen, which increases the load further and creates a self-perpetuating cycle.
Valgus alignment, or knock knees, does the opposite and concentrates force on the outer (lateral) compartment. It is less common but, when significant, can overload the outer compartment and affect the kneecap joint.
Neither pattern is just cosmetic. Both can increase the load on part of the knee and contribute to cartilage damage.
How does knee replacement address alignment?
A total knee replacement is not just a resurfacing procedure. It is also an opportunity to correct the underlying mechanical problem. By removing the worn bone and cartilage and positioning the implants precisely, the alignment of the whole leg can be restored.
Traditionally, surgeons aimed to restore a neutral, straight alignment. This approach reduces pain, improves function and is well proven. However, thinking in this area has evolved.
What is kinematic alignment?
Kinematic alignment challenges the idea that every knee should be corrected to the same neutral line. Each person’s natural knee shape is different. Before arthritis developed, your knee had its own alignment, joint line angle and ligament balance.
Kinematic alignment aims to restore your pre-arthritic alignment and joint line. Some studies report modest early benefits compared with neutral (mechanical) alignment, but a lasting advantage in function or implant survival has not been established.
Image-based robotic systems, which plan the bone cuts from a CT scan taken before surgery, have made kinematic alignment more reproducible. The choice between mechanical and kinematic alignment is individual and depends on the degree of deformity, bone quality, ligament function and your surgeon’s judgement. You can read more about robotic knee replacement.
When is an osteotomy considered?
Not everyone with malalignment and knee arthritis needs a joint replacement, especially when arthritis is limited to one compartment and you are younger or more active.
In these situations, a high tibial osteotomy (HTO) or distal femoral osteotomy (DFO) may be a more appropriate first step. The shin bone (tibia) or thighbone (femur) is carefully cut and repositioned to move load away from the damaged compartment. You can read more about realignment osteotomy.
Osteotomy requires careful patient selection and rehabilitation. In some people, it can delay the need for a joint replacement for many years.
Summary
Alignment is an important factor in knee arthritis. Varus and valgus malalignment create predictable patterns of overload that can speed up cartilage wear. Knee replacement offers a chance to correct these mechanics, with kinematic alignment allowing a more personalised approach. When malalignment is significant and arthritis is early, osteotomy remains a joint-preserving option. The right strategy depends on your anatomy, deformity and goals.
If you would like to discuss how this applies to your knee, you can book a consultation with Dr Vishal Pai.
Frequently Asked Questions
How do I know if I have varus or valgus alignment?
A standing full-length X-ray (a long-leg alignment view) is the most reliable way to assess alignment. Your surgeon measures the line from your hip to your ankle and the angle between your thighbone and shin bone.
Can malalignment be corrected without surgery?
Physiotherapy, orthotics and activity changes can help manage symptoms and load, but they do not straighten the bones or correct fixed bony malalignment.
Is kinematic alignment right for everyone?
Not necessarily. People with very large deformities may not be suitable, because restoring their native anatomy may be technically difficult and could affect how long the implant lasts. Your surgeon will assess your anatomy.
What is the recovery like after a high tibial osteotomy?
Recovery from an HTO is more demanding than many people expect. Full weight-bearing is usually restricted for six to eight weeks while the bone heals, followed by structured rehabilitation. Many people return to sport within a year, although timing and level depend on healing, rehabilitation and the demands of the sport.
If I have an osteotomy, can I still have a knee replacement later?
Yes. A well-performed osteotomy does not rule out a later total knee replacement, although the conversion needs careful planning.
Wondering how alignment affects your knee?
Dr Vishal Pai assesses knee alignment and arthritis and performs realignment osteotomy and robotic knee replacement. You can arrange a consultation to discuss your options.
Written by Dr Vishal Pai
Vishal is an experienced knee surgeon based in Bayside, Melbourne. He consults at Sandringham Orthopaedic Specialists and operates at The Avenue Hospital and Calvary Holmesglen Private Hospital. His practice focuses on sports knee surgery, including ACL reconstruction and meniscal repair, as well as robotic knee replacement.