Correcting the leg axis
Correcting the axis of the leg
The load-bearing axes of the legs have a very large influence on the pressure inside the knee joint. A bow-leg deformity increases the contact pressure on the inner side, while a knock-knee deformity increases the contact pressure on the outer side.
Where there is cartilage damage in the affected part of the joint, or where signs of wear are already present, it may be necessary to correct this malalignment.
These techniques make it possible to slow the course of osteoarthritis considerably – both combined with the treatment of cartilage damage and on their own where there are signs of wear.
Different rules apply in children and adolescents: there, bow legs and knock knees are often part of normal development, and as long as growth remains the axis can be corrected through it. There is a page of its own for that: bow legs and knock knees in children.
What happens when the leg axis is corrected?
Young patients, a large challenge
While life expectancy in our society continues to rise, more and more young people are also showing clear signs of wear in the knee joint. The cause is frequently a high level of sporting activity. This group is particularly difficult: because of their high demands on mobility and function, and their long life expectancy, classic joint replacement is not a suitable option for them – the lifespan of a knee prosthesis is currently around 30 years.
Risk factors and overloading
The literature names numerous risk factors for cartilage damage: age, sex, sporting or occupational load, excess weight (a high BMI) and earlier injuries are among the most common causes. What they all have in common is a mechanical or biomechanical overload of the knee joint. While moderate loading is essential for preserving joint function, excessive pressure leads to the death of the cartilage cells (chondrocytes) and to the release of inflammatory substances.
Malalignment as the cause
It is known today that it is frequently not the cartilage damage itself but the underlying abnormal loading – through a deviation of the leg axis, for example – that is the real cause of osteoarthritis developing. It is therefore not enough to reconstruct only damaged structures such as cruciate ligaments or menisci. Correcting the leg axis is decisive in achieving lasting relief and a stable joint.
Why the leg axis matters
The alignment of the legs – whether bow-legged (varus) or knock-kneed (valgus) – has a considerable influence on the pressure inside the knee joint. Even a slight varus deviation of 3 to 5° can mean that up to 90 % of the load acts on the inner part of the joint (the medial compartment). Comparable effects are seen in the outer part of the joint with a valgus deformity. A surgical correction of the axis can even out this uneven loading for the long term.
Diagnosis
Before correcting the axis we take full-length standing X-rays, which allow us to analyse the exact deviation. This shows whether the deformity arises in the thigh or in the lower leg. We then plan the operation precisely with calibrated software – including the angle of correction and the appropriate implant. In more complex cases a combined correction of thigh and lower leg may be necessary.
Symptoms
Pain
Cartilage damage and wear lead to pain that depends on load
Swelling
Cartilage debris irritates the joint, which responds by producing fluid
Warmth
The increased blood flow to the irritated joint makes it feel warmer
The knee joint in detail
Rotate the 3D model and explore the structures
Loading 3D model…
Treatment options for a malaligned leg axis
Treatment options
Surgical procedures for correcting the leg axis
Medial opening-wedge high tibial osteotomy (HTO) for valgus correction
The tibia is opened from the inner side in order to correct a bow-leg deformity
Medial closing-wedge distal femoral osteotomy for varus correction
Correction of a knock-knee deformity by removing a wedge from the inner side of the thigh bone
Rotational osteotomy of the distal femur
Correction of rotational deformity by an osteotomy on the inner side of the thigh bone
Slope correction
A wedge is taken from the lower leg in order to correct the slope of the tibia
Our knee specialists
Experienced consultants for leg axis correction and knee surgery
