Crooked Leg (Knee)
What Is a Crooked Leg or Knee Malalignment?
A crooked leg describes a deviation of the mechanical axis of the lower limb — in other words, a malalignment of the knee. It has two main forms, and this page deals with malalignment in the adult knee; the physiological bowing seen in childhood, which usually corrects on its own, is a separate topic. A small amount of alignment variation is common and causes no pain or symptoms in most people. What matters is whether the deviation overloads one compartment of the knee.
- Varus (bow-leg, an “O” shape): with the ankles close together the knees fall apart, and most of the body weight passes through the inner (medial) compartment, which can become overloaded over time.
- Valgus (knock-knee, an “X” shape): the knees come together while the ankles separate, and body weight shifts to the outer (lateral) compartment, where loading increases.
In a healthy knee the load is spread evenly across the joint surface. When alignment is disturbed, load concentrates in one compartment and strains the cartilage, meniscus and ligaments on that side. For a general assessment of the knee and other knee conditions, the knee surgery overview is a useful starting point.
What Causes It and What Are the Risk Factors?
In adults the most common cause of malalignment is loss of cartilage and meniscus in one compartment; as the joint space on that side narrows, the axis is gradually pulled into varus or valgus. Previous fractures, especially tibial plateau fractures that heal out of alignment, can permanently change the axis. Meniscus insufficiency after a large tear or removal, congenital structural differences, bone-softening disorders and some developmental conditions can also affect alignment. Excess weight and repetitive loading of a single compartment are factors that speed the process up.
How Do the Symptoms Appear?
The bowed or knocked appearance of the legs is most often noticed while standing or walking. In cases that do cause symptoms, the usual complaint is pain in the overloaded compartment that increases with walking and stairs, along with swelling, stiffness and fatigue. Over time a sense of the knee “thrusting” outward or inward during walking, difficulty with balance and a shrinking walking distance may be added. A feeling of leg-length difference and one-sided wear of the shoe can also occur. Which movement makes the complaint worse, and how it affects daily function, is more informative than the appearance alone.
Which Problems Is It Associated With?
Malalignment is less a disease in itself than a background that leaves the knee open to other problems. Over time, knee osteoarthritis can develop in the overloaded compartment; the relationship works both ways, because cartilage loss also disturbs alignment. In a varus knee the lateral collateral ligament and posterolateral corner structures are placed under tension, while in a valgus knee the medial collateral ligament is strained. A ligament injury that changes the axis increases both instability and the risk of early wear. For this reason the state of the cartilage, meniscus and ligaments is reviewed together when alignment is assessed.
Diagnosis: Examination and Imaging
Assessment begins with observing stance and gait; the range of motion, tender points, ligament stability and the axis under load are examined. In imaging, weight-bearing (standing) knee X-rays are essential; in addition, a long-axis film that shows the whole leg in one frame is used to measure the mechanical axis and the degree of deviation. MRI is added in selected cases to show the state of the cartilage, meniscus and ligaments and to guide the surgical plan. The aim is not simply to see the deformity but to determine how much each compartment is loaded and whether correction is needed.
How Is Treatment Planned?
The treatment decision is personalised to the degree of deviation, the symptoms, the state of the cartilage, and the patient's age, activity level and expectations. Mild alignment differences that cause no symptoms are usually monitored. In cases that do cause symptoms, non-surgical measures are tried first; when these are not enough and the axis problem is driving the picture, surgical options come into consideration. No single method suits everyone; the aim is to reduce pain, preserve function and, where possible, help the joint last longer.
Non-Surgical Treatment Options
The main aim of the non-surgical approach is to relieve the loaded compartment and to support the joint by strengthening the muscles around the knee.
- Weight management and replacing overloading activities with suitable exercise.
- A personalised strengthening and balance programme that targets the front and back thigh muscles and the muscles around the hip.
- A trial, in selected cases, of a knee brace or in-shoe supports intended to shift load toward the opposite compartment.
- Management of pain and swelling with medication and, when appropriate, suitable injections.
Surgical Option: Osteotomy
In younger, active patients whose cartilage is largely preserved and who have an axis problem overloading one compartment, an osteotomy may be preferred. In this operation the bone is cut in a controlled way to correct the axis and shift load to the healthy compartment, and it is fixed with a plate and screws. This preserves the patient's own joint and can delay the need for a replacement. The method can be planned alongside cartilage or meniscus treatment as well as correcting alignment. Further detail is available on the knee osteotomy page.
Surgical Option: Partial or Total Replacement
If cartilage loss is confined to a single compartment and the other compartments and ligaments are sound, a partial (unicompartmental) knee replacement can correct the alignment and resurface the joint together. When wear has spread to more than one compartment, movement is restricted and advanced osteoarthritis has developed, a total knee replacement may be more suitable; the axis is also corrected during this operation. The choice between osteotomy and replacement is determined by age, the state of the cartilage, the degree of deviation, activity goals and associated problems. The treatment steps for knee osteoarthritis are covered on the knee osteoarthritis treatment page.
Recovery and Rehabilitation
Recovery depends on the operation performed. After an osteotomy the bone has to unite, so weight-bearing is gradual and controlled, and rehabilitation is built around range of motion, muscle strength and a balanced gait. After a replacement, movement and walking can usually begin earlier. In both cases the programme is planned individually, and progress is guided by goals reached rather than a fixed calendar. Prolonged immobilisation is avoided; steady, graded work improves the result.
When Should You See a Doctor?
Increasingly obvious bowing of the leg, pain concentrated in one compartment that does not settle with rest, a growing sense of “thrust” while walking, or progressive restriction of knee function all warrant a medical assessment. A marked deformity after sudden trauma, an inability to bear weight or clear instability should be assessed without delay. Early assessment allows planning at a stage when joint-preserving options are wider. To have a knee problem evaluated, you can contact Assoc. Prof. Serkan Sürücü.