Knee varus (D, O-shaped legs, looped legs, arched legs, basket legs)
Overview
Knee varus refers to when heels and the palms of the feet are together, the lower limbs are naturally straightened or standing, with the knees and the medial malleolus touch, and the knees cannot be brought together, it is a common lower limb deformity. It occurs in children and adolescents. Knee varus is also known as arched legs, commonly known as “loop legs”, those with inverted legs are also known as O-shaped legs, and those with single lower limbs are called D-shaped legs. The incidence rate varies greatly from region to region. Generally speaking, cold regions are higher than warm regions.
O-shaped legs are medically called knee varus, commonly known as “loop legs”, “bow legs”, and “Luo basket legs”. Refers to the knee joint, the tibia of the calf has rotated inward by an angle, so it is called “knee varus.” The definition of knee varus is easy to be confused by seeing the shape of the lesion as it is taken for granted: the definition of knee varus is not named after the direction of the angle formed by the varus, but named after the turning direction of the shin tibia. Knee varus, the angle of the knee joint points to the outside, so it is often mistaken as knee valgus.
Definition (concept)
There is a valgus angle between the femoral shaft and the tibial shaft, which is a normal knee valgus.
Knee varus or knee valgus (FTA greater than 178 degrees, or FTA less than 172 degrees).
The angle between the normal longitudinal axis of the femur and the longitudinal axis of the tibia is 170°~179°. If it is greater than 180°, it is a varus deformity, and if it is less than 170, it is a valgus deformity.
The femoral and tibial angles can also be measured to determine knee varus or valgus.
There are not many changes in the femur of the knee varus deformity, and the main changes are in the tibia. The anatomical axis is at the midpoint of the femur passing through the chute of the patella, and the tibial anatomical axis passing through the midpoint of the intercondylar.
Causes of knee varus
There are many causes of knee varus, and more than 40 diseases are known to cause this deformity. In addition to the most common infantile rickets and adolescent rickets, there are also polio, epiphyseal injuries, fractures, and flat feet. Symptoms and other diseases that cause abnormal development of the femur or tibia, such as tuberculosis, tumors, cysts, and other knee varus deformities. The milder early-stage patients may not produce obvious symptoms, only affect the appearance, but severe symptoms can produce different symptoms, and due to lower limbs changes in the load-bearing line can lead to changes in the tension of ligaments and joint capsules, compensatory tibial deformities, degenerative osteoarthritis, patellar dislocation and patellar softening, etc., and cause corresponding symptoms.
The most common cause of O-leg formation
The most common causes of O-leg formation can be divided into three categories:
1. Developmental factors
During physical development, due to malnutrition or intestinal diseases, the lack of calcium and phosphorus and other nutritional elements, bone development disorders, bone deformation or articular cartilage dysplasia, and knee varus changes occur.
2. Unbalanced factors
Due to long-term bad posture or incorrect exertion habits, the muscle mechanics that innervates the joints are imbalanced. The long-term muscle mechanics imbalance can cause the joints to shift and cause knee varus. This kind of joint displacement is completely different from the well-known joint dislocation. The joint dislocation is manifested by the relative displacement of the corresponding two articular surfaces and the loss of normal correspondence. The joint displacement is mainly manifested by the rotation of the joint and the joint gap. Abnormal, in the knee joint, the patella rotates medially when the feet are parallel to each other. This is caused by the overall rotation of the knee joint, not the subluxation of the patella. As long as the joint is corrected, the patella will return to the front. It shows that the inner and outer gaps of the knee joint are not of equal width, and the inner gap is obviously narrowed.
3. O-legs caused by trauma or other diseases
The medial and lateral collateral ligaments of the knee joint are the stable structures of the medial and lateral angles of the knee joint, which can be adapted to the changes of the joint. In general, the medial and lateral collateral ligaments of the knee are not a key factor in the formation of O-shaped legs. However, in some cases, such as traumatic injury to the lateral collateral ligament, damage to the knee joint can also lead to O-shaped legs. It is more common, and surgery is usually required to repair damaged ligaments during treatment.
People with O-legs usually use muscles on the outside of the leg while standing and walking, but not on the inside. Therefore, the leg muscles are not well-developed, and there are often more lateral muscles and fewer inner muscles. In this way, the contours of the leg muscles formed are curved, giving the impression that the bones are curved. In fact, not all bones are bent, only a few are true bones. If you want to judge whether the bones are bent, the most straightforward way is to take an orthographic X-ray. In addition, part of the unbalanced O-leg is accompanied by the abduction and displacement of the hip joint at the same time, which will cause the gap between the legs to be particularly large.
4. Genetic factors