Knee alignment is a common topic of curiosity, especially for those who notice their knees move inward, a posture frequently called “knock-knees.” This alignment, medically termed genu valgum or knee valgus, involves the knee joint angling toward the midline of the body. While it is a distinct feature of a person’s lower limb structure, the presence of this alignment does not automatically mean a person is destined for pain or injury. Understanding whether this structure presents a problem depends entirely on distinguishing between how the knees rest and how they move under load. The potential for harm is related to the control and stability demonstrated during physical activity, not the resting position itself.
Defining Static and Dynamic Knee Valgus
To determine if knee valgus is a concern, it is necessary to distinguish between two different presentations. Static knee valgus refers to the fixed, anatomical alignment of the knee when a person is standing still, often resulting from congenital factors or bone shape. This fixed alignment is not typically associated with pain or functional limitations unless the deviation is severe.
Dynamic knee valgus, in contrast, is an uncontrolled movement pattern where the knee collapses inward during activities like running, jumping, or squatting. This movement is a combination of hip adduction and internal rotation, which drives the thigh bone inward, creating the “knock-kneed” appearance under load. The dynamic presentation is what most concerns clinicians because it exposes the knee to abnormal forces that can increase the risk of injury.
Underlying Causes of Valgus Alignment
The reasons a person may exhibit valgus alignment fall into two primary categories: structural and functional. Structural causes relate to the non-modifiable, inherent geometry of the bones and joints. This can include genetic predisposition, the angle of the hip bone (known as coxa valga), or developmental conditions like rickets or Blount’s disease.
Functional causes are modifiable and stem from muscle imbalances and poor movement control throughout the lower body. The most common contributing factor is weakness in the hip abductor and external rotator muscles, particularly the gluteus medius and gluteus maximus. These muscles are responsible for stabilizing the pelvis and preventing the thigh bone from rotating inward during single-leg stance or landing.
Another significant functional contributor is poor foot mechanics, such as excessive pronation or “flat feet.” When the foot collapses inward, it can create a chain reaction up the leg, forcing the shin bone to rotate internally and contributing to the inward collapse of the knee.
When Knee Valgus Becomes a Problem
The presence of dynamic knee valgus is a risk factor for several common lower extremity injuries, especially in active individuals. The inward collapse places excessive stress on the structures of the knee joint. One primary problem is an increased risk of non-contact Anterior Cruciate Ligament (ACL) tears.
The mechanism for this tear involves the combination of hip internal rotation and knee inward movement, which places extreme shear and rotational forces on the ACL, particularly during rapid deceleration or landing. Dynamic valgus is also associated with Patellofemoral Pain Syndrome (PFP), often referred to as runner’s knee. This condition is characterized by pain around or under the kneecap due to abnormal tracking and increased pressure on the joint cartilage.
Over time, this altered biomechanics can lead to premature wear on the knee joint. The chronic inward angle can overload the cartilage and soft tissues on the outer (lateral) side of the knee, potentially contributing to lateral compartment arthritis or medial ligament irritation. The uncontrolled nature of dynamic valgus during athletic movements increases susceptibility to both acute injury and chronic pain.
Strategies for Correction and Management
Addressing problematic dynamic knee valgus focuses primarily on improving neuromuscular control and muscular strength. A primary strategy involves targeted strengthening of the hip stabilizing muscles, which are often weak in people exhibiting this movement pattern. Exercises like side-lying clam shells, glute bridges, and lateral step-downs specifically target the gluteus medius and maximus to improve the hip’s ability to resist inward collapse.
Incorporating single-leg stability exercises, such as single-leg deadlifts or squats, is also beneficial as they train the body to maintain proper alignment while bearing weight. These functional movements help integrate hip and knee control, which is essential for activities like running and jumping. Mobility work is equally important, focusing on stretching tight muscles like the hip flexors and adductors, which can pull the hip into an unfavorable position.
Furthermore, managing underlying foot mechanics through supportive footwear or custom orthotics can help create a more stable base of support. These devices can reduce excessive foot pronation, thereby lessening the internal rotation forces that travel up the leg to the knee. For a precise and personalized plan, consulting a physical therapist or sports medicine physician is recommended, as they can perform a thorough gait analysis and create an intervention program tailored to the individual’s specific movement impairments.