Genu Valgum (Knock Knees)
Knock knees, where the knees angle inward
Quick Facts
- Type: Lower-limb alignment condition
- Main feature: Knees touch, ankles apart
- Often normal in: Children aged about 3 to 5 years
- When to assess: Severe, one-sided, painful, or worsening cases
Overview
Genu valgum, commonly called knock knees, describes a leg alignment in which the knees angle inward so that they touch or nearly touch when standing, while the ankles remain separated. It is the opposite of bowlegs (genu varum).
A mild degree of knock knee is a normal part of growth in many children, typically most noticeable between about three and five years of age, and it usually corrects on its own as the child grows. In older children and adults, or when it is severe, one-sided, or painful, genu valgum may point to an underlying bone, growth, or metabolic problem that deserves evaluation.
Symptoms
For many children, the main feature is simply the appearance of the legs, with no discomfort. When symptoms do occur, they may include:
- Knees that touch while the ankles stay apart when standing with feet together
- An awkward or rolling gait, sometimes with the feet turning out
- Knee or hip pain, more common in adolescents and adults
- Pain or discomfort after walking or running
- Uneven shoe wear
- In one-sided cases, a noticeable difference between the two legs
Severe or persistent knock knees can place extra stress on the outer part of the knee and contribute to discomfort over time.
Causes
In young children, knock knees are most often a normal developmental stage. Other causes include:
- Growth variation: Normal swing from bowlegs in toddlers to knock knees in preschoolers, then to straighter alignment.
- Vitamin D deficiency (rickets) or other metabolic bone disease: Soft, poorly mineralized bone that bends under weight.
- Injury to a growth plate: A fracture near the knee can cause uneven growth and angulation.
- Bone conditions: Skeletal dysplasias and other inherited bone disorders.
- Obesity: Extra weight can contribute to or worsen alignment problems.
- Arthritis: In adults, knee arthritis can gradually shift alignment inward.
Risk Factors
- Age between roughly 3 and 5 years (physiologic knock knees)
- Vitamin D or calcium deficiency
- Previous fracture near the knee involving a growth plate
- Obesity
- Inherited bone or growth disorders
- Knee osteoarthritis in adults
Diagnosis
A clinician evaluates the legs, growth pattern, and any symptoms.
- Physical exam: Measuring the gap between the ankles when the knees are together, watching the child or adult walk, and checking for one-sided differences.
- Growth and history review: Age, family history, diet, and any past injuries help separate normal development from a problem.
- X-rays: Standing leg X-rays measure the angle and look for rickets, old fractures, or bone disease, mainly when alignment is severe, one-sided, painful, or worsening.
- Blood tests: Vitamin D, calcium, and related tests if a metabolic cause is suspected.
Treatment
Most childhood knock knees need no treatment beyond reassurance and observation, as alignment usually straightens with growth.
- Watchful waiting: For typical, mild, symmetric knock knees in young children, the clinician monitors over time.
- Treating the cause: Correcting vitamin D or calcium deficiency, or managing an underlying bone disease, allows alignment to improve.
- Weight management: Reducing excess weight lowers stress on the knees.
- Exercise and physical therapy: Strengthening the hip, thigh, and core muscles can help with comfort and function, especially in adolescents and adults.
- Guided growth surgery: In growing children with severe or progressive cases, a small procedure can temporarily slow growth on one side of the growth plate to let the leg straighten naturally.
- Realignment surgery (osteotomy): In adults or after growth is complete, the bone may be cut and realigned for severe deformity.
Prevention
- Ensure adequate vitamin D and calcium through diet, sunlight, and supplements when advised
- Maintain a healthy weight to reduce stress on the knees
- Have growth-plate injuries near the knee assessed and followed properly
- Keep active to support strong bones and muscles
- Have severe, one-sided, or worsening alignment checked rather than ignored
When to See a Doctor
See a clinician if knock knees are severe, affect only one leg, are getting worse rather than better, persist beyond about age seven, or appear with pain, a limp, or short stature. In adults, new or worsening knock-knee alignment with knee pain should be evaluated, as it may reflect arthritis or another joint problem. Sudden deformity after an injury needs prompt assessment.
Frequently Asked Questions
Are knock knees normal in children?
Yes, a mild degree of knock knees is a normal stage of growth, most noticeable around ages three to five. It usually straightens on its own by about age seven without any treatment. Severe, one-sided, painful, or worsening cases should be checked by a clinician.
Can knock knees be corrected without surgery?
Often, yes. In children they commonly correct on their own with growth, and treating causes such as vitamin D deficiency helps. Weight management and strengthening exercises improve comfort. Surgery is reserved for severe, progressive, or symptomatic cases.
Do knock knees cause knee pain or arthritis?
Mild knock knees usually cause no problems. Severe or long-standing misalignment places extra load on the outer part of the knee and may contribute to pain and, over many years, to wear in some people. Correcting alignment when it is severe can reduce this stress.
When should knock knees be evaluated by a doctor?
Have them assessed if they are severe, affect only one leg, are getting worse, persist beyond about age seven, or come with pain, a limp, or unusually short stature. In adults, new or worsening knock-knee alignment with pain should also be checked.
References
- American Academy of Orthopaedic Surgeons (AAOS). Knock Knees (Genu Valgum).
- Nemours KidsHealth. Knock Knees.
- MedlinePlus, U.S. National Library of Medicine. Knock knees.
- Mayo Clinic. Rickets — Symptoms and causes.