Varus Knee: Understanding, Measurement, and Management

How do you measure your varus knee?

Measuring a varus knee, also known as genu varum or "bowlegs," typically involves a combination of visual assessment, goniometry for angular measurement, and most accurately, radiographic imaging to quantify the mechanical axis deviation and structural alignment of the lower limbs.

Understanding Varus Knee (Genu Varum)

A varus knee is a common lower limb alignment variation characterized by an outward bowing of the leg, causing the knees to remain apart when the ankles are together. From a biomechanical perspective, this means the mechanical axis of the lower limb (an imaginary line from the center of the hip to the center of the ankle) passes medial (inside) to the center of the knee joint.

Key characteristics include:

• Medial Compartment Loading: The varus alignment places increased compressive forces on the medial (inner) compartment of the knee, which can predispose individuals to medial meniscal tears and medial compartment osteoarthritis over time.
• Muscular Imbalances: Often associated with imbalances in the hip abductors/adductors and quadriceps/hamstrings, affecting gait and functional movement.
• Associated Conditions: Can be congenital, developmental (e.g., Blount's disease), or acquired due to trauma, arthritis, or metabolic bone diseases (e.g., rickets).

Understanding the degree of varus is crucial for assessing its potential impact on joint health, guiding intervention strategies, and monitoring progression.

Clinical Assessment of Varus Knee

Accurate measurement of varus knee alignment is best performed by a qualified healthcare professional, such as an orthopedic surgeon, physical therapist, or kinesiologist, using a combination of clinical examination and imaging techniques.

• Visual Inspection and Palpation:

  • Standing Posture: The clinician observes the patient in a relaxed standing position, facing forward, backward, and from the side. They look for the space between the knees when the ankles are touching, and the overall alignment of the lower limbs relative to the hips and ankles.
  • Gait Analysis: Observing the patient walk can reveal dynamic alignment issues, such as a "waddling" gait or increased medial thrust during the stance phase.
  • Patellar Tracking: Assessment of how the kneecap moves during knee flexion and extension can indicate associated rotational or muscular imbalances.

• Goniometry:

  • Goniometry is a clinical method used to measure the angles of joints. For the knee, it can quantify the tibiofemoral angle, which indicates the degree of varus or valgus.
  • Procedure:
    • The patient typically lies supine or stands.
    • The fulcrum of the goniometer is placed over the center of the knee joint (lateral epicondyle of the femur).
    • The stationary arm is aligned with the greater trochanter of the femur (or lateral midline of the thigh).
    • The movable arm is aligned with the lateral malleolus of the ankle (or lateral midline of the fibula).
    • The angle measured will indicate the deviation from a neutral 180-degree alignment (a normal tibiofemoral angle is typically 170-175 degrees of valgus, meaning a slight outward angle, so anything less than this or trending towards 180 degrees or beyond indicates varus).

• Radiographic Imaging (X-rays):

  • This is the most precise method for quantifying structural varus alignment, as it allows for direct visualization and measurement of bone angles and the mechanical axis.
  • Full-Length Standing Anteroposterior (AP) X-ray: Considered the gold standard. The patient stands with knees straight and weight-bearing, allowing the entire lower limb (hip to ankle) to be captured on a single image.
  • Mechanical Axis Deviation (MAD): On these X-rays, the mechanical axis (a line from the center of the femoral head to the center of the ankle) is drawn. The distance this line deviates from the center of the knee joint (specifically, the midpoint of the tibial spines) is measured. A medial deviation indicates varus. The greater the deviation, the more significant the varus.
  • Joint Line Convergence Angle (JLCA): This measures the angle between the femoral and tibial joint surfaces, providing insight into joint space narrowing, which is common in varus knees with osteoarthritis.
  • Magnetic Resonance Imaging (MRI): While not typically used for primary alignment measurement, MRI can provide detailed images of soft tissues (cartilage, meniscus, ligaments), which are often affected by chronic varus loading.

• 3D Motion Analysis:

  • In specialized research or clinical settings, 3D motion analysis systems (using reflective markers and infrared cameras) can provide highly detailed, dynamic measurements of lower limb kinematics and kinetics during activities like walking or running. This offers insights into how varus alignment impacts movement patterns and joint loading in real-time.

Self-Assessment and Home Observation

While self-assessment cannot replace a professional diagnosis, you can perform simple observations to note potential signs of varus knee.

• Stand Naturally: Stand upright with your feet together, heels touching, and pointing straight forward.
• Observe Your Knees:
  • Do your knees touch? In a varus alignment, there will be a noticeable gap between your knees even when your ankles are together.
  • Is there an outward bowing of your shins relative to your thighs?
• Mirror Test: Stand in front of a full-length mirror and observe your legs from the front and back.
• Gait Observation: Ask a trusted friend or family member to observe you walking from behind. Look for any outward thrust of the knees or a waddling gait.

Remember, these are observational cues only and should prompt a professional evaluation if you have concerns.

Why Accurate Measurement Matters

Precise measurement of varus knee alignment is critical for several reasons:

• Diagnosis and Severity: It confirms the presence of genu varum and quantifies its severity, which is essential for diagnosis.
• Prognosis: The degree of varus can help predict the likelihood of developing or progressing knee osteoarthritis.
• Treatment Planning: Measurement guides conservative interventions (e.g., specific exercises, bracing, orthotics) and informs surgical decisions (e.g., high tibial osteotomy to realign the limb, or knee replacement).
• Monitoring Progression: Serial measurements over time can track whether the deformity is stable, improving, or worsening, allowing for timely adjustments to treatment.
• Outcome Assessment: Post-intervention measurements help evaluate the success of treatment in correcting alignment.

When to Seek Professional Assessment

If you suspect you have a varus knee or experience any of the following symptoms, it is advisable to consult a healthcare professional:

• Persistent knee pain, especially on the inner side of the knee.
• Noticeable outward bowing of the legs.
• Difficulty with walking or running.
• Knee instability or "giving way."
• Changes in gait or posture.
• Concern about joint health or potential long-term complications.

Management and Intervention Strategies

Depending on the cause and severity of the varus knee, management strategies can range from conservative to surgical.

• Conservative Management:
  • Exercise and Physical Therapy: Strengthening hip abductors, gluteal muscles, and quadriceps, along with stretching tight adductors and hamstrings, can help improve muscular balance and dynamic stability.
  • Orthotics and Bracing: Custom shoe orthotics can help redistribute pressure, and knee braces may be used to provide support or correct alignment.
  • Activity Modification: Avoiding high-impact activities or prolonged standing that exacerbate symptoms.
• Surgical Intervention:
  • High Tibial Osteotomy (HTO): A common procedure for younger, active individuals with isolated medial compartment arthritis and varus alignment. A wedge of bone is removed or added to the tibia to shift the mechanical axis laterally, offloading the medial compartment.
  • Total Knee Arthroplasty (TKA): For severe varus deformity with widespread knee arthritis, knee replacement surgery may be necessary to restore proper alignment and joint function.

Understanding and accurately measuring varus knee alignment is fundamental to effective management and preserving long-term knee health.