Knock Knees (Genu Valgum): Causes, Symptoms, Diagnosis, and Treatment

What is knock knee syndrome?

Knock knee syndrome, clinically known as genu valgum, is a common lower limb alignment where the knees angle inward and touch or nearly touch when a person stands with their feet apart.

Understanding Genu Valgum: The Basics

Genu valgum, commonly referred to as "knock knees," describes a condition in which the distal (lower) part of the leg deviates laterally (outward) relative to the knee joint, causing the knees to converge. While a mild degree of genu valgum is a normal developmental stage in toddlers (typically resolving by age 7-8), persistent or progressive knock knees in older children, adolescents, and adults can indicate underlying issues that warrant attention. This misalignment places abnormal stress on the knee joint and surrounding structures, potentially leading to pain, functional limitations, and long-term degenerative changes.

Anatomy and Biomechanics of Knock Knees

The human lower limb is designed to distribute forces efficiently through a complex interplay of bones, joints, muscles, and ligaments. In a healthy, neutral alignment, a straight line can be drawn from the center of the hip through the center of the knee and down to the center of the ankle. In genu valgum, this alignment is disrupted:

• Femoral Angle: The femur (thigh bone) often angles more acutely inward from the hip to the knee.
• Tibial Rotation: The tibia (shin bone) may exhibit external rotation relative to the femur.
• Joint Stress: The medial (inner) compartment of the knee bears increased compressive load, while the lateral (outer) compartment experiences increased tensile stress. This uneven distribution can accelerate wear and tear.
• Patellofemoral Mechanics: The kneecap (patella) may track improperly, often pulling laterally, leading to patellofemoral pain syndrome.
• Kinetic Chain Implications: Genu valgum is often part of a broader kinetic chain dysfunction. It can be associated with:
  • Hip Adduction and Internal Rotation: Weakness in the hip abductors (e.g., gluteus medius) and external rotators (e.g., gluteus maximus, piriformis) can allow the femur to adduct and internally rotate, contributing to knee valgus.
  • Foot Pronation: Excessive pronation (flattening) of the arch of the foot can cause internal rotation of the tibia, which can in turn contribute to knee valgus. This creates a "chain reaction" up the leg.

Common Causes and Risk Factors

Genu valgum can stem from a variety of factors, ranging from developmental to acquired conditions:

• Physiological Genu Valgum: Common in children aged 2-7 years as part of normal growth, usually self-correcting.
• Genetics: A family history of knock knees can increase predisposition.
• Rickets or Osteomalacia: Vitamin D deficiency leading to softening of bones, impairing proper bone development.
• Obesity: Excess body weight increases mechanical stress on the growth plates and joints, potentially exacerbating or causing valgus deformity, especially during critical growth periods.
• Trauma or Injury: Fractures or injuries to the growth plates around the knee in children can lead to asymmetrical growth.
• Infection: Bone infections (osteomyelitis) near the growth plates.
• Bone Dysplasias: Inherited disorders affecting bone and cartilage development.
• Muscle Imbalances:
  • Weakness: Insufficient strength in hip abductors (gluteus medius), hip external rotators, and vastus medialis obliquus (VMO) of the quadriceps.
  • Tightness: Overly tight hip adductors, tensor fascia latae (TFL), and hamstrings can pull the knee into a valgus position.
• Ligamentous Laxity: Hypermobility or looseness in the knee ligaments can contribute to instability and misalignment.

Recognizing the Symptoms

The primary symptom of knock knee syndrome is the visible inward angling of the knees. However, other symptoms can arise due to the altered biomechanics:

• Visual Alignment: Knees touching or nearly touching when standing with feet apart, often more noticeable when walking or running.
• Knee Pain: Often localized to the medial (inner) side of the knee due to increased compression, or around the kneecap (patellofemoral pain).
• Altered Gait: A "waddling" or "scissor" like gait as the knees may rub together during walking.
• Reduced Range of Motion: Difficulty fully extending or flexing the knee in some cases.
• Foot and Ankle Issues: Compensatory pronation of the feet, leading to arch pain or ankle discomfort.
• Hip Pain: Due to compensatory muscle activity or altered hip mechanics.
• Instability: A feeling of the knee "giving way," particularly during dynamic movements.

Diagnosis and Assessment

Diagnosis typically involves a combination of physical examination, gait analysis, and imaging:

• Physical Examination:
  • Visual Inspection: Observing the alignment of the legs from front, back, and side while standing.
  • Intermalleolar Distance (IMD): Measuring the distance between the medial malleoli (inner ankle bones) while the knees are touching. An IMD greater than 5-8 cm in adults is generally indicative of significant genu valgum.
  • Range of Motion (ROM): Assessing knee, hip, and ankle flexibility.
  • Muscle Strength Assessment: Identifying weaknesses in key muscle groups (e.g., hip abductors, VMO).
  • Palpation: Checking for tenderness around the knee joint.
• Gait Analysis: Observing walking and running patterns to identify compensatory movements and biomechanical inefficiencies.
• Imaging Studies:
  • X-rays: Full-length standing X-rays (mechanical axis views) are crucial to assess the precise degree of angular deformity and determine the mechanical axis of the limb, helping to guide treatment decisions.
  • MRI: May be used to assess soft tissue structures like cartilage, menisci, and ligaments if pain or other symptoms suggest internal damage.

Potential Complications and Long-Term Effects

If left unaddressed, persistent genu valgum can lead to several complications:

• Osteoarthritis: Increased load on the medial compartment of the knee significantly raises the risk of early-onset osteoarthritis.
• Patellofemoral Pain Syndrome (PFPS): Poor patellar tracking due to valgus alignment often leads to pain around and behind the kneecap.
• Meniscal Tears: The increased stress on the medial compartment can predispose to tears of the medial meniscus.
• Ligamentous Strain: Chronic strain on the medial collateral ligament (MCL) and other knee ligaments.
• Compensatory Problems: Issues can arise in other areas of the kinetic chain, including the hips (e.g., trochanteric bursitis) and ankles (e.g., plantar fasciitis).
• Functional Limitations: Difficulty with activities requiring knee stability, such as running, jumping, squatting, or prolonged standing.

Management and Treatment Approaches

Treatment for genu valgum depends on the underlying cause, severity, age of the individual, and presence of symptoms.

• Observation: For physiological genu valgum in young children, observation is often sufficient as the condition typically resolves with growth.
• Conservative Management:
  • Weight Management: For individuals with obesity, weight loss can significantly reduce stress on the knee joints.
  • Orthotics/Footwear: Custom or over-the-counter orthotics can help address excessive foot pronation, which may contribute to knee valgus.
  • Bracing: In some pediatric cases, night splints or braces may be used to guide bone growth.
  • Medication: Pain relievers (NSAIDs) can help manage pain and inflammation, but do not address the underlying alignment issue.
• Physical Therapy and Rehabilitation: The cornerstone of non-surgical management.
• Surgical Intervention: Reserved for severe cases, persistent pain, functional limitations, or progressive deformity, especially in adolescents nearing skeletal maturity or adults.
  • Guided Growth (Epiphysiodesis): In growing children, a small plate or screw can be temporarily placed on one side of the growth plate to slow growth on that side, allowing the other side to catch up and correct the deformity.
  • Osteotomy: In skeletally mature individuals, a wedge of bone is surgically removed or added to the femur or tibia to realign the limb and redistribute weight more evenly across the knee joint.

Exercise and Rehabilitation Strategies

A targeted exercise program is crucial for managing genu valgum by addressing muscle imbalances and improving biomechanics.

• Strengthening Exercises:
  • Hip Abductors: Clamshells, side-lying leg raises, banded walks (crab walks).
  • Hip External Rotators: Seated external rotations, standing hip external rotation with band.
  • Gluteus Maximus: Glute bridges, squats (with proper form, focusing on knee tracking), deadlifts.
  • Vastus Medialis Obliquus (VMO): Terminal knee extensions with resistance, leg press with focus on medial quad activation.
• Stretching Exercises:
  • Hip Adductors: Adductor stretch (butterfly stretch, seated straddle stretch).
  • Tensor Fascia Latae (TFL) and IT Band: IT band stretch, foam rolling.
  • Hamstrings and Calves: Standard hamstring and calf stretches.
• Neuromuscular Control and Balance:
  • Single-Leg Balance: Standing on one leg, progressing to unstable surfaces.
  • Proprioceptive Exercises: Wobble board, balance disc exercises.
  • Plyometrics (Advanced): Jumping and landing drills with emphasis on proper knee alignment.
• Gait Retraining: Consciously practicing walking with improved knee alignment and hip activation.
• Activity Modification: Avoiding or modifying activities that exacerbate pain or stress the knee in a valgus position, such as deep squats with valgus collapse.

Prevention and Lifestyle Considerations

While not all cases of genu valgum are preventable, certain measures can help minimize risk and progression:

• Maintain a Healthy Weight: Reducing excess load on the knee joints is paramount, especially during growth spurts.
• Nutritional Adequacy: Ensuring sufficient Vitamin D and calcium intake, particularly in children, to support healthy bone development.
• Proper Biomechanics: Learning and applying correct form during exercise, sports, and daily activities to avoid placing undue stress on the knees. This includes focusing on "knees over toes" or slight external rotation of the femur during squats and lunges.
• Early Intervention: Addressing muscle imbalances or gait abnormalities early can prevent progression of the deformity.

When to Seek Professional Help

It is advisable to consult a healthcare professional, such as an orthopedic specialist, physical therapist, or sports medicine physician, if you or your child experience:

• Persistent or Worsening Knee Pain: Especially if it interferes with daily activities or sleep.
• Progressive Deformity: If the knock-knee alignment appears to be worsening over time, particularly outside the typical developmental window.
• Functional Limitations: Difficulty walking, running, or participating in sports due to the alignment.
• Asymmetrical Knock Knees: If one knee is significantly more affected than the other.
• Underlying Medical Conditions: If there's a history of rickets, trauma, or other conditions that might contribute to the deformity.

Conclusion

Knock knee syndrome (genu valgum) is a common lower limb alignment issue that can range from a benign developmental phase in children to a painful and debilitating condition in adults. Understanding its causes, biomechanical implications, and potential long-term effects is crucial for effective management. Through a comprehensive approach involving exercise, targeted rehabilitation, and, in some cases, medical or surgical intervention, individuals with genu valgum can significantly improve their alignment, reduce pain, enhance function, and mitigate the risk of future complications. Early assessment and adherence to a tailored treatment plan are key to achieving the best possible outcomes.