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

What is a knock knees deformity also known as?

A knock knees deformity is medically and scientifically known as Genu Valgum. It is a common lower limb alignment variation characterized by the knees angling inward and touching or almost touching when the individual stands with their feet together, leaving a noticeable gap between the ankles.

What is Genu Valgum (Knock Knees)?

Genu valgum, more commonly known as "knock knees," describes a condition where the knees deviate medially (inward) towards the midline of the body. In a healthy, neutral alignment, a straight line can be drawn from the hip joint through the center of the knee to the ankle. In genu valgum, this line is disrupted, with the knee falling inside this imaginary line. The term "valgus" in "genu valgum" refers to the distal segment (in this case, the lower leg or tibia) being angled away from the midline of the body, creating an "L" shape at the knee joint.

Anatomy and Biomechanics of Genu Valgum

Understanding the anatomy and biomechanics involved is crucial for appreciating the implications of genu valgum. The condition primarily affects the tibiofemoral joint (the knee joint, formed by the femur and tibia).

• Bony Alignment: In genu valgum, the distal end of the femur and the proximal end of the tibia are angled such that the knee joint is more medially positioned than the hip and ankle joints. This places increased stress on the lateral (outer) compartment of the knee and often stretches the medial collateral ligament (MCL).
• Muscle Imbalances: Genu valgum is frequently associated with specific muscle imbalances throughout the kinetic chain:
  • Weakness: Often observed in the hip abductors (e.g., gluteus medius, gluteus minimus) and external rotators, leading to increased hip adduction and internal rotation. The vastus medialis obliquus (VMO), a part of the quadriceps, may also be weak or inhibited, contributing to poor patellar tracking.
  • Tightness: Common in the hip adductors (e.g., adductor magnus, longus, brevis) and tensor fascia latae/iliotibial band (ITB), pulling the knee inward.
• Kinetic Chain Implications: Genu valgum is rarely an isolated knee issue. It often has implications both above and below the knee:
  • Foot and Ankle: Compensatory excessive pronation of the foot (flattening of the arch) is common, as the body attempts to absorb the inward rotation from the knee.
  • Hip: Increased hip adduction and internal rotation.
  • Spine: Can sometimes contribute to altered pelvic tilt and lower back pain due to compensatory movements.

Common Causes of Knock Knees

The causes of genu valgum can vary from benign developmental stages to more serious underlying conditions.

• Physiological Genu Valgum: This is the most common type, typically observed in children between the ages of 2 and 6 years. It is a normal part of development and usually corrects itself as the child grows and their bones mature.
• Pathological Genu Valgum: This refers to knock knees that persist beyond childhood, are severe, or develop due to an underlying medical condition.
  • Genetic Predisposition: A family history of knock knees.
  • Metabolic Bone Diseases: Conditions like rickets (vitamin D deficiency) or osteomalacia can weaken bones and lead to deformities.
  • Trauma or Infection: Injury to the growth plates (epiphyseal plates) in children can disrupt normal bone growth.
  • Obesity: Excessive body weight places increased stress on the knees, potentially exacerbating or causing genu valgum.
  • Ligamentous Laxity: General joint hypermobility or loose ligaments around the knee can contribute to instability and valgus alignment.
  • Compensatory Mechanisms: Sometimes, genu valgum can develop as a compensatory response to other issues, such as excessive foot pronation or hip internal rotation.
  • Rheumatoid Arthritis or Osteoarthritis: Degenerative joint diseases can lead to cartilage loss and bone changes that contribute to deformity.

Symptoms and Associated Problems

While some individuals with mild genu valgum may be asymptomatic, more pronounced cases can lead to various symptoms and complications:

• Visible Deformity: The most obvious symptom is the inward angling of the knees, which may become more apparent during standing or walking.
• Pain: Pain is common, particularly on the medial (inner) side of the knee due to stretching of the MCL and increased stress on the lateral compartment, which can lead to cartilage wear. Pain may also radiate to the hips, ankles, or lower back due to altered biomechanics.
• Altered Gait: Individuals may develop an "in-toeing" or "waddling" gait as they attempt to compensate for the inward knee alignment.
• Increased Risk of Injury:
  • Patellofemoral Pain Syndrome: Misalignment can lead to improper tracking of the kneecap, causing pain around the patella.
  • Ligamentous Strain: Chronic stress on the medial collateral ligament (MCL).
  • Meniscal Tears: Increased compression on the lateral meniscus.
  • Osteoarthritis: Long-term abnormal loading can accelerate wear and tear of the articular cartilage, particularly in the lateral compartment.
• Reduced Athletic Performance: Impaired running mechanics, jumping, and cutting movements.

Diagnosis of Genu Valgum

Diagnosis typically involves a combination of physical examination, medical history, and sometimes imaging studies.

• Physical Examination:
  • Visual Assessment: Observing the alignment of the lower limbs while standing, walking, and performing functional movements.
  • Goniometry: Measuring the Q-angle (quadriceps angle), which reflects the angle between the quadriceps muscle and the patellar tendon, providing insight into patellar tracking and knee alignment.
  • Palpation: Checking for tenderness, swelling, or muscle imbalances.
  • Range of Motion: Assessing joint flexibility and mobility.
• Gait Analysis: Observing the walking pattern to identify compensatory movements and biomechanical inefficiencies.
• Medical History: Inquiring about onset, progression, pain, past injuries, family history, and any underlying medical conditions.
• Imaging:
  • X-rays: Standing weight-bearing X-rays of the lower limbs are crucial to assess the true bony alignment and measure angles like the femorotibial angle.
  • MRI (Magnetic Resonance Imaging): May be used to assess soft tissue structures (ligaments, menisci, cartilage) if pain or other symptoms suggest internal knee damage.

Management and Treatment Approaches

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

• Non-Surgical Management:
  • Observation: For physiological genu valgum in young children, often no intervention is needed as it typically self-corrects.
  • Physical Therapy: A cornerstone of treatment for many cases. Focuses on:
    • Strengthening: Targeting weak muscles like hip abductors, external rotators, gluteus maximus, and vastus medialis obliquus (VMO).
    • Stretching: Addressing tight muscles such as hip adductors, hamstrings, and the IT band.
    • Proprioception and Balance Training: Improving neuromuscular control and stability.
    • Gait Retraining: Correcting dysfunctional walking patterns.
  • Orthotics and Bracing:
    • Shoe Inserts (Orthotics): Custom or off-the-shelf orthotics can help support the arch of the foot if excessive pronation is contributing to the valgus alignment.
    • Knee Braces: In some cases, specific knee braces may be used to provide support and encourage better alignment, especially during activities.
  • Weight Management: For individuals who are overweight or obese, weight loss can significantly reduce stress on the knee joints.
  • Pain Management: Over-the-counter pain relievers (NSAIDs), ice, and rest may be recommended for symptomatic relief.
• Surgical Management:
  • Surgery is typically reserved for severe cases, those that cause significant pain or functional limitations, or when non-surgical options have failed.
  • Osteotomy: A surgical procedure where a wedge of bone is either removed or added to the femur or tibia to realign the limb and correct the angle.
  • Guided Growth Surgery (Epiphysiodesis): For children with significant genu valgum and remaining growth potential, small plates or screws can be placed on one side of the growth plate to temporarily slow growth on that side, allowing the other side to catch up and correct the deformity over time.

Exercise Considerations and Corrective Strategies

For individuals with genu valgum, a targeted exercise program, ideally under the guidance of a physical therapist or knowledgeable trainer, can help improve alignment, strength, and reduce symptoms.

• Strengthening Exercises:
  • Hip Abductors: Clamshells, side-lying leg raises, banded walks (sideways, forward/backward).
  • Gluteus Medius and Maximus: Glute bridges, single-leg Romanian deadlifts (RDLs), squats (with emphasis on knee tracking).
  • Vastus Medialis Obliquus (VMO): Terminal knee extensions with a resistance band, leg presses with internal rotation emphasis.
  • Core Stabilizers: Planks, bird-dog, dead bug to improve trunk stability, which influences lower limb mechanics.
• Stretching and Mobility Exercises:
  • Hip Adductors: Butterfly stretch, wide-stance forward fold, standing adductor stretch.
  • Iliotibial Band (ITB): IT band stretch (crossing one leg behind the other and leaning away).
  • Ankle Mobility: Calf stretches (gastrocnemius and soleus) if ankle pronation is present.
• Neuromuscular Control and Form Correction:
  • Squat and Lunge Variations: Practice these movements in front of a mirror, focusing on keeping the knees tracking directly over the second or third toe, avoiding inward collapse. Use resistance bands around the knees to provide external cueing for knee abduction.
  • Single-Leg Balance: Standing on one leg to improve proprioception and strengthen stabilizing muscles.
• Footwear: Wear supportive shoes and consider custom orthotics if excessive foot pronation is a contributing factor.

When to Seek Professional Medical Advice

While mild genu valgum may not require intervention, it's important to seek professional medical advice if you experience any of the following:

• Persistent or Worsening Pain: Especially if it affects daily activities or exercise.
• Progressive Deformity: If the knock-knee appearance becomes more pronounced over time, particularly in children.
• Unilateral Knock Knees: If only one knee is affected, as this can indicate an underlying issue like trauma, infection, or a growth plate disturbance.
• Significant Impact on Function: Difficulty walking, running, or participating in sports due to pain or instability.
• Associated Symptoms: Such as a limp, joint swelling, or locking/clicking in the knee.

Conclusion

Genu valgum, or knock knees, is a common lower limb alignment variation that can range from a normal developmental phase in children to a pathological condition requiring intervention. Understanding its underlying causes, anatomical implications, and biomechanical consequences is essential. While physiological cases often resolve spontaneously, persistent or symptomatic genu valgum can lead to pain, functional limitations, and an increased risk of long-term joint issues. A comprehensive approach involving physical therapy, targeted exercises, and sometimes orthotics or surgical correction, guided by an expert, can effectively manage the condition and improve quality of life.