Knee Valgus: Causes, Risks, and Corrective Strategies for Squats

Why do the knees go in during squats?

Knee valgus, or the inward collapse of the knees during a squat, is a common biomechanical fault often attributed to a complex interplay of muscular imbalances, mobility restrictions, and suboptimal motor control patterns.

Understanding Knee Valgus

Knee valgus, sometimes referred to as "knees caving in," describes a movement pattern where the knees track inward towards the midline of the body during the eccentric (lowering) or concentric (lifting) phases of a squat. This inward deviation is typically accompanied by hip adduction (the thigh moving inward) and internal rotation of the femur relative to the tibia. While a slight degree of knee valgus can be normal for some individuals, excessive or uncontrolled inward movement places undue stress on the knee joint and surrounding structures, increasing the risk of injury.

Primary Causes of Knee Valgus During Squats

The inward collapse of the knees during a squat is rarely due to a single factor but rather a combination of interconnected issues:

• Weak Gluteal Muscles:
  • Gluteus Medius and Minimus: These muscles are primary hip abductors and external rotators. When weak, they struggle to counteract the adduction and internal rotation forces that pull the knees inward, especially under load.
  • Gluteus Maximus: While primarily a hip extensor, the gluteus maximus also contributes to hip external rotation. Insufficient activation can lead to a lack of control over femoral rotation.
• Tight Adductor Muscles: The adductor group (e.g., adductor magnus, longus, brevis) pulls the thigh towards the midline. If these muscles are excessively tight, they can overpower the weaker gluteal muscles, actively pulling the knees inward during the squat.
• Limited Ankle Dorsiflexion: Insufficient range of motion in the ankle (inability to bring the shin forward over the foot) can severely impact squat mechanics. To compensate for limited ankle mobility and achieve adequate squat depth, the body will often shift weight forward, causing the knees to collapse inward to maintain balance and avoid falling backward.
• Poor Motor Control and Neuromuscular Coordination: Even with adequate strength and mobility, the brain's ability to effectively recruit and coordinate the correct muscles at the right time (neuromuscular control) may be lacking. This can lead to inefficient movement patterns where the body defaults to the path of least resistance, which often involves knee valgus.
• Improper Foot Placement or Arch Collapse:
  • Foot Placement: Feet positioned too narrow, too wide, or with an incorrect outward angle can predispose the knees to collapse.
  • Pronation (Flat Feet): Overpronation of the foot (where the arch collapses inward) can cause internal rotation of the tibia and femur, directly contributing to knee valgus.
• Insufficient Core Stability: A weak or disengaged core (abdominals, obliques, lower back muscles) can lead to a lack of proximal stability, forcing the distal joints (knees and ankles) to compensate and work harder, often resulting in suboptimal movement patterns like knee valgus.
• Load and Fatigue: When lifting heavy loads or performing high repetitions, pre-existing muscular imbalances or mobility restrictions become more pronounced. As fatigue sets in, the body's ability to maintain optimal form diminishes, making knee valgus more likely.
• Structural Factors: While less common as a primary cause, certain anatomical variations like a higher Q-angle (the angle formed by the quadriceps muscle from the hip to the kneecap) can predispose individuals to knee valgus.

The Risks of Persistent Knee Valgus

Ignoring persistent knee valgus can lead to a range of orthopedic issues due to the increased stress placed on the knee joint and surrounding tissues:

• Patellofemoral Pain Syndrome (Runner's Knee): Increased pressure and improper tracking of the kneecap.
• Medial Collateral Ligament (MCL) Strain: The MCL is stretched and stressed with repeated inward knee collapse.
• Meniscal Tears: Increased shear forces on the knee cartilage.
• Anterior Cruciate Ligament (ACL) Injury: While often associated with sudden, forceful movements, chronic knee valgus increases the risk of ACL tears over time due to repeated stress.
• IT Band Syndrome: Increased tension on the iliotibial band.

Correcting and Preventing Knee Valgus

Addressing knee valgus requires a systematic approach focusing on improving strength, mobility, and motor control.

• Strengthening Specific Muscles:
  • Gluteal Muscles: Incorporate exercises like glute bridges, clam shells, side-lying leg raises, banded lateral walks, monster walks, and single-leg RDLs. Focus on feeling the glutes activate.
  • Hip Abductors: Use resistance bands around the knees during squats (banded squats) to provide an external cue to push the knees out.
• Improving Mobility:
  • Ankle Dorsiflexion: Perform ankle mobility drills such as wall ankle mobilizations, kneeling ankle stretches, and banded ankle mobilizations.
  • Hip Adductor Flexibility: Incorporate stretches like the butterfly stretch, frog stretch, and wide-stance adductor stretches.
• Neuromuscular Re-education and Motor Control:
  • Conscious Cues: Actively "push your knees out" or "spread the floor with your feet" during squats.
  • Feedback: Use a mirror to monitor form or have a coach provide tactile cues (e.g., placing hands on your knees to guide outward movement).
  • Tempo and Pause Squats: Slowing down the movement or pausing at the bottom allows for greater awareness and control.
  • Box Squats: Can help reinforce proper depth and control.
• Proper Foot Mechanics:
  • "Tripod Foot": Learn to root your foot by distributing pressure evenly through the big toe, little toe, and heel, maintaining an active arch.
  • Footwear: Ensure your training shoes provide adequate support, or consider barefoot training (if appropriate for your facility and foot health) to improve foot intrinsic muscle strength.
• Progressive Overload and Load Management: Do not attempt to lift heavy loads until you can consistently maintain proper knee alignment with lighter weights. Gradually increase weight as form improves.
• Professional Guidance: Work with a qualified personal trainer, strength and conditioning coach, or physical therapist. They can perform a comprehensive movement assessment to identify the specific underlying causes of your knee valgus and prescribe a targeted corrective exercise program.

When to Seek Professional Help

If you experience persistent knee pain, notice a significant or worsening inward collapse of your knees during squats despite attempting corrective exercises, or if you have a history of knee injuries, it is highly recommended to consult with a healthcare professional such as a physical therapist, kinesiologist, or sports medicine physician. They can provide a definitive diagnosis, rule out structural issues, and guide you through a safe and effective rehabilitation plan.