Knee Pain During Squats: Causes, Biomechanics, and Corrective Strategies

Why Does My Knee Hurt When I Squat?

Knee pain during squats is a common complaint among lifters and athletes, often stemming from a complex interplay of biomechanical faults, muscle imbalances, inadequate mobility, or improper loading strategies, rather than a single cause.

The squat is a fundamental human movement and a cornerstone of strength training, engaging a vast network of muscles including the quadriceps, hamstrings, glutes, and core. When performed correctly, it’s highly beneficial for strength, power, and overall functional fitness. However, due to the significant forces placed on the knee joint, improper technique or underlying anatomical issues can lead to pain. Understanding the potential causes is the first step toward effective resolution.

Understanding the Knee Joint and Squat Biomechanics

The knee is a complex hinge joint primarily responsible for flexion and extension, with some rotational capacity. It comprises the articulation of the femur (thigh bone), tibia (shin bone), and patella (kneecap). Key structures include:

• Menisci: C-shaped cartilage pads that cushion the joint and aid in stability.
• Ligaments: Provide stability (e.g., ACL, PCL, MCL, LCL).
• Articular Cartilage: Covers the ends of the bones, allowing smooth movement.
• Tendons: Connect muscles to bones (e.g., patellar tendon, quadriceps tendon).

Optimal Squat Biomechanics: A well-executed squat involves a coordinated movement pattern:

• Hip Hinge: Initiating the movement by pushing the hips back.
• Knee Tracking: Knees should generally track in line with the toes, avoiding excessive caving inward (valgus collapse) or bowing outward (varus collapse).
• Controlled Descent: Maintaining tension and control throughout the movement.
• Balanced Muscle Activation: Engaging glutes, quads, and hamstrings synergistically.
• Appropriate Depth: Squatting to a depth that allows for good form without pain or compensation.

Common Causes of Knee Pain During Squats

Knee pain during squats can arise from various tissues and mechanical issues.

• Patellofemoral Pain Syndrome (PFPS):

  • Often referred to as "runner's knee," this is the most common cause of anterior (front) knee pain. It results from irritation of the cartilage beneath the kneecap, often due to improper tracking of the patella in its groove on the femur.
  • Contributing Factors: Weakness in the vastus medialis obliquus (VMO) of the quadriceps, tight IT band, tight hamstrings/quads, gluteal weakness (especially glute medius), or foot overpronation.
  • Symptoms: Dull ache around or behind the kneecap, pain worse with bending the knee, ascending/descending stairs, or prolonged sitting.

• Tendinopathy (Patellar or Quadriceps Tendon):

  • Inflammation or degeneration of the patellar tendon (below the kneecap) or quadriceps tendon (above the kneecap). Often called "jumper's knee" for patellar tendinopathy.
  • Contributing Factors: Overuse, sudden increase in training volume or intensity, repetitive high-impact activities, or poor landing mechanics.
  • Symptoms: Localized pain and tenderness directly on the affected tendon, especially during or after activity, stiffness.

• Meniscus Injury:

  • Tears or degeneration of the menisci, the cartilage cushions in the knee.
  • Contributing Factors: Deep squats with heavy loads, especially if combined with twisting motions, or acute trauma. Degenerative tears can occur over time.
  • Symptoms: Sharp pain, clicking, popping, catching, or locking sensation in the knee, swelling, tenderness along the joint line.

• Ligamentous Strain (e.g., MCL, LCL):

  • Though less common as a primary cause of squat pain unless there's significant valgus/varus collapse or a history of injury, a strain to the Medial Collateral Ligament (MCL) or Lateral Collateral Ligament (LCL) can be exacerbated by squatting.
  • Contributing Factors: Excessive knee valgus (knees caving in) during a squat, placing stress on the MCL.
  • Symptoms: Pain on the inside (MCL) or outside (LCL) of the knee, tenderness, potential instability.

• Osteoarthritis (OA):

  • Degenerative joint disease where the cartilage wears down over time.
  • Contributing Factors: Age, previous injury, chronic joint stress, genetics.
  • Symptoms: Deep, aching pain, stiffness (especially in the morning), grinding or creaking sensations (crepitus), reduced range of motion.

Biomechanical Contributors and Form Faults

Beyond specific tissue pathologies, several form errors and biomechanical imbalances can directly lead to knee pain during squats.

• Knees Caving In (Valgus Collapse):

  • This is one of the most common and problematic squat faults. When the knees collapse inward, it places excessive stress on the medial aspect of the knee joint (MCL) and alters patellar tracking.
  • Causes: Weakness in the gluteus medius and maximus, tight adductors, poor motor control, or flat feet/overpronation.

• Excessive Forward Knee Travel:

  • While "knees past toes" is not inherently bad for everyone, especially those with good ankle mobility and balanced strength, excessive forward knee travel without a corresponding hip hinge can significantly increase shear forces on the knee joint and patellar tendon.
  • Causes: Limited ankle dorsiflexion, weak glutes/hamstrings (leading to quad dominance), or a lack of understanding of hip hinge mechanics.

• Insufficient Squat Depth:

  • Not squatting deep enough can lead to excessive loading on the quads without fully engaging the glutes and hamstrings, potentially leading to quad dominance and patellofemoral stress. Conversely, squatting too deep for one's mobility can also be problematic.

• Poor Foot Placement and Arch Collapse:

  • Feet too narrow, too wide, or excessive arch collapse (pronation) can disrupt the kinetic chain, leading to altered knee tracking and increased stress.

• Lack of Hip Hinge:

  • Failing to initiate the squat with a hip hinge and instead dropping straight down into knee flexion puts disproportionate stress on the knees rather than distributing the load across the hips and glutes.

• Overloading Too Soon / Rapid Progression:

  • Increasing weight or volume too quickly without allowing the body to adapt is a primary cause of overuse injuries like tendinopathy.

Corrective Strategies and Prevention

Addressing squat-related knee pain requires a multi-faceted approach, focusing on form, strength, and mobility.

• Mastering Squat Form:

  • Cueing: Focus on cues like "knees out," "screw your feet into the floor," "sit back into your hips," and "chest up."
  • Video Analysis: Record your squats from the front and side to identify form faults.
  • Box Squats: Can help teach proper hip hinge and depth control.
  • Goblet Squats: Often easier to learn proper mechanics due to the front load.

• Targeted Strengthening:

  • Glutes: Strengthen the gluteus medius and maximus to improve hip stability and prevent valgus collapse. Exercises include glute bridges, banded walks (sideways, monster walks), clam shells, and single-leg RDLs.
  • Vastus Medialis Obliquus (VMO): Focus on exercises that target the inner quad, such as terminal knee extensions or leg extensions with a focus on the last few degrees of extension.
  • Hamstrings and Adductors: Ensure balanced strength to support the knee joint. Romanian Deadlifts (RDLs), Good Mornings, and Copenhagen planks are beneficial.
  • Core Strength: A strong core provides a stable base for movement, improving overall biomechanics.

• Improving Mobility:

  • Ankle Dorsiflexion: Limited ankle mobility often forces the knees excessively forward. Perform ankle mobility drills like wall ankle stretches or banded ankle mobilizations.
  • Hip Mobility: Tight hip flexors or adductors can restrict proper hip hinge and external rotation. Incorporate hip flexor stretches, 90/90 stretches, and dynamic hip mobility drills.
  • Thoracic Spine Mobility: A stiff upper back can affect overall posture and ability to maintain an upright torso, indirectly impacting squat form.

• Load Management:

  • Start Light: Prioritize perfect form with light weights or even just bodyweight before adding significant load.
  • Progressive Overload: Increase weight, reps, or sets gradually. Avoid sudden jumps in intensity or volume.
  • Vary Squat Variations: Incorporate different squat types (front squats, pause squats, tempo squats) to challenge your body in varied ways and identify weaknesses.

• Warm-up and Cool-down:

  • Dynamic Warm-up: Prepare your muscles and joints with movements like leg swings, hip circles, and bodyweight squats.
  • Static Cool-down: Stretch major muscle groups involved in squatting after your workout.

• Appropriate Footwear: Wear stable, flat-soled shoes that provide a good base of support, or consider weightlifting shoes if appropriate for your training goals.

When to Seek Professional Help

While many cases of squat-related knee pain can be resolved with self-correction and diligent training, it's crucial to know when to consult a healthcare professional. Seek expert advice if you experience:

• Persistent pain that doesn't improve with rest, form correction, or strengthening.
• Sharp, sudden pain during or after a squat.
• Significant swelling, redness, or warmth around the knee joint.
• Locking, catching, or giving way of the knee.
• Pain that limits daily activities outside of exercise.

A physiotherapist, sports medicine doctor, or orthopedic specialist can accurately diagnose the underlying cause of your knee pain and provide a tailored treatment plan, which may include manual therapy, specific exercises, or in rare cases, medical intervention.