Knee pain during a squat is a common experience that often signals an underlying issue with movement mechanics or tissue health. The squat is a complex, multi-joint movement engaging the ankles, knees, and hips; any misalignment in this chain can place undue stress on the knee joint. Discomfort is a signal that the body is moving inefficiently, potentially leading to long-term strain on cartilage, tendons, and ligaments. Understanding the specific cause of the pain is the first step toward correcting the issue and returning to pain-free movement.
Common Causes Related to Biomechanics
Many instances of knee pain during a squat stem from improper movement patterns or muscle imbalances that create faulty alignment. One of the most frequent errors is dynamic knee valgus, which is the inward collapse of the knees during the descent or ascent of the squat. This movement is often a direct result of weakness in the hip abductor muscles, particularly the gluteus medius. When the gluteus medius is insufficient, the femur internally rotates, pulling the knee inward and stressing the joint capsule and surrounding connective tissue.
Limited ankle dorsiflexion restricts the forward movement of the knee. This forces the body to compensate by either leaning excessively forward or allowing the knees to cave inward to achieve depth. This compensation shifts the weight distribution too far onto the balls of the feet and increases the shear force acting on the kneecap. Maintaining a neutral torso and pushing the hips backward helps distribute the load across the entire posterior chain, minimizing strain on the knee.
Poor weight distribution can also lead to pain, as placing the weight too far onto the toes forces the quadriceps to work harder and increases the compression load on the patellofemoral joint. Initiating a squat by bending the knees first, rather than pushing the hips back, also results in excessive forward knee travel. Tightness in the hip flexors or calves prevents the body from settling into a natural, deep squat position without compensatory movement at the knee.
Specific Structural Conditions
When biomechanical issues persist, they can lead to specific structural conditions within the knee joint, resulting in chronic or sharp pain. Patellofemoral Pain Syndrome (PFPS), commonly called “Runner’s Knee,” is characterized by a dull, aching, and diffuse pain felt around or behind the kneecap. This condition arises from the kneecap not tracking smoothly in its groove on the thigh bone, often due to muscle imbalances. The pain typically worsens with activities that require the knee to be bent under load, such as squatting, descending stairs, or sitting for long periods.
Patellar Tendinitis, or “Jumper’s Knee,” presents as sharp, localized pain just below the kneecap where the patellar tendon attaches to the shinbone. This overuse injury results from repetitive strain and excessive force on the tendon. The pain is usually aggravated by activities that store and release energy, such as jumping or explosive squatting. Sudden sharp pain during a squat may indicate a more acute issue like a meniscal tear or a severe ligament sprain.
Immediate Modifications and When to Stop
If knee pain occurs during a squat, immediate modifications must be made to reduce stress on the joint and allow the tissue to recover. A simple adjustment is to reduce the depth of the squat, moving only to the point just before the onset of pain. Temporary use of a box or chair squat can help limit depth and reinforce the movement pattern of sitting the hips back first. Experimenting with a slightly wider stance and pointing the toes outward can also help create more space in the hip joint, which may reduce the inward collapse of the knees.
For short-term relief, placing small weight plates or a thin wedge beneath the heels can temporarily improve ankle dorsiflexion, allowing the knees to track forward without excessive compensation. However, certain symptoms require immediate cessation of the exercise and prompt medical evaluation. Any sudden, sharp, or radiating pain, especially if accompanied by a locking, clicking, or grinding sensation, should halt the activity. Significant swelling, an inability to bear weight, or pain that persists for more than a few days despite rest are indications to seek consultation with a physical therapist or physician.
Long-Term Strategies for Strengthening and Mobility
Addressing the underlying causes of knee pain requires a focused, long-term approach that prioritizes targeted strengthening and mobility work. The hip abductors must be fortified to prevent knee valgus movement, using exercises like glute bridges, clamshells, and lateral walks with a resistance band. These movements specifically recruit the gluteus medius and minimus, restoring their ability to maintain proper alignment of the thigh bone during the squat. Developing strength in these stabilizers is necessary for preventing the knee from collapsing inward under load.
The quadriceps also require specific attention, particularly the Vastus Medialis Obliquus (VMO), the teardrop-shaped muscle on the inner thigh that helps ensure the kneecap tracks correctly. Low-load exercises such as terminal knee extensions or straight leg raises, often performed with the foot slightly turned out, are used to encourage VMO activation. Incorporating isometric hip adduction, such as squeezing a ball between the knees during a partial squat, can also facilitate VMO recruitment and improve quadriceps balance.
Mobility restrictions at the ankle and hip must also be resolved to allow for a biomechanically sound squat. Ankle dorsiflexion mobility can be improved through banded mobilization drills, where a resistance band pulls the ankle joint backward as the knee drives forward. Stretching the hip flexors and deep six external rotators improves the available range of motion at the hip, ensuring the body can descend into a low squat without compensating at the knee. Consistency with these low-load, high-repetition exercises is necessary for rehabilitating movement patterns and building long-term joint resilience.