Why Do My Knees Cave In When I Squat?

Over exaggerated knee valgus on right.

Have you ever watched yourself squat, lunge or land from a jump and noticed your knees drifting inward?

This movement is commonly referred to as knee valgus. A small amount of inward movement isn't necessarily a problem, but if your knees consistently collapse inward—particularly under load or when you become tired—it may indicate that your body isn't controlling the movement as effectively as it could.

Understanding why this happens can help you improve the way you move rather than simply trying to force your knees into a different position.

What Is Knee Valgus?

Knee valgus describes the knee moving inward relative to the hip, foot and intended line of movement.

But here's the important part: what happens at the knee isn't always caused by the knee itself.

Your knee sits between your hip and ankle. If you lack mobility, strength or control at either of these joints, your body may compensate by changing the position of your knee.

This is why, when I see someone's knees moving inward during a movement assessment, I don't just look at their knees. I look at how the whole movement chain is working.

Why Do My Knees Cave In?

There isn't one single cause. Everyone moves differently, but two areas are particularly worth assessing.

1. Hip Strength and Control

The muscles around your hips and glutes help control the position of your thigh during movements such as squatting, running, jumping and changing direction.

If these muscles aren't providing enough strength or control for the movement, your thigh may rotate and move inward, bringing your knee with it.

This can become more noticeable as movements become more demanding or when you become fatigued.

2. Ankle Mobility and Foot Control

Your ankles also play an important role.

When you squat, your ankle needs enough dorsiflexion—the ability of your shin to move forwards over your foot.

If this movement is restricted, perhaps because of stiffness around the ankle or calf, your body may find another way to achieve the movement.

For some people, this can involve the foot rolling further inward, which can influence the position of the shin and knee above it.

Again, this doesn't mean everyone whose knees move inward has stiff ankles. The reason needs to be assessed rather than assumed.

Does Knee Valgus Affect Exercise and Sport?

Potentially.

Good movement isn't about making your body look perfectly symmetrical. It's about having the mobility, strength and control needed for the task you're asking it to perform.

Poorly controlled or excessive inward knee movement may affect how efficiently you produce and absorb force.

During a squat or jump, for example, better control through the hip, knee and ankle can help you transfer force effectively.

When running, landing or changing direction, having the strength and control to manage your knee position becomes even more important because the forces involved are considerably higher.

This is particularly relevant in sports involving running, jumping, cutting and rapid changes of direction.

What Injuries Can Be Associated With Knee Valgus?

Knee valgus doesn't automatically mean you are injured or that you will develop an injury. Pain and injury are usually multifactorial, meaning several factors—including training load, previous injury, strength, fatigue and movement control—can contribute.

However, excessive or poorly controlled knee valgus can increase the mechanical demands placed on different structures throughout the lower body and may be associated with several common problems.

These can include:

• Patellofemoral pain (often called runner's knee) – pain around or behind the kneecap. Changes in hip and knee mechanics can influence the forces acting around the patellofemoral joint.

  
  

• ACL strains and tears – poorly controlled knee valgus during high-force landing, cutting or rapid changes of direction can form part of a movement pattern that increases loading on the anterior cruciate ligament (ACL). Valgus alone doesn't cause an ACL injury, but controlling this position can be particularly important in sports involving jumping and direction changes.

  
  

• MCL strains – excessive inward movement of the knee can increase stress on structures along the inside of the knee, including the medial collateral ligament (MCL).

  
  

• Meniscus irritation or injury – poorly controlled rotation through the hip, knee and lower leg may contribute to increased stress through the knee during loaded twisting and turning movements.

  
  

• Patellar tendon pain – altered lower-limb mechanics may influence how forces are distributed through the knee and patellar tendon during repetitive jumping, running and squatting.

  
  

• IT band-related lateral knee pain – hip and lower-limb mechanics can influence loading around the outside of the knee, particularly during repetitive activities such as running.

  
  

• Hip and lower-limb overload – because the body works as a connected system, reduced control at the knee may occur alongside altered loading elsewhere in the hip, ankle and foot.

  
  

The important point is that seeing your knee move inward doesn't mean an injury is inevitable.

Instead, it can be a useful movement observation. If the movement is excessive, difficult to control, associated with pain or becomes more pronounced under load or fatigue, it may be worth investigating why it's happening.

How Can You Improve Knee Valgus?

There isn't one exercise or universal solution for knee valgus. The first step is understanding why your knees are moving inward and identifying the mobility, strength or movement-control factors contributing to it.

From there, we can work through a structured process to improve the way your lower body moves.

Step 1: Improve Restricted Mobility

If restrictions around your ankles, hips or surrounding muscles are contributing to your knee position, the first step is to improve the movement available at these areas.

For example, if your ankle cannot move forwards sufficiently during a squat, your body may compensate by allowing the foot to roll inward, which can influence the position of the shin and knee above it.

Rather than simply stretching everything, the aim is to identify where movement is genuinely restricted and address those specific areas.

This can involve two stages:

Release: Targeted pressure can be applied to specific muscles that are identified as overactive or restricted, helping to temporarily reduce muscle tension and improve the movement available.

Lengthen: This can then be followed with targeted stretching and mobility work to improve flexibility and range of motion around the restricted joint.

Together, these techniques aim to give your body the mobility it needs to perform the movement with fewer compensations.

Step 2: Improve Strength and Control

Once sufficient mobility is available, the next step is developing the strength and control needed to manage that movement.

This isn't simply about making your legs stronger or working muscles to exhaustion. The initial focus may be on targeting specific muscles that aren't contributing effectively to the movement.

For example, this could involve muscles around the hip that help control the position of the thigh, or muscles around the ankle and foot that contribute to lower-limb stability.

Through controlled, targeted movements, we can improve your ability to recruit these muscles and maintain better control of the hip, knee, ankle and foot.

The aim is to build the foundations needed to control your lower limb while producing and absorbing force.

Step 3: Retrain the Movement

Improving mobility and strengthening individual muscles is only part of the process.

The final step is teaching your body to use these improvements during whole-body movement.

This involves gradually integrating your improved mobility, strength and control into movement patterns, initially using slower and more controlled movements where good technique can be maintained.

As your control improves, the movements can gradually become more challenging, faster and more specific to the activities you need them for.

For everyday life and general exercise, this may mean maintaining good lower-body control during common movements and gym-based activities.

For athletes, progression may eventually include higher-speed running, jumping, landing and rapid changes of direction where the ability to control the lower limb becomes increasingly important.

The ultimate goal isn't to consciously think about your knee position every time you move. It's to develop the mobility, strength and movement control needed for better movement to become natural and automatic.

Don't Just Fix the Knee — Improve the Movement

If your knees move inward when you squat, the answer isn't necessarily to force them out.

Your body is a connected system.

Restrictions at your ankle, control at your foot, strength around your hip and the way your body coordinates movement can all influence what happens at your knee.

That's why I prefer to assess the movement first, identify what's contributing to it, and then work on the areas that actually need improving.

Because when we understand why your body moves the way it does, we can start building better movement from the ground up.

Move Better. Feel Great.