What is a Hyperextended Knee?

Definition of Hyperextended Knee:

A hyperextended knee occurs when the knee joint is extended beyond its normal range of motion, causing an exaggerated straightening of the leg. This typically results from a rapid shift in weight or an abrupt change in direction while the foot is planted on the ground.

hyperextended knee posture

Anatomy Overview:

knee anatomy activ8 posture therapy

The main skeletal anatomy involves the femur (thigh bone), tibia and fibula (shin bones), and patella. A hyperextended knee’s anatomical position includes an excessive straightening of the knee joint — where the knee bends backward, extending past zero degrees of flexion.

The knee joint movements are primarily flexion and extension, which occur in the sagittal plane of motion (or front-to-back). With knee joint hyperextension, the joint plane of movement is straight back but may be accompanied by leg rotation and, more commonly, bow legs (or varus stress).

The boney landmarks observed in a postural assessment are primarily those seen in the side views, including the greater trochanter of the femur to approximate the hip joint, the center of the knee, and the lateral malleolus to approximate the ankle. Examination of these areas in relation to one another indicates the degree of knee hyperextension present. An X-ray is unnecessary to see excessive hyperextension.

Synonymous Posture Terms:

  • Genu recurvatum
  • Back knee

The Biomechanics of Hyperextended Knees

Skeletal and Muscular Structures:

The skeletal anatomy involved in a hyperextended knee includes the femur (the thigh bone), tibia (the larger bone in the lower leg), fibula (the smaller bone in the lower leg), and patella (the knee cap). These bones form the complex joint structure of the knee, which is pivotal for weight-bearing and locomotion.

Hyperextended knee refers to the excessive straightening of the knee joint. Under normal conditions, the knee joint allows for flexion and extension within a specific range (normally 0 degrees, or straight, to 135 degrees of flexion). However, this range is surpassed in a hyperextended knee, leading to an over-straightened or overstretched knee position - sometimes occurring in normal activities versus only in sports injuries. This is not a natural or healthy state for the knee and often results from a sudden force or trauma to the knee while the foot is firmly planted on the ground.

Joint Movements

As the term suggests, hyperextension is the primary joint movement involved in a hyperextended knee. In this condition, the knee joint is forced to move beyond its normal range of extension, pushing the tibia (shinbone) forward in relation to the femur (thighbone). This unnatural movement can lead to strain or injury to the ligaments and other soft tissues supporting the knee joint.

This exaggerated movement occurs in the sagittal plane, a vertical plane that divides the body into left and right sides. In sports medicine, we see this when most of our body's forward and backward movements, such as walking or running, occur in this plane. In the case of a hyperextended knee, the lower leg's excessive backward movement (extension) happens in the sagittal plane.

Certain boney landmarks and musculature exhibit noticeable strain and tension in a hyperextended knee. There is an anterior translation of the tibia relative to the femur, which means the shinbone is pushed forward in relation to the thighbone. This results in significant strain on the posterior cruciate ligament (PCL), a key ligament that stabilizes the knee joint. Additionally, there can also be a potential strain on the popliteal tendon, a structure located at the back of the knee, further compromising the stability and function of the knee.

Muscularly, the quadriceps muscles in the front of the thigh may be overly dominant or tight, overpowering the hamstrings in the back of the thigh, leading to this excessive straightening. It’s important not to overlook the myofascial lines running up and down the front of the knee and back that involve the flexion and extension of the knees when resolving this issue.

Postural Deviations Found with Hyperextended Knees:

Accompanying posture deviations commonly include:

What are the Symptoms of a Hyperextended Knee?

pain symptoms from knee hyperextension

Common Pains and Limitations:

Due to the muscle imbalances at the hips, knees, ankles, and feet, the following symptoms and common injuries occur:

  • Knee injury and knee pain
  • Hip injury and hip pain
  • Ankle sprain and pain
  • Instability in the knee, hip, and ankle
  • Decreased range of motion at the hips, pelvis, and ankles to compensate
  • Difficulty walking or running
  • General hyperlaxity or hypermobility

Long-Term Risks and Issues:

  • Damage to the cartilage or menisci of the knee
  • Chronic knee instability
  • Knee ligament injuries
    • ACL injury (Anterior Cruciate Ligament)
    • PCL injury (Posterior Cruciate Ligament)
    • MCL injury (Medial Collateral Ligament)
    • LCL injury (Lateral Collateral Ligament)
  • Meniscus tear
  • Hip labral tear
  • Osteoarthritis
  • Low back pain

What Causes Hyperextended Knees?

signs of joint hypermobility syndrome ehlers danlos

Hyperextended knees have a variety of causes, from sudden traumatic injuries to underlying physical conditions that predispose individuals to such an issue. Sports activities and accidents are common causes of knee hyperextension injuries, especially in situations where a strong force is applied to the knee while the foot is planted on the ground. Rapid changes in direction, sudden stops, or even a hard fall can cause the knee to hyperextend, potentially leading to injuries of the ligaments or other structures within the knee.

Women, interestingly, tend to experience severe cases of hyperextended knees more frequently than men. This could be due to the general differences in joint laxity and flexibility between the sexes, with women typically having more flexibility but less stability. The higher prevalence in women may also be connected to hormonal factors, as certain hormones can influence ligament laxity.

Furthermore, hyperextension of the knees is more common in individuals with ligamentous or fascial laxity. Ligamentous laxity refers to unusually loose ligaments, which can result in hypermobile joints (including more severe cases with joint hypermobility syndrome and Ehlers-Danlos syndrome). This can predispose a person to a hyperextended knee injury, as the knee joint may not be as stable as it needs to be to prevent excessive movement. Fascial laxity refers to looseness in the fascia, the connective tissue that encloses the muscles and organs. When the fascia surrounding the muscles that support the knee is lax, it can contribute to conditions like hyperextended knees.

hyperextended knees with poor posture

Muscle imbalances and poor posture play a crucial role

Muscle imbalances also play a significant role in causing hyperextended knees. If the muscles on one side of a joint are stronger or more flexible than the other, the joint can move beyond its normal range. For instance, if the quadriceps (front thigh muscles) are significantly stronger than the hamstrings (back thigh muscles), they can pull the knee into hyperextension. Similarly, tight hip flexors and weak glutes can contribute to this condition.

Improper exercise techniques or biomechanics can lead to hyperextended knees too. For example, locking out the knees during a leg press or squat can strain the knee joint excessively, causing it to hyperextend. Unfortunately, most athletes opt for a knee brace or compression wraps to help after they get an injured knee versus using preventive measures.

It's important to note that while some individuals may have a natural tendency towards slight hyperextension without pain or major functional issues, significant hyperextension or hyperextension accompanied by pain should be assessed and managed by a healthcare provider to prevent further injury or long-term knee problems.

Posture Terms Related to Hyperextended Knees

  • Knee Flexion: The opposite motion of knee extension, bending the knee.
  • Bow Legs: A condition where the knees angle outward, away from each other.
  • Knee Internal Rotation: This commonly is found with hyperextended knees when instability is present.
  • Anterior Pelvic Tilt: With the femur moving posteriorly into extension, the pelvis often tilts anterior.


In conclusion, hyperextended knees can be a significant source of discomfort and may lead to long-term health complications if not addressed properly. Understanding the causes and potential treatments is crucial to navigating this condition effectively.

One effective approach to managing and potentially avoiding the issue of hyperextended knees lies in the practice of posture therapy. This holistic approach not only focuses on the symptoms but also seeks to correct the underlying imbalances that contribute to your discomfort. By incorporating personalized exercise therapy routines, it promotes strength, flexibility, and most importantly, balance among the body's musculoskeletal system, providing a comprehensive solution.

If you are experiencing knee discomfort, or if you've been told that you have a hyperextended knee, remember that help is available. You don't have to live with the discomfort or limitations that this condition might be causing you.

Invest in your well-being today. Your first step towards a healthier, more balanced body could be as simple as reaching out to us to inquire more about posture therapy. Remember, your body is your most valuable asset. Taking care of it is not just an option, it's a necessity.

Posture therapy could be your key to unlocking a more comfortable, flexible, and healthier you. Reach out to us today, and let's get started on the journey to a better body balance together. Your future self will thank you.

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