The Most Common Causes of Knee Pain

The knee bears significant importance in an individual's ability to move freely. The slightest injury could result in pain and discomfort.  More significant knee damage might precipitate mobility issues that might interfere with a stricken person's mobility and lifestyle. Studies compiled by the Centers For Disease Control (CDC) have concluded that many Americans, ranging in age, suffer from knee pain and that such discomfort has increased in incidents by significant percentages over the last two decades.

Let's examine the knee, the bodily structure's important working components, the types of injuries and illnesses that may cause knee pain and how such condition is diagnosed.

Anatomy of the Knee

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Hard Structures Of The Knee Joint

The knee joint is surrounded by four hard structures or bones which are medically classified as the femur, tibia, patella, and fibula.


The femur is not only the longest but the strongest bone in the human body, which extends from the hip to the knee. This bone provides the support that enables the muscles of the upper leg to function.


Also known as the shinbone, this second longest bone inside the human body is one of two bones that connect the ankle to the knee. The shinbone helps support the body's weight and allows individuals to flex and maneuver the lower regions of their legs.


More commonly referred to as the kneecap, this structure is located between the shinbone and femur. The patella's major function is to provide protection for the softer tissues located in the knee.


Also situated in the lower leg, this bone runs parallel to the tibia and, along with that structure connects the knee and ankle thus enabling the muscles and tissues of the lower leg to properly function.

Soft Tissues Of The Knee

In addition to bones, the knee is comprised of several soft tissue structures that promote the joint's ability to move, flex and support the body's weight when an individual stands, walks, exercises or engages in any other activity requiring leg movements. Soft tissues are referred to in medical terms as cartilage, ligaments tendons, muscles, capsules and bursa. Noted knee soft tissues include: the meniscus, the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the lateral collateral ligament (LCL) and the medial collateral ligament (MCL).


The knee contains two cartilage-filled structures known as menisci. The menisci provide a protective space that prevents the femur and tibia from coming into contact.  They act like a shock absorber within the knee joint.

Anterior Cruciate Ligament (ACL)

This piece of soft tissue connects the tibia and femur. The ACL's other primary responsibility is to keep the tibia from sliding into the femur.

Posterior Cruciate Ligament (PCL)

The PCL also conjoins the femur and tibia. However, the other main purpose of this ligament is to prevent the tibia from sliding into the femur from a backwards angle. Both ACL and PCL help maintain the knee's stability and prevent the primary joint from overextending.

Lateral Collateral Ligament (LCL)

Located directly outside the knee proper, the LCL joins the femur's outside bottom region to the fibula's external top end. In addition, this structure controls the amount of force the knee is typically exposed to.

Medial Collateral Ligament (MCL)

Situated inside the knee proper, this collection of soft tissue connects the femur's bottom, inside region to the fibula's internal top section. The MCL's other major duty is to prevent the force from impacting the knee's inner region. Both the MCL and LCL also limit the amount of side-to-side motion the knee experiences.

Knee Muscles

Muscles located in or around the knee are the quadriceps, hamstrings, and calves.


The "quads" as they are sometimes nicknamed, extend from the thigh to the knee and enable the knee joint to extend and the leg to move.


These muscles are located in the back of the legs and also extend from thigh to knee. These structures support the legs but also enable individuals to bend and flex their knees.


The calf muscles extend from the knee to the foot and support the knee's ability to support and flex the lower leg regions.

Knee Joint Capsule

The knee capsule is located atop the knee and joins the kneecap, tibia, and femur together. Moreover, the capsule contains a lubricating liquid known as synovial fluid. This substance flows through the capsule and ensures that the knees hard structures remain strong and flexible.


The knee bursa is a fluid-filled structure surrounding separating the knees bones and tendons, which prevent such structures from coming into contact during movement.

Function of the Knee

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The knee is integral to leg mobility. Because the joint is designed to flex and bend like a hinge, people with healthy knees are able to bend, flex and exercise their legs. Moreover, knee joints are created to withstand a great deal of pressure, which enables the structures to support a person's weight when they stand, walk, run or engage in any kind of physical activity. The knee joint also connects the hard structures and soft tissues of the lower leg with their counterparts situated in the limb's upper part.

The knee provides us with a great deal of motion and mobility.  Unfortunately, it also is vulnerable to wear and tear as well as injury due to its constant use.  Those who protect the knee and care for their knees often go through life without much difficulty.  However, those who overuse their knees or face injuries may often end up with pain or other issues down the road.

Conditions that Cause Knee Pain

A variety of injuries and illnesses might precipitate knee pain. The discomfort experienced by the stricken individual will depend upon several factors including the specific location of the injury or illness, the condition's severity, as well as external issues such as the patient's:

  • Age
  • Weight
  • Physical condition
  • General health

Furthermore, knee pains could arise from acute injuries, damage precipitated by overuse of joint, in addition to several chronic medical conditions.

Acute Knee Injuries

Acute injuries are typically the result of blunt trauma caused by sudden accidents such as automobile wrecks, falls, or athletic injuries.  In cases of significant impact, fractures of the bones of the knee could occur.

Acute injuries that could impact the knee include:


Fractures are breaks to any of the bones surrounding the knee joint. These bone cracks can range in severity from a slight break to complete and total shattering of the hard structure in question. The most severe bone breaks could result in the impacted bone protruding through the afflicted person's skin.

Mild fractures of the bone can cause some pain or inflammation, but does not always prevent loss of mobility.  However, moderate to severe fractures can cause more intense pain, significant swelling and lack of mobility.

Ligament Tears

Some of the most commonly seen mishaps are ligament tears. Often occurring during an awkward fall, unusual stretching or knee extension or excessive application of force to the impacted knee region, the ACL, PCL, LCL or LCL could be subject to significant trauma that could culminate in a partial or full-blown tear. Ligament tears are sometimes also referred to as sprains. Sprains are typically graded in terms of the tear's severity ranging from grade 1 (minor) to grade 3 (severe).

Regardless of the specific ligament involved, tears often produce intense pain. Additionally, such events typically cause a significant degree of swelling and could result in limited mobility issues or, quite possibly, the complete inability to move the impacted knee or stretch the affected leg. The severity of associated symptoms might also vary depending upon the injury's severity.

Meniscus Tears

When the knee is exposed to unexpected trauma or is stretched or flexed beyond its normal capacity, the cartilage contained within each structure's menisci can tear. Meniscus tears may develop suddenly or damage contained within said structures may develop over time and eventually result in full-blown tears.

The condition can, however, produce symptoms that might indicate an acute problem. Such manifestations include knee swelling, as well as pain that can lead to difficulty engaging in everyday activities such as climbing stairs or walking uphill.

Muscle Strains

Strains related to the knee muscles often happen as the result of the quadriceps and hamstrings being overextended. In severe instances, said muscles can be torn. Sports related activities like running, jumping or stretching often precipitates knee-based muscle injuries.

The most common physical manifestation of an acute knee muscle injury is sharp pain in the front or back of the impacted leg muscles. Depending on the severity of the pull, swelling might occur. Moreover, more serious injuries may also result in the stricken individual's inability to bend or stretch their knee.

Overuse Injuries

Overuse injuries usually occur as the result of prolonged exercise or activities that tax the knee and its internal structures. Some of the more common injuries precipitated by overuse are:


Athletes or anyone who repeatedly bends their knees is at risk of developing bursitis. The condition results when the bursa becomes inflamed. Symptoms usually include mild to moderate pain and swelling on or surrounding the stricken person's kneecap. If the pain is bad enough, the affected person might experience some degree of difficulty walking.


Tendonitis occurs in tendons, soft tissue structures connecting muscles to bones. Among the most common knee tendon to fall prey to this condition is the patellar tendon, which conjoins the shinbone and kneecap. Repetitive exercise can strain the structure thus resulting in mild to moderate pain and inflammation near the kneecap.

Knee Dislocation

Also precipitated by prolonged periods of exercise or other forms of overuse, a dislocated knee typically occurs when the kneecap shifts out of position. Symptoms of a dislocation can include pain and swelling toward the knee's top.

Chronic Medical Conditions


This type of arthritis impacts joints such as the knee. Often affecting people older than 50-years-of-age or those who have sustained previous knee injuries, osteoarthritis is categorized by swollen, painful and stiff knees that may be difficult to move or bend. Once the condition arises, it typically worsens over a gradual period until treatment is administered.

Rheumatoid Arthritis

This form of arthritis can be quite serious and result in pain and swelling in affected joints like the knees. Rheumatoid Arthritis, or RA as the condition is known to certain medical practitioners, can cause significant illness and disability.


This ailment occurs when the body experiences a buildup of a substance known as uric acid. When uric acid forms excessively, it typically crystallizes and collects around joints such as the knee. Gout pain often occurs at night, can be extreme and result in mobility problems.


A doctor might need to employ several steps and diagnostic tests to determine the exact cause of one's knee pain. First, the physician will perform a physical examination and ask the patient questions related to when the pain started, the severity level and the activities the patient did or still doing that may cause the pain.

After the examination is performed, the physician might order further diagnostic tests based upon the specific conditions said professional may suspect. Such tests include:

Radiological Tools

Tests like X-Rays or Magnetic Resonance Imaging (MRI) studies give doctors the ability to examine bodily structures such as bones or soft tissues and thereby determine the specific injury or ailment that has occurred. Conditions like sprains, fractures, and arthritis might be discovered following a radiological test.


This is a medical procedure that entails a physician extracting fluid from the knee. Once the fluid sample is taken, the substance is transferred to a laboratory where doctors can study its contents and determine if it contains any potential pain-inducing precipitators. Diagnoses of ailments like arthritis, gout, and bursitis can be made after employing this technique.

Blood Tests

Blood samples might be administered to diagnose specific ailments such as arthritis and gout.


Knee pain can be debilitating. On certain occasions, such discomfort might be the result of a short-lived, relatively minor problem. In other cases, knee pain might indicate the presence of a more significant injury or illness requiring diagnosis and treatment.

For some mild to moderate causes of knee pain, the recommended treatment protocol could include rest or the administration of over-the-counter pain and inflammation relievers. However, when discomfort is precipitated by more serious injuries or illnesses, remedial efforts might require physical therapy or surgery. Your treatment will depend upon the severity of the condition, as well as your age, health and potential tolerance to specific therapeutic protocols. Speak with us to know more.



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