Diagnosing Knee Pain

  • Knee pain is common, especially as one gets older. It might also be an overuse injury.
  • New pain can result from a debilitating illness, such as knee arthritis or an injury like a sprain. 
  • Diagnosing knee pain will involve a medical exam and diagnostic testing, including imaging such as X-rays and an MRI. 

Knee pain is a frequent complaint among adults. The typical cause of knee pain is normal wear and tear from daily activities, such as walking, bending, standing, and lifting. However, there are a few things you do in life that do not involve your knees somehow. 

Athletes are more prone to suffer from knee discomfort and issues. However, whether caused by aging or accident, knee discomfort may be inconvenient and even debilitating in some cases. Consider some potential causes of knee pain and how a physician might diagnose it. 

Readers may use Health Report Live to get the information they need to understand their knee pain. This article covers how a healthcare provider might diagnose knee pain.

Brief Anatomy of the Knee

The knee is one of the most critical joints in the body. It bears much of your body weight when you move, so it is at risk of injury. 

The components of the knee include:

  • The tibia: The large bone in the lower leg that you might know as the shin
  • The femur: The big bone in the thigh intersects with the tibia to form the knee joint. 
  • The patella: A bony cap that covers the joint to protect it

Connecting these bony pieces is a network of connective tissues, including cartilage, tendons, ligaments, and muscle. 

Cartilage covers the ends of the bones to absorb the shock as you move. Unfortunately, when the cartilage wears down, you develop osteoarthritis, a common cause of knee pain. 


Diagnosing knee problems involves several steps that help paint a picture of the health of the joint, starting with a medical history. The care team will look for a history of degenerative diseases such as rheumatoid arthritis. Understanding your medical history can help them find treatment options.

Medical History

Medical history gives healthcare providers a chance to learn more about you, your health, and your lifestyle. They may cover the basics, like what medication you currently take. 

Definitions and Key Diagnostic Distinctions  

A medical history will include rooting out the diagnostic distinctions that allow the clinician and care term to make a cohesive diagnosis. It is also a chance to define the patient complaints and assign them into categories that help diagnose the problem. 

Questions to Help Characterize Pain 

They will also ask questions specific to the injury, such as how you would characterize the pain and rate it on a scale of one to 10. The medical team may also want to know what you were doing when you first noticed the pain. 

For example, did it come on suddenly? Did you feel a pop or see a change in how your knee moves? 

Questions to Help Characterize Other Symptoms 

Taking a cognizant medical history also helps practitioners determine the occurrence of the pain. Acute refers to sudden pain and chronic indicates a reoccurring injury. When combined with physical examination, these questions can provide significant answers to what is causing the pain.

Physical Exam

The physical exam gives the healthcare provider a chance to learn more about the knee. How it moves, for example, and what happens when you feel pain. Do you feel it all the time or just when you walk? 

They may ask you to walk so that they can see the knee joint in action, too. They will look for key indicators of common injuries or diseases such as arthritis. 

The provider will delve more deeply into when and what type of pain you feel. Pain location can be a significant indicator. 

Overall, pain, for example, may mean something different from what occurs just on one side of the joint. 

All-Over Pain

Location is a key diagnostic tool when it comes to ligament injuries. All-Over knee pain would mean something different from an injury felt on the medial area of the joint. 

For instance, radiating pain that moves throughout the joint might indicate knee osteoarthritis more than ligament injuries. Likewise, pain in the middle of the joint may indicate menisci involvement instead of a torn ACL.

Imaging and Radiologic Tests

The doctor will most likely want to run some imaging tests. They offer visual indicators of what may be at the root of the pain, such as degeneration in the joint. Some standard imaging tests could include:

  • X-ray
  • Magnetic resonance imaging (MRI)
  • Computed tomography scan (CT scan)

There are also minimally invasive tests that can provide clues, such as an arthroscopy which requires a small incision to allow a tiny camera into the joint. 

In addition, a radionuclide bone scan requires a small amount of radioactive material injected into the bloodstream. That material helps to show how well blood flows in that area. 

Lab Tests

Specific lab tests can be indicators of overall health and might help pinpoint the diagnosis. A urinalysis, for example, can help diagnose certain forms of arthritis. Likewise, uric acid can mean gout. 

Blood Tests

Part of the lab workup could include blood tests. For instance, a hematocrit measures the number of red blood cells and can indicate inflammation. An antinuclear antibody test looks for essential antibodies in the blood that indicate arthritis. 

Removal of Joint Fluid

The removal of the joint fluid offers two benefits: to relieve the pain due to inflammation and help with the diagnosis. If there are white blood cells in the liquid, it might indicate there is an infection. 

Inflammation in the bursa, a cushion that helps protect the joint, can cause a build-up of fluid. Removing it is both diagnostic and therapeutic. 

Differential Diagnoses 

Knee pain is a broad problem with many possible causes. Differential diagnoses is a term that refers to the possibilities based on the symptoms. A healthcare provider could consider two or more possible causes of knee pain, such as ligament tear or osteoarthritis. 

The differential diagnoses allow the care team to narrow the search down and determine what further tests to do. 

What Are Some Common Knee Problems & How Do I Know What Type of Knee Pain I Have?

Only a healthcare professional can tell you what is causing your knee pain. There are several options to consider, though. 


Arthritis is a likely cause for many who experience knee pain, depending on your age. Knee joint arthritis is a severe, painful illness that worsens with age. 

The most frequent kind is osteoarthritis, affecting one or both knees. The symptoms include knee pain, edema, and stiffness.

Torn Anterior Cruciate Ligament (ACL)

Ligaments hold the knee joint bones together, and they can be fragile. The ACL sits in the center of the knee and helps control the tibia bone’s movement and rotation in the lower leg. 

An ACL injury can occur when you change direction quickly. This is an injury you see a lot in athletes like basketball players. Damage can also be because of trauma, like a direct hit to the leg’s soft tissue during a football game. 

The diagnosis criteria consist of a grading scale for all ligament damage. The scale serves to standardize the diagnosis criteria. A Grade I tear is partial, so some ligament remains intact. 

Grade II means partially torn; however, the damage is more significant than a Grade I injury. Grade III means complete severance. And Grade IV indicates more extensive damage to the whole joint structure. 

A Bruised Knee

When a bruise or contusion develops, the tiny blood vessels are injured, and blood seeps out under the skin. While a knee contusion is unpleasant and may make it difficult to walk or use your knee properly for a short time, it is an injury that usually heals rapidly.

A knee contusion is a minor sports injury caused by direct contact with the knee. You might see this injury after a fall or car accident. It might also be the result of sports play. 

Knee Dislocation

Typically, the kneecap or patella sits on top of a groove in the front of the knee. When the kneecap dislocates, it moves out of this groove, stretching or tearing the supporting tissues. 

This injury can occur due to a sharp change in direction. It is a common injury for dancers and athletes. 

Pain on Inside of Knee

Medial knee pain occurs on the inside of the knee or the side close to the other leg. This is a symptom of possible knee injuries, including a torn medial collateral ligament or ACL. 

An MCL (Medial Collateral Ligament) Injury

The MCL sits on the inner side of the knee. A tear to this ligament can affect the stability of the knee joint. Injury to the MCL is common in sports, especially football, skiing, basketball, or rugby.  

Injury to the Medial Meniscus

A medial meniscus tear occurs when the knee (cartilage tissue) on the meniscus is torn. Injuries to the medial meniscus are more common than injuries to the lateral meniscus and can cause discomfort, stiffness, swelling, locking, catching, or buckling.


Bursitis refers to inflammation of the bursae, a fluid-filled sac that helps cushion the joint. Joints have many hard, sharp areas and the bursae reduce the friction between them. 

There are several bursae in the knee joints, and any of them can develop inflammation. The most common knee bursitis occurs in the bursa over the kneecap or on the medial or inner side of the joint. 

Pain on Outside of Knee

Pain on the lateral or outer side of the knee is an injury on the side facing away from the body. Distance runners frequently experience lateral knee soreness. However, an injury that twists the knee or forces it away from the opposite leg might cause lateral knee discomfort.

Iliotibial Band (“IT Band”) Syndrome

The iliotibial band is the thick connective tissue from the shinbone to the hip bones. This band slides around the outside bottom border of your thigh bone as you bend and extend your leg. 

Movement of the iliotibial band may irritate adjacent tissues, causing discomfort with repetitive bending and stretching of the knee.

The exact cause of iliotibial band syndrome is not clear. However, it is a common injury in sports, especially for distance runners. It may have something to do with the repetitive bending of the knee. 

Injury to the Lateral Collateral Ligament (LCL)

The LCL is another of the four ligaments supporting and stabilizing the knee joint. The LCL sits on the outer or lateral side of the knee and goes from the top of the fibula, the bone on the inside of the calf, to the outer side of the femur or thigh bone. LCL injuries often occur in athletes, especially runners. 

Pain on the Front of the Knee

Anterior knee pain or pain in the front of the joint can have many causes. Typically, it involves an injury to the patella or the tissue that supports it. 

Patellar Tendonitis (aka Jumper’s Knee)

Patellar tendonitis can cause pain in the front of the knee. This injury affects the patellar tendon that connects the kneecap to the shin. Jumper’s knee refers to the potential cause of the injury. Jumping weakens the tendon and can cause inflammation and pain. 

Runner’s Knee

Runner’s knee is another cause of pain in the joint’s front. It is more of a symptom than a condition, though. It describes a problem you might experience with several injuries to the kneecap. 

As the name suggests, it is a common symptom of a knee injury that occurs in those who run a lot. 

Pain Behind Knee

Pain behind the knee typically infers arthritis, although there are other possibilities. It could also indicate an injury to the thigh, such as biceps femoris tendonitis, hamstring, or quadriceps problems. 

Potential knee problems that can cause this pain include Baker’s Cyst and Jumper’s Knee. 

Baker’s Cyst

A Baker’s cyst is a fluid-filled sac that can form behind the knee. The sac fills with the fluid that lubricates the knee. A cyst like this can be a symptom of a more severe knee problem, such as arthritis. The body produces excess fluid to help the damaged joint function. 

Injury to the Posterior Cruciate Ligament or PCL

Posterior refers to behind the knee, so this is an injury to the ligament that goes from the upper part of the leg to the calf, stretching behind the knee joint. Although anyone can experience this injury, it happens with athletes, particularly skiers. 

Inflammation in the Knee

Inflammation in the knee is a broad symptom of most common knee injuries. It means swelling in some part of the knee joint or the supporting tissue. 

How Do I Know if My Knee Pain Is Serious?

While it is always a good idea to see your doctor for chronic pain, a minor knee injury could heal. 

Some signs you need a doctor include the inability to put weight on your knee, significant swelling, reduced range of motion or movement in the joint, or if you can see something is wrong with the knee. 

You will also need a doctor if you run a fever. That might show an infection in the joint. 

What Does Inflammation in the Knee Feel Like?

Pain is not the only indicator that there is a problem. The knee might also feel warm or look swollen. You might only feel pain if you push on it.

Treatment for Knee Problems

Treatment can involve anything from elevation to over-the-counter medication for pain relief to surgery. If the pain is mild or new, an excellent place to start is with rest and icing. 

If the pain persists, you need to see a sports medicine specialist or an orthopedic or orthopaedic doctor for medical advice. and physical therapy.

Sean Byers, MD

Sean Byers, MD

Sean Byers is currently a Resident in the Internal Medicine program at UTMB. He studied at the University of Queensland School of Medicine as well as received his Master’s in Public Health with a focus in epidemiology and biostatistics at the University of Southern California. His background is in biology, computer science, public health, and internal medicine.

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