knee pain differential diagnosis – A comprehensive guide

There are several reasons behind knee pain. In order to properly diagnose and treat knee pain, it is essential to consider various differential diagnoses for knee pain.  Here we will discuss possible reasons for knee pain. 

Knee pain differential diagnoses include Arthritis, Osteoarthritis, Ligament, and tendon injuries, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) Bursitis, Fractures,  Baker’s cyst, and Infection.

Anterior knee pain differential diagnosis

Anterior knee anatomy is the pain at the front of the knee and sometimes in the center of the knee.  It is a common type of knee pain caused by conditions such as patellofemoral pain syndrome, chondromalacia patella, or runner’s knee.

Chondromalacia patellae :

Chondromalacia patella is a condition that affects the underside of the kneecap (patella).  It is characterized by the softening and degeneration of the cartilage on the back of the patella—resulting in pain, stiffness, and a grinding sensation in the knee.

Patellofemoral pain syndrome:

(PFPS) it is a short form of Patellofemoral pain syndrome. it is  also known as “chondromalacia patellae”

means pain in the front of the knee, around the patella, or behind the kneecap. The condition is also known as runner’s or jumper’s knee and affects all age groups. It occurs when the patella does not move smoothly over the femur (thigh bone) and instead rubs against it, leading to the wearing down of the cartilage under the patella. It is considered one primary reason for differential diagnosis of knee swelling.


  • overweight body weight
  • Weak muscles
  • Improper  sports training techniques
  • Changes to footwear
  • Uncomfortable playing surfaces
  • Overuse of the knee joint
  • Problems with kneecap alignment

Tibial apophysitis (Osgood-Schlatter lesion)

Tibial apophysitis, also known as Osgood-Schlatter lesion, is a condition that affects the growth plate (apophasis) near the knee in adolescent athletes. It occurs when the patellar tendon pulls on the growth plate, causing inflammation and pain at the tibial tubercle (the bony bump located just below the knee joint).

Jumper’s knee (patellar tendonitis)

Jumper’s knee also known as patellar tendonitis, is an  injury that affects the patellar tendon, which connects the kneecap (patella) to the shin bone (tibia )

it is seen in sports-related persons who are engaged in high-impact sports, such as basketball, and volleyball, and causes. it is the result of repetitive jumping puts stress on the patellar tendon and it leads to damage to tissues.

Medial knee pain

The medial collateral ligament MCL is a knee injury that happens by sudden twisting, stretching, and bending of the knee. that results in a torn ligament. ligament runs along the inner side of the knee and helps to stabilize it. When your MCL is damaged, your knee can over-extend itself, or bend too far in a direction that it’s not supposed to bend. You may heal on your own with basic care, rest, and rehab. But if your injury is severe, you may need to have surgery.


  • the sudden hit of any force
  • sudden twisting
  • injury by throwing on ground injury by throwing on the ground

Meniscal  tear :

The meniscus in our knee lies between the tibia (lower leg bone) and the femur (thigh bone) and gives support from any shock and disturbance created by our body weight. it protects our lower part. in a meniscal tear this cartilage in the knee joint names the “meniscus” is damaged.

  • A direct impact
  • Due to Degenerative changes
  • Due to Repetitive & Overuse
  • weaken of knee’s cartilage


Arthritis in the knee is a common form of joint pain that occurs when the cartilage in the knee joint wears down over time, leading to inflammation. osteoarthritis is the most common type of arthritis rheumatoid arthritis and post-traumatic arthritis. Osteoarthritis is a degenerative condition that occurs as the protective cartilage in the knee wears down over time.  bursitis results in, difficulty in walking up and walking down stairs, and trouble in standing for long periods of time.


Bursitis is a knee disease that occurs when the fluid-filled sacs (bursae) near a joint become inflamed. Bursae are located between bones, tendons, and muscles and serve to reduce friction and cushion the joint during movement. The skin over the affected joint may appear red and warm to the touch.

Bursitis of the knee can be quite painful, and the pain can decrease mobility.  People who spend a lot of time kneeling on hard surfaces are at higher risk for developing this type of knee bursitis. Knee bursitis may also occur after a traumatic injury, like a blow to the knee.

Causes: includes infection, and underlying medical conditions, such as arthritis.

Lateral knee pain

Lateral knee pain is a type of knee pain that occurs on the outer side of the knee. It may appear over a period of time or may develop suddenly after an injury.

 This is a condition that occurs when the iliotibial band, a thick band of tissue that runs along the outside of the knee, becomes tight and rubs against the lateral femoral epicondyle.

 damaged lateral collateral ligament (LCL),  Injuries to the LCL, such as sprains, can cause lateral knee pain.

Iliotibial Band Syndrome

It occurs when the iliotibial band, a thick band of tissue that runs along the outside of the knee, becomes tight and rubs against the lateral femoral epicondyle, causing friction, pain, and inflammation. ITBS is commonly seen in runners and cyclists.

Reasons: overuse, muscle tightness and weakness, running, flat feet, and a sudden increase in activity.

Hamstring Tendinopathy

Hamstring Tendinopathy is a condition characterized by pain and discomfort in the tendons that run along the back of the thigh. It is commonly seen in athletes, especially those who engage in high-intensity sports such as running and jumping.

  • Aging
  • acute injury
  • repetitive jumping or kicking
  • due lot of acceleration and deceleration work

Lateral Collateral Ligament LCL

LCL ligament that provides stability to the outer aspect of the knee.

Causes: LCL injuries include

  • sudden twisting or stretching of the knee
  • direct trauma, or overuse
  • Sudden twisting
  • awkward fall where the lower leg is forced inwards, a blow to the inside of the knee

Lateral Meniscus Tear

sudden onset from awkward knee twisting esp if knee bent and foot planted. Gradual onset from wear and tear.

Posterior knee pain

There are various types of posterior pain .in the posterior knee pain differential diagnosis it is found that knee pain occurs on the back side of the knee it is known as posterior knee pain. The PCL is a ligament that provides stability to the back of the knee. Injuries to the PCL can cause posterior knee pain. further, it can be divided into two, as Sudden onset (acute) ,Gradual onset (chronic).

Acute pain behind the knee

Acute pain behind the knee is a sudden and severe discomfort or pain in the back of the knee. The following are common acute injuries that cause pain in the back of the knee:

Hamstring tendon strain -The most common is a Biceps femoris tendon strain. A hamstring avulsion strain occurs if the tendon pulls a small fragment of bone with it.

Biceps femoris tendon avulsion– An avulsion strain occurs when a tendon tears, pulling a small piece of bone with it. Symptoms of an avulsion  ~strain are Sudden severe pain at the back of your knee.

  • Sudden swelling
  • Tenderness at the back of your knee

Biceps femoris tendon avulsion

A Biceps Femoris Tendon Avulsion is a condition in which the biceps femoris tendon, which connects the biceps femoris muscle to the knee, becomes torn or pulled away from the bone. This can cause sudden, severe pain and swelling in the knee and can limit movement and activity.

Chronic pain behind the knee

Chronic pain behind the knee is a persistent discomfort or pain in the back of the knee that lasts for an extended period of time. Pain at the back of the knee which occurs gradually is often overuse related.

Baker’s Cyst

A Baker’s Cyst, also known as a popliteal cyst, is a fluid-filled sac that develops behind the knee. It is caused by the buildup of fluid in the knee joint and can be caused by conditions such as knee osteoarthritis, rheumatoid arthritis, or a knee injury.

Gastrocnemius tendinopathy

Gastrocnemius Tendinopathy is a condition in which the gastrocnemius tendon, which connects the gastrocnemius muscle to the heel bone, becomes damaged or irritated.  It is commonly seen in athletes and individuals who engage in activities that involve running, jumping, and sudden changes in direction.

Biceps femoris tendinopathy- biceps femoris tendon, it connects the biceps femoris muscle to the knee and becomes damaged or irritated. This can cause pain, swelling, and stiffness in the knee and lower leg.

joint effusion

If your knee looks larger than usual, you might have joint effusion (a swollen joint). Joint effusion can be a sign of an injury, a type of arthritis or another condition. Joint effusion in the knee is a condition where there is an accumulation of excess fluid within the knee joint. This can cause swelling and increased pressure within the joint, leading to pain, stiffness, and decreased range of motion.

Kneecap dislocation

kneecap dislocation occurs when the round-shaped bone covering the knee (patella) moves or slides out of place it may also occur as result of direct trauma. When the kneecap is dislocated, it can slip sideways to the outside of the knee. If your knee is dislocated, your thigh and shin bones may be completely or partially out of place. A dislocated knee is different from a dislocated kneecap. That’s when your kneecap (patella) slips out of place .


  • Car accidents
  • Sports injuries
  • Hard falls


Fractures of the knee can occur in any of the bones that make up the joint, including the thighbone (femur), shinbone (tibia), and kneecap (patella).

Knee fractures (patellar fractures) are typically caused by direct falls to the knee or sharp blows to the knee. Car accidents are another common cause of knee fractures. In rare cases, the knee can be fractured due to a sudden contraction of a quadricep where the muscles can pull from the patella .


Gout is a type of arthritis that is caused by the buildup of uric acid crystals in the joints. The knee is one of the most commonly affected joints in gout. This condition can cause sudden and severe pain, swelling, and redness in the affected joint.

 The pain is often described as throbbing or aching and can be accompanied by stiffness and limited mobility. Gout can also cause additional symptoms such as fever, fatigue, and a general feeling of malaise. The buildup of uric acid crystals in the knee joint can lead to long-term damage and chronic inflammation if left untreated.


We tried to cover all possible reasons or diagnosis behind the knee pain, the reasons and severity of disease may vary from person to person.  In order to properly diagnose ,  medical examination and imaging tests may also be necessary to accurately diagnose the cause of knee pain.

Frequently asked questions ( knee pain differential diagnosis )

What are the five most common knee problems?

Osteoarthritis , Meniscus tear ,Anterior cruciate ligament (ACL) injury, Posterior cruciate ligament (PCL) injury and Patellofemoral pain syndrome .

What are the common knee injuries?

Common knee injuries include sprains and strains, dislocations, fractures, meniscus tears, and anterior cruciate ligament (ACL) injuries. These types of injuries can result from sudden impacts, overuse, or improper movement.

What is knee bursitis?

Knee bursitis is inflammation of the bursae (small fluid-filled sacs) around the knee joint, causing pain, swelling, and stiffness. It can be caused by overuse, injury, or underlying medical conditions.

what is LCL ?

The lateral collateral ligament (LCL) is a ligament located on the outer side of the knee that helps provide stability to the joint.