Causes of knee pain

Introduction
There are surprisingly large number of causes of pain in the knee. The good thing about the knee is that it is made of 3 distinct compartments- the medial (inside) and lateral (outside) and patello-femoral (front or anterior) compartment. Also because the knee is just under the skin, it becomes very easy to diagnose the cause of the pain. By looking at the age , location and mechanism of injury therefore one can make a very reasonable diagnosis of the cause of the pain.

Causes of pain by age

Children and adolescents

-          Jumper’s knee (patellar tendonitis)

-          Juvenile rheumatoid arthritis

-          Osteochondritis dissecans

-          Patellar subluxation

-          Referred pain: slipped capital femoral epiphysis, hip fracture

-          Tibial apophysitis (Osgood-Schlatter lesion)

-          Trauma: ligamentous sprains (anterior cruciate, medial collateral, lateral collateral), meniscal tear, fractures including epiphyseal fracture , muscle strains

 

Young adults

-          Inflammatory arthropathy: rheumatoid arthritis, Reiter’s syndrome, Pigmented villonodular Synovitis

-          Medial plica syndrome

-          Patellofemoral pain syndrome (chondromalacia patellae)

-          Pes anserine bursitis

-          Septic arthritis

-          Stress fracture/Stress reaction

-          Tendonitis (quadriceps, Patellar tendon, etc)

-          Trauma: ligamentous sprains (anterior cruciate, medial collateral, lateral collateral), meniscal tear, fractures, muscle strains

-          Referred Pain: neurogenic, hip and leg pathology

 

Older adults

-          Crystal-induced inflammatory arthropathy: gout, pseudogout

-          Osteoarthritis

-          Popliteal cyst (Baker’s cyst)

-          Metastatic cancer

Common Knee pain by Anatomic Site (Figure 1)

Anterior knee pain

-          Jumper's knee (patellar tendonitis)1

-          Patellar subluxation or dislocation2

-          Patellofemoral pain syndrome (chondromalacia patellae)3

-          Tibial apophysitis (Osgood-Schlatter lesion)4

Medial knee pain

-          Medial collateral ligament sprain5

-          Medial meniscal tear6

-          Medial plica syndrome7

-          Pes anserine bursitis8

Lateral knee pain

-          Iliotibial-band tendonitis9

-          Lateral collateral ligament sprain10

-          Lateral meniscal tear11

Posterior knee pain

-          Popliteal cyst (Baker's cyst)12

-          Posterior cruciate ligament injury13



Figure 1. Sites of pain of typical conditions of the knee. Numbers refer to superscript numbers under anatomical site.

Mechanism of Injury

Trauma                    

-          Fracture of femur, tibia, fibula, patella

-          Ligamentous sprain (ACL, MCL, LCL, PCL)

-          Meniscal tear

-          Muscle strain

-          Osteochodral fracture

-          Patellar subluxation/dislocation

 

Atraumatic   

-          Medial plica syndrome

-          Osteoarthrits

-          Patellofemoral Syndrome

-          Popliteal cyst

-          Rheumatoid or other inflammatory arthritis (pigmented villonodular arthritis, gout, Reiter's syndrome)

-          Septic arthrits

-          Stress fractures/reactions (tibial plateau & shaft, femur, patella)

-          Tendonitis

-          Referred pain (hip osteoarthritis, lumbar radicular symptoms)

-          Metastatic cancer