Knee Pain

Chronic knee pain affects up to a quarter of all adults and can be debilitating. The knee has the largest articular surface in the body, and has to support up to five times a person’s weight.

The causes of knee pain can be divided into:

  • Knee pain from trauma
  • Knee pain not from trauma but with swelling (effusion)
  • Knee pain not from trauma and without any swelling (effusion)
  • Knee pain that actually arises from elsewhere
  • Uncommon causes

Pain that starts immediately after trauma usually points to actual structural damage to the knee. Delayed pain after trauma usually involves strains and sprains to tendons, cartilage and small tears in tissues. Pain that is over the front of the patellar and associated with sprinting and jumping may point to issues with the patellar tendon. Pain that can be localised with pinpoint accuracy usually arises from a tendon, ligament, or other structures that can be easily felt that is closer to the surface. Pain that is vague to localise may arise from a structure deep in the joint and may be associated with an infection, autoimmune condition, or is pain “referred” from another site (i.e. nothing to do with the knee at all but is sensation transmitted by nerves mimicking as knee pain).

Rapid swelling after knee trauma usually points to bleeding into a joint and is associated with more tissue damage, whereas swelling that is without trauma usually indicates an infection, auto-immune disease or conditions such as gout. There will be more reason to worry if there is fever, chills, night sweats, rashes, and malaise. There is often a need for fluid to be taken from the knee and examined in order to find out exactly what is wrong. Small amounts of effusion may be difficult to detect without the use of an ultrasound scanner.

If many joints are affected, not just the knee, this might mean that there is a more widespread problem like an autoimmune disease like rheumatoid arthritis, or infection or cancer.

Common causes of knee pain after trauma include:

  • Patella tendon tear or dislocation
  • Medial or lateral collateral ligament tear
  • Anterior cruciate ligament tear
  • Meniscus tear
  • Intra-articular fracture
  • Osteochondral defect

Less common causes of knee pain after trauma include:

  • Patella or fibular fracture
  • Knee dislocation
  • Posterior cruciate ligament tear or quadriceps tendon tear
  • Bone contusion

Causes of knee pain with swelling and not related to trauma:

  • Worse with movement
    • Osteoarthritis
    • Osteochondral defect
  • Not worse with movement
    • Infection in the joint
    • Gout or pseudogout
    • Rheumatoid arthritis
    • Widespread gonococcal infection

Causes of knee pain without swelling and not related to trauma:

  • Anterior (front) of knee:
    • Quadriceps and patellar tendinopathy
    • Bursitis
    • Plica syndrome
    • Osgood-Schlatter disease
    • Hoffa’s fat pad syndrome
    • Patellofemoral pain,
    • Chronic patella subluxation
    • Patellar stress fracture
  • Medial (inner aspect) of the knee
    • Pes anserine bursitis
    • Medial meniscus tear
    • Saphenous nerve entrapment
  • Lateral (outer aspect) of the knee
    • Iliotibial band syndrome
    • Lateral meniscus tear
  • Posterior (back) of the knee
    • Baker’s cyst
    • Popliteus tendinopathy
    • Popliteal artery aneurysm

Treatment of knee pain will depend on the underlying cause. Treatment can range from simple pain killers taken orally, to minimally invasive procedures to open surgery.