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Knee Swelling or Swollen Knee: Symptoms, Causes, Diagnosis, Treatment

Swelling of the knee joint is fairly common and can be found in a variety of conditions.1 It is also known as knee effusion or water on the knee. The swelling of the knee can be acute, which lasts for a short duration or of chronic type, which lasts for a longer period.

Knee Swelling or Swollen Knee

As there are various causes of knee swelling or swollen knee, precise diagnosis can be challenging; hence it is important to have a planned approach towards determining the exact cause of knee swelling. This can help in proper treatment and further management of the knee joint or a systemic condition.

How Does Knee Swelling or Swollen Knee Develop?

Knee swelling, in simple terms, is accumulation of excess fluid in or around the knee joint area. While synovial fluid in the joint naturally lubricates and nourishes the joint, excess fluid can be due to some underlying cause. While the fluid can get accumulated in the joint space, it can also get accumulated outside the join space and affect the soft tissues surrounding the joint.

Similar to fluid accumulation, certain situations like injury or other conditions can also lead to bleeding in the joint area. In case of injury, it occurs soon, with intense swelling and can be very painful.

Signs And Symptoms Of Knee Swelling Or Swollen Knee

Knee swelling or swollen knee can develop spontaneously or may come on gradually over a period of few days. There may be an obvious injury or difficult in movement or it may be preceded by history of excess strain of the knee joint. It can also occur in a knee joint, which has a previous injury or a known joint condition.

A swollen knee can cause stiffness, with a feeling of heaviness and make movement uncomfortable. There is difficulty in bending and straightening the leg, thus affecting the range of motion (ROM). Weight bearing activities like standing or walking may be difficult or almost impossible depending on the severity of the knee swelling.

What Can Cause Knee To Swell?

The causes of knee swelling are many and the nature of the swelling along with proper history taking can guide in determining the possible causes. It is important to understand whether the knee swelling had a rapid or a gradual onset. The most common causes of knee swelling include

Knee Injury

There is rapid swelling after a knee injury. Any injury causing swelling of knee joint occurs when some of the joint structures or soft tissues get damaged. The knee swells up immediately, may sometimes appear bruised and is very painful and sore.2

  • Acute knee injuries like ligament tear, meniscus tear, dislocations and fractures are common. With injuries like Anterior Cruciate Ligament (ACL) tear and fractures of the bone, there may be accumulation of blood within the joint, called hemarthrosis.
  • Some knee injuries may not cause bleeding but lead to acute swelling of the knee. For example, meniscus tear or overstretching of knee joint ligaments in knee sprain.

Swollen Knee Due To Arthritis

These may include joint conditions that are exacerbated leading to knee swelling.

Gradual Onset of Knee Swelling

  • This can occur due to conditions like osteoarthritis, rheumatoid arthritis and other types. It may commonly occur due to wear and tear of the knee joint, after joint overuse causing increased irritation of the tissues or as an autoimmune response.

Rapid Onset of Knee Swelling Without Any Injury

  • This can occur due to gout or pseudogout, which occurs due to affected metabolism and lead to formation of crystals in the joint.
  • Certain infections can cause rapid swelling in the joint. Septic arthritis or infective arthritis can occur due to presence of infection in the body that spreads to the knee joint. Other infections like gonorrhea, tuberculosis, Lyme disease and some rare infections can also be the cause. In most cases, systemic symptoms and fever is commonly present.

Other Causes Of Knee Swelling Or Swollen Knee

Conditions like prepatellar bursitis causing fluid accumulation outside the knee joint space or baker’s cysts, a swelling behind the knee needs to be properly evaluated. On some occasions, benign or malignant tumors or some vascular conditions may also lead to knee swelling. In such cases associated symptoms are assessed and appropriate investigations are carried out.

How Is The Knee Swelling Or Swollen Knee Diagnosed?

For exact diagnosis of knee swelling or swollen knee certain investigations that may be useful, include

  • Blood tests to determine inflammatory joint disorders and infections
  • X–ray of the joint to find out any obvious bone injury or bony changes specific to joint disorders
  • MRI scan to rule out ligament and meniscus injuries, to evaluate previously injured or operated joints.
  • Synovial Fluid Analysis – In case of severe or tense effusion, joint aspiration may be performed and synovial fluid may be removed. This offers relief in pain and the fluid can be sent for laboratory analysis to detect presence of cells, blood, crystals or infective organisms.

Treatment For Knee Swelling Or Swollen Knee

Treatment For Knee Swelling Or Swollen Knee

While the proper course of management depends on the precise diagnosis, some measures that are useful in most cases of knee swelling or swollen knee include

  1. R.I.C.E. Formula For Knee Swelling or Swollen Knee

    • Rest – Avoiding weight bearing activities can provide rest to the knee joint.
    • Ice – Applying ice wraps and proper ice therapy can help in reducing knee swelling and pain.
    • Compression – Applying bandage to the area can help.
    • Elevation – Raising the leg and resting it at a comfortable elevated position is useful.
  2. Treatment of Knee Swelling or Swollen Knee

    Knee Pain and knee swelling can be controlled by prescribing anti-inflammatory drugs. Other associated complaints are treated symptomatically.

  3. Joint Aspiration For Treating Knee Swelling or Swollen Knee

    In case of large knee effusion causing great discomfort, the excess synovial fluid can be drained by aspiration, which helps to reduce pain and swelling

  4. Steroid Injections For Knee Swelling or Swollen Knee

    Injections of steroid into the joint space may help to reduce inflammation and pain.

  5. Physiotherapy For Knee Swelling or Swollen Knee

    Based on the underlying condition, appropriate physical therapy measures may be planned.


Also Read:

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:July 5, 2019

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