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Sudden Knee Pain? Here's 7 Possible Causes

The onset of sudden pain in your knee can be especially worrying — pain is often a sign that something has gone wrong in the area; or worse, a symptom of a more severe medical condition.  

Instead of playing the guessing game, understanding the potential causes of sudden knee pain is the best way to find out the root of the pain, apply the right treatment early, and get you on the fast track to recovery. 

We’ve outlined 7 potential causes for sudden knee pain below along with their associated symptoms to help you identify what you may be dealing with. 


Common Causes of Sudden Knee Pain


1. Runner’s knee


Runner’s knee is a condition in which the kneecap becomes stressed from overuse or misalignment with the thigh bone. It is most commonly encountered in runners and is twice as likely to develop in women compared to men. 

Symptoms of runner’s knee: 

  • A dull pain in the kneecap

  • Popping, clicking or grinding sounds when bending the knee

  • Kneecap is tender to the touch


  • Icepacks applied to the knee for 20-30 minutes at a time for short term pain relief. 

  • Wearing a knee brace provided by a physiotherapist.

  • Performing knee and leg strengthening exercises prescribed by a physiotherapist.

Recovery time: 2-4 weeks for mild cases, 6-12 weeks for severe cases.  


2. Kneecap Fracture


Kneecap fracture, or patellar fracture, refers to a break in the kneecap due to impact from a fall or other accident. It’s a serious condition that renders affected individuals unable to walk or straighten the knee without extreme pain. 

Symptoms of kneecap fracture: 

  • Bruising and swelling of the kneecap

  • Inability to straighten the kneecap or keep the leg raised when seated. 

  • Inability to walk or stand up


  • Small fractures can be treated with the help of a brace or splint to keep the knee straight and restrict movement.

  • Surgery may be required if the breaking of the kneecap has resulted in displaced pieces of bone. 

Recovery time: 3-6 months, depending on the severity of the fracture. 

Causes of Sudden Knee Pain (Runners knee and Kneecap Fracture)


3. Gout


Gout of the knee can occur as a type of inflammatory arthritis that causes sudden and severe swelling around the knee. This condition is usually caused as a result of a high level of uric acid in the body, not physical trauma. 

Symptoms of gout in the knee: 

  • Swelling in and around the knee

  • Sudden pangs of pain in the knee

  • A change in skin colour around the knee

  • Area around the knee is tender to the touch


  • Taking over the counter anti-inflammatory medication, as well as medication prescribed by a doctor. 

  • Applying ice packs up to 20 mins at a time throughout the day. 

  • Raising the knee above heart level when possible. 

  • Avoiding the consumption of foods rich in purines such as alcohol, certain red meats, and seafood.

Recovery time: Gout is a chronic condition that will continue to show symptoms periodically. It can be managed with the above treatment methods to reduce the occurrence of symptom flares. 


4. Bursitis


Bursitis is a condition where the fluid-filled sacs (bursae) in around the knee become inflamed, resulting in pressure and pain in the knee. Impact trauma to the knee, as well as repeated friction in the knee joint from kneeling actions are common causes of bursitis. In some cases, the inflamed bursae can become infected. 

Symptoms of bursitis in the knee: 

  • Intense swelling on the front of the kneecap

  • Warmth within swollen kneecap

  • Pain when moving the knee

  • In the case of infection, the knee may appear red and leak fluid


  • Resting the affected knee until the bursitis clears up normally.

  • Applying ice packs to the swollen area up to 20 mins at a time daily.

  • Taking anti-inflammatory medicine as prescribed by a doctor. 

Recovery time: 2-8 weeks with proper treatment. Infection will prolong the recovery period. 

Causes of Sudden Knee Pain (Gout, Bursitis and Tendinitis)


5. Tendinitis


More commonly affecting elite athletes, knee tendonitis is a condition that arises due to repeated movements in the leg that gradually weaken the patellar tendon in the knee. If left untreated, the pain from this condition will worsen over time and affect range of movement. 

Symptoms of knee tendinitis: 

  • A dull pain under the kneecap, on the top of the shinbone 

  • Stiffness or loss of strength in the knee

  • Increasing pain or discomfort when placing pressure on the knee, such as when walking down stairs


  • Refrain from activities that trigger the pain.

  • Apply ice packs to the painful area up to 15 mins at a time.

  • Wearing a knee brace.

  • Doing specialised strengthening exercises with the help of a physiotherapist. 

Recovery time: 6 weeks for mild cases. More serious cases requiring physiotherapy may take up to a few months. 


6. Torn meniscus


A torn meniscus is often caused by a twisting movement of the knee while bearing weight — the force and degree of twisting can tear some of the wedge-shaped cartilage (meniscus) that provides cushioning between the thigh bone and shinbone.

Symptoms of a torn meniscus: 

  • An audible “pop” at the moment the meniscus is torn

  • Passing pain in the knee that intensifies with pressure

  • Swelling or stiffness in the knee

  • Knee feels like it is giving way or locking up with trying to bend it


  • Resting the affected knee, refraining from placing pressure on it.

  • Icing the painful area with cold packs.

  • Attending a physiotherapy session to strengthen the knee and promote better range of movement. 

Recovery time: 6-8 weeks with the help of physiotherapy. 

Causes of Sudden Knee Pain (Torn Meniscus and Arthritis)


7. Arthritis


Arthritis is an inflammatory condition that usually occurs at joints, especially the knee. Major forms of arthritis include osteoarthritis, rheumatoid arthritis, and posttraumatic arthritis. 

Symptoms of Arthritis: 

  • Pain and swelling that gets worse in the morning or after prolonged sitting or resting.

  • Pain flares after bouts of activity around the joint

  • Clicking or snapping sound when the knee is bent

  • Loss of strength in the knee joint


  • Applying cold or heat packs the painful area for temporary heat relief.

  • Targeted physiotherapy sessions to help strengthen the knee and restore movement.

Recovery time: About 6 weeks for muscles to provide sufficient support for reduced pain. Up to 3 months before being able to return to normal or sports activity. 


Diagnosing Sudden Knee Pain

This brief guide is only designed to give you a brief overview of the possible severity of the knee conditions that sudden knee pain is a symptom of. The onset of sudden knee pain is often a warning sign of a more serious injury. When the pain occurs, it’s important to immediately stop any intense activity and seek a professional medical diagnosis from a doctor or physiotherapist. 

Our team of knee pain physiotherapists at Infinite Health can help you get an accurate diagnosis of your sudden knee pain and provide you with early treatment to help you recover sooner. Book a knee physio appointment with us at our clinics across the Sydney CBD, Mosman, North Sydney, or Chatswood today!


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