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What Are The Red Flags For Knee Pain? When To Seek Help

Read time: 6 mins

Person holding their knee in pain. Knee Pain red flags

If you’re experiencing sudden or persistent knee pain, it may be time to consult a specialist. Whether it’s a sharp, unexpected pain or a dull ache that refuses to subside, your discomfort could signal an underlying issue that requires medical attention. Early evaluation is crucial not only for identifying the cause of your pain—be it an injury, arthritis, or overuse—but also for addressing it before it escalates into something more serious.

We spoke to Mr Parag Jaiswal, Consultant Orthopaedic & Trauma Surgeon about the red flags of knee pain. Mr Jaiswal is a Hip & Knee surgeon based at St John & St Elizabeth Hospital with a specialism in complex knee surgeries.

Common Causes of Knee Pain

Knee pain can arise from various conditions, including:

Acute Knee Injuries

Trauma to the knee can result in injuries such as ligament tears (ACL, MCL, PCL, or LCL), fractures, or damage to the meniscus. These injuries often occur during sports, accidents, or falls and can lead to instability, swelling, and sharp pain. Without prompt treatment, such injuries may worsen and affect long-term joint function.

For patients with knee injuries, tools like the ‘Ottawa Knee Rule’ can guide healthcare providers in deciding if imaging is needed to assess the severity of the injury.

Overuse Syndromes

Repetitive strain on the knee joint can lead to conditions like tendinitis or bursitis. Tendinitis occurs when the tendons that connect muscle to bone become inflamed, often due to repetitive motion or high-impact activities.

Bursitis, an inflammation of the fluid-filled sacs (bursae) that cushion the knee joint, can develop from prolonged kneeling or overuse. Both conditions can cause discomfort, swelling, and limited movement.

Arthritis

Arthritis, particularly osteoarthritis (OA), is a common cause of knee pain, especially in older adults. A Versus Arthritis UK data report states that:

  • An estimated 10 million people (6 million women, 4 million men) in the UK have OA, with 5.4 million affected by knee OA and 3.2 million by hip OA.
  • An estimated 350,000 people are diagnosed with OA each year.
  • The median (average) age of symptom onset is 55 years.

In addition to OA, rheumatoid arthritis (an autoimmune, inflammatory condition) and gout (caused by uric acid crystal deposits) can lead to significant knee pain, swelling, and stiffness.

Infections

Septic arthritis or infections within the joint can cause sudden, intense pain, redness, and swelling. These conditions require immediate medical attention to prevent joint damage or the spread of infection.

Fever, significant loss of range of movement and an inability to bear weight on the affected leg are common indicators of an infection.

Underlying Multiple Chronic Medical Conditions

Systemic conditions like lupus, fibromyalgia, or thyroid disorders can sometimes cause knee pain by affecting the joints and nearby tissues. These conditions often come with other symptoms, like fatigue, widespread pain, or muscle weakness.

For patients with multiple chronic health issues, a careful evaluation is essential to spot any concerning signs and ensure the right treatment approach.

The Warning Signs of Knee Pain

While some knee pain may resolve with rest and self-care, certain symptoms require immediate medical attention.

Spotting warning signs early is key to understanding serious medical conditions and making sure patients get the right care quickly.

Sudden Severe Pain

This could indicate a fracture, ligament tear, or dislocation, especially after recent knee injury.

Swelling and Warmth

Rapid swelling and a warm sensation might signal an infection or acute inflammation.

Rapid swelling and warmth in the calf could be signs of deep vein thrombosis (DVT), a serious condition that needs prompt attention to avoid complications.

Knee Locking

Difficulty straightening the knee can be due to meniscal tears or loose bodies in the joint.

Persistent Pain

Ongoing discomfort that doesn’t improve with rest may be linked to chronic conditions or structural damage. Episodes of pain after exertion (walking or stair climbing) can also be a red flag for peripheral vascular disease, necessitating immediate medical evaluation.

Knee Buckling

Episodes of instability can suggest ligament and/or meniscus injury or nerve-related issues.

Consistent Pain After Surgery

Unresolved pain following knee surgery warrants further investigation to rule out complications.

When Should You Seek Advice or Consultation?

Physical Therapy

Mild to moderate knee pain caused by overuse or minor injuries can often be managed with physiotherapy. Our specialists develop tailored plans to strengthen muscles, improve mobility, and alleviate discomfort. Our physical therapy services provide direct access to care, allowing for comprehensive examinations and tailored treatment plans.

Surgery

Severe pain, instability, or structural damage may require surgical intervention. Our expert orthopaedic surgeons will guide you through the options, ensuring you receive the best care for your needs.

Types of Knee Surgery Available at St John & St Elizabeth Hospital

Knee Arthroscopy

Minimally invasive surgery to diagnose and treat joint issues.

ACL Reconstruction

Repair of anterior cruciate ligament injuries.

LCL Reconstruction

Surgery for lateral collateral ligament tears.

Meniscal Surgery

Removal or repair of damaged meniscus tissue.

PCL Reconstruction

Posterior cruciate ligament repair.

Knee Replacement Surgery

Total or partial replacement for severe arthritis or injury.

Excision of Bursa

Removal of inflamed bursa tissue to reduce pain.

Arthrosamid Injections

Non-surgical option to manage chronic knee pain, usually of osteoarthritis

When to Take Action for Knee Pain

Knee pain can range from a minor inconvenience to a sign of a more serious issue. Understanding the red flags—such as sudden severe pain, persistent discomfort, or swelling and warmth—can help you decide when to seek professional advice. Acting quickly can prevent further complications and lead to a more effective treatment plan.

At St John & St Elizabeth Hospital, we’re committed to providing compassionate, expert care tailored to your needs. Whether it’s physiotherapy for minor injuries or advanced surgical solutions for more severe conditions, our experienced team is here to support you every step.

Our hospital in St John’s Wood (NW8) is home to a team of experienced knee specialists and physiotherapists. With state-of-the-art facilities and a patient-centred approach, we’re here to support your recovery journey.

Posted on: 25 September 2025

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