Knee pain & knee injuries – what causes knee pain?

Published: June 2021
Last Reviewed: November 2024

The knee is a complex joint with many moving parts that are vulnerable to injury. Knee injuries can result from an awkward movement, a fall or collision, a sudden twist, or overuse while playing sports or exercising. Knee pain can often be instant or become progressively worse over time.

Symptoms of knee pain can vary depending on the cause, but also the severity of the injury itself. You might experience some of the following: 

• Bruising and redness, along with general knee pain
• Swelling or a warm feeling
• The knee joint might ‘lock’ or feel like it’s clicking or catching
• Knee jarring
• Inability to fully straighten the knee
• Stiffness
• A lack of strength and stability and feeling like the knee could give way 

Knee pain can occur suddenly after injury, or over time due to other factors, such as age or overuse of the knee. This can mean that knee pain can occur without any knee impact injury. Here we have identified the main reasons why you may experience some form of knee pain, as well as some less common causes and related injuries.

There are several causes of knee pain that are common for those that are particularly active, like runners, athletes and construction workers. These include:

Often occurs as injuries that happen when the ligaments in the knee joint are stretched too far or tear. Knee sprains are on of the most common knee injuries among athletes.

A common injury for runners. The IT band is the connective tissue that stretches from your hip to your knee and can become irritated and painful (on the outside of the knee) when it becomes overstretched. Building up time/distance over time and avoiding too much downhill running can ease IT band syndrome.

Occurs when a small sac at the top of your knee (Bursa) ruptures due to irritation and excessive impact. This type of injury is more common if you’re often on your knees for work (e.g. carpenters or mechanics) but can occur through excessive bending or a fall. The knee can appear warm and red.

Often caused by overuse or as part of another knee injury. Small pieces of cartilage can break loose and then become stuck within the knee joint, causing an uncomfortable sensation rather than knee pain.

The tendon that connects your kneecap to your shin bone can become inflamed from excessive exercise or jumping.

Runner's knee is officially known as patellofemoral pain syndrome and is commonly seen in people who experience knee pain after running and in other high-impact physical activities. It is a catch-all term for a range of conditions and discomforts related to the patella, kneecap or the surrounding area.

Ligament tears can occur when the ligament in the knee is overstretched or completely torn. There are four types of knee ligaments in your knee joint, including the medial collateral ligament (MCL) located on the inside edge of the knee, lateral collateral ligament (LCL) along the outside edge, anterior cruciate ligament (ACL) at the front and the posterior cruciate ligament at the back of the knee. ACL, MCL and LCL tears are more common, however you can tear or sprain any of the four ligaments.

Arthritis is a common condition that can cause joint pain, stiffness, swelling, tenderness and inability to move the joint freely. Some other potential causes of knee pain can include types of arthritis in the knee, including: 

• Osteoarthritis: This is the main cause of knee pain after the age of 50 and is the most common form of arthritis. When the protective cartilage in the knee wears down, the resulting friction can cause pain and discomfort. This can result in pain, stiffness in both knees and mild swelling. 
• Rheumatoid arthritis: This is an autoimmune condition that can impact any joint in the body, including the knees. It is the most debilitating form of arthritis and is a chronic (long-term) condition. However, it can vary in severity and usually comes and goes over time.  
• Septic arthritis: This type of arthritis occurs when the knee joint becomes infected, leading to swelling, pain, and redness. It is often accompanied by a fever, and there’s usually no trauma associated before the pain appears. Septic arthritis can cause extensive damage to the knee cartilage if left untreated. If you notice any symptoms of septic arthritis with knee pain, seek medical advice as soon as possible. 
• Gout: This type of arthritis occurs when uric acid crystals build up in the joint. Gout typically affects the big toe; however, it can also affect the knees. This can cause hot and red, sudden attacks of intense pain in the knee, like septic arthritis.

Can arthritis pain radiate down the leg?

Yes, knee pain caused by arthritis can radiate down the leg. Knee arthritis can cause significant knee pain that extends beyond the knee joint, radiating down the leg. As such, this can cause discomfort, weakness, and a tingling sensation between the knee and ankle. Knee arthritis can be debilitating and one of the symptoms can be that it radiates to other parts of the leg. 

Experiencing knee pain when bending is common among many people and can be a symptom of several underlying causes. These can include bursitis, ligament strain, tendonitis of the knee, meniscus tears and osteoarthritis. Knee pain when bending can also occur due to overuse of the knee, such as kneeling on the ground for long periods, or after an increase in physical activity. 

Knee pain can also develop from some less common causes, such as:

• Osgood-Schlatter disease: When you’re young and your knee joint is still developing you can develop this condition from overdoing it during exercise. You’ll notice a painful bump below your knee.
• Dislocated kneecap: A sudden change in direction or impact when the leg is planted can cause the kneecap dislocation, usually to the side of the knee. 

Knee injuries that weren’t properly diagnosed or treated at an earlier stage can also flair up and become painful later.

There are several potential risk factors associated with persistent knee pain. Being aware of these risk factors can help you prevent further knee pain in the future. 

• Excess weight: Being overweight or obese can increase stress and pressure on the knee joints, increasing the likelihood of experiencing knee pain. Everyday activities like walking or going up and down stairs can be extremely difficult and stressful for the knees. It can also increase your chances of developing osteoarthritis by accelerating the breakdown of joint cartilage. 
• Lack of muscle strength or flexibility: Strong muscles stabilise and protect your joints, so a lack of muscle strength in the legs can increase your chances of developing knee pain and injuries. It's also important to have flexibility in the joints, as this allows you to achieve a full range of motion. 
• Playing sports: Certain sports can increase your risk of obtaining knee injuries due to the constant movement of the knee joint. For example, sports such as alpine skiing, basketball, football and rugby all have a higher risk of causing knee pain due to the constant movement of the knee for long sustained periods. 
• Certain occupations and jobs: Some jobs that require you to be on your feet or knees for long periods of time, such as farming and construction work, can increase the risk of having knee pain.
• Previous knee injuries: If you have had a knee injury in the past, this can also increase your chances of injuring your knee again in the future.

It’s important to understand the risks of knee pain, as they can be preventable, such as increasing muscle strength and flexibility or losing excess weight to reduce stress on your knees. 

Identifying knee pain could be as simple as knowing where the pain radiates from, but the cause of knee pain or the type of knee injury is more difficult to determine, particularly if the pain isn’t as a result of a direct impact or trauma.

Knee pain and problems are diagnosed by undertaking a series of tests and examinations, such as: 

• X-ray 
• Magnetic resonance imaging (MRI) 
• Computed tomography scan (CT or CAT scan) 
• Arthroscopy  
• Radionuclide bone scan
• Physical examination of the knee affected 

For knee pain and knee injuries related to activity, like a dislocation or ligament damage, it’s important to seek medical advice as soon as possible to ensure suitable treatment can be delivered, and to reduce the risk of long-term damage.  

If your knee pain is the result of trauma, impact or obvious injury, then you should seek medical attention immediately to rule out any serious complications. 
 
If the knee pain comes and goes (for example with exercise) or isn’t too severe, then you can try some home-based treatments and products to reduce the pain and treat the injury. 

A common routine for knee pain relief is by following the RICER method, which entails the following: 

• Rest: Rest the affected knee, avoiding putting too much weight on the left, and avoid exercise for a few days to see if the pain subsides. 
  
• Ice: Apply a cold pack of frozen vegetables or ice wrapped in a towel or cloth (to avoid ice burns) for 20-25 minutes at regular intervals to help reduce inflammation and discomfort. 
  
• Compression: Gently strap the knee with a bandage. 
  
• Elevation: Elevate the injured leg and rest on a soft surface to help stop any bleeding and swelling 
• Referral: Contact a qualified physician for precise diagnosis, further testing and treatment advice. 

Some also benefit from applying contrast therapy to their knee injuries. Learn more here. 

With a Dynamic Pain Guard, the Elastoplast Protective Knee Support helps to provide support to weak or injured knees, helping to protect from further injury. It can also provide support during activities, with the ability to adjust the level of compression to your personal needs. 

For those looking for advanced flexibility, the Elastoplast Performance Knee Support is designed to provide strength, protection, compression and support to stiff, weak and painful injured knees. It provides a moderate level of support during sports and other activities. 

Learn how to wear a knee support here.

If your knee pain is the result of a more serious condition such as a dislocated knee or kneecap, damaged ligaments, bone fracture or severe arthritis, you may be recommended surgery by a doctor to treat the condition. Potential surgical options include:

• Knee arthroscopy
• Knee replacement or partial knee replacement  

These surgical options will depend on the severity of the injury and condition. Your surgeon will inform you of what to expect in terms of recovery times and how to ensure the best conditions for recovery.

Knee pain and knee injuries can be prevented, and there’s a range of steps you can take to reduce the chance of experiencing either day-to-day and in the future. 

• Wear appropriate footwear when exercising or carrying out activities 
• Wear the right protective equipment 
• Use a cane or walker for extra stability if you struggle walking or have an increased risk of falls 
• Avoid sudden or jarring movements that could result in twists or locking 
• Always warm-up and warm down appropriately after exercise 
• Work on losing weight due to reduce stress on the knees 
• Increase muscle strength through weight training to improve stability
• If you have weak knees or a history of injuries, wear appropriate supports during exercise
• Learn the proper form for activities like weightlifting, to ensure no undue pressure is put on joints and reducing the risk of knee injuries

It’s important to always seek medical attention if you notice any of the following symptoms alongside your knee pain: 

• An obvious deformity in the knee or leg 
• Have severe knee pain that is associated with a recent injury 
• Cannot straighten, fully extend or flex your knee 
• Have a fever alongside redness, pain and swelling in your knee
• Cannot place any weight onto the knee 

These symptoms may be related to more complex conditions, such as septic arthritis and gout, so it’s vital that you contact a doctor if you experience any of the above.