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Knee pain

Find out the causes of knee pain and how it can be treated.

Doctor examining patients knee joint weeks following surgery
In the vast majority of cases, knee pain is a result of biomechanical factors, degenerative joint processes or traumatic injuries to the knee (which can often cause sudden knee pain).

If you’re experiencing knee pain and asking questions such as:

  • How do I know if my knee pain is serious?
  • What causes pain in knees without injury?
  • What is the most common cause of knee pain?
  • How can I relieve pain in my knee?

this guide will offer you some pointers around the causes and how to help with chronic knee pain. It will also offer you some handy tips on how to stay active with knee joint pain, or a knee injury or condition.

Our trained Consultants and knee specialists are also available to discuss your condition in more detail and recommend an appropriate knee pain treatment for you.

The knee is the largest and strongest joint in the body. It is made up of several components: 

  • The lower end of the thigh-bone (femur)
  • The upper end of the shin-bone (tibia)
  • The kneecap (patella) 

The ends of the bones in the knee joint are covered with articular cartilage. This is a smooth material that cushions the bones during movement. Two crescent-shaped structures made out of cartilage, called the lateral meniscus and medial meniscus, sit between the thigh-bone and shin-bone. This rubbery material helps to cushion the joint and keep it stable.  

A thin lining, called the synovial membrane, surrounds the joint. It helps to lubricate the cartilage and reduce friction.  

Due to its location in the body and the demands placed upon it by normal daily life, the knee joint is a common place to feel pain or suffer injury. The basic function of the joint is to allow movement of the leg in a front to back direction. 

However, the knee is in fact a modified hinge joint that allows some rotation. This is needed for two reasons.  

First, this rotation allows the knee a degree of extra mobility when performing tasks such as squatting and jogging, especially when changing direction simultaneously. This is essential for the type of movements needed when playing sports. 

Second, this small amount of rotation allows the knee joint to be able to lock when fully straight (full extension). You may feel the benefit of this with a healthy knee in standing if you tense your knee muscles to fully straighten your knee. This allows us to stand in a stable position with less effort. 

The other unique aspect to the knee is the addition of the kneecap (patella) to the joint anatomy. The patella is present to protect the front of the knee joint when kneeling or if it is struck. However, the other key function of the kneecap is to act as an interim lever to attach the large muscles at the front of the thigh (quadriceps muscles) to the top of the lower leg bone (tibia). 

This lever action provides a great deal more force for the quadriceps muscles, which are the main stabiliser and mover of the knee joint during functional tasks. Research has demonstrated that this system increases the quadriceps effectiveness by more than 200% at some angles of knee flexion. 

Although the knee is a remarkable joint and has adapted to the demands placed upon it, it is still subject to huge forces.

When something goes wrong with the knee, it results in knee joint pain. This may be felt as an inside knee pain or as knee pain after running. 

There are two main causes of knee problems, traumatic and overuse/degenerative. 

One example of overuse in daily life is the amount of bodyweight that goes through the knee joint during normal daily activities, such as: 

  • Cycling: 1.2 times the body-weight 
  • Walking: 3 times the body-weight 
  • Climbing stairs: 4-5 times the body-weight 
  • Squatting down: 5-6 times the body-weight 

The kneecap joint (patellofemoral joint) also experiences huge compression forces during everyday tasks, such as: 

  • Cycling: 1-2 times the body-weight 
  • Walking: 1-2 times the body-weight 
  • Climbing stairs: 5 times the body-weight 
  • Squatting down: 7 times the body-weight 

These tasks are performed many times each day, so even with the knee joints design to withstand such forces, it is no surprise that the knee joint suffers from an overuse and degenerative pain disorders. 

The other factor to consider is the site of the knee located between the ankle and foot, which are often fixed to the ground, and the hip, which allows significant amounts of rotation.  

When playing sports, many acute knee injuries are the result of the knee being unable to cope with the rotation placed upon it with the foot fixed to the floor. This can be compounded with the use of studded footwear, which does not allow the foot to pivot. 

Other sports-related traumatic knee injuries can occur as a result of a direct impact to the knee by an opponent at an awkward angle. Common examples are being tackled when playing football or direct clashes during heavy contact sports, such as rugby. 

The symptoms of knee pain are split into two broad categories, which should help with knee pain diagnosis.

Those that are caused by a traumatic injury to the knee, and those that are caused by overuse or a degenerative injury to the knee. 

Traumatic injuries to the knee

The most common form of traumatic knee injury is a tear to one of the menisci. These act as shock absorbers between the joint surfaces and due to the extreme loads placed upon the knee joint during sports they are prone to injury. 

Of the two, the medial meniscus is much more commonly injured than the lateral meniscus. This is because it is attached to other structures on the inside of the knee, which makes it vulnerable when these structures are tensioned. 

The common cause of injury is when a sports player turns direction and catches their foot awkwardly in the turf or when the knee buckles on landing awkwardly such as when playing football, netball or basketball.

Pain on the outside of the knee is a common symptom of this type of injury. Other less common but troubling causes of traumatic knee pain are knee ligament injuries.

There are four ligaments around the knee: 

  • Anterior cruciate ligament 
  • Posterior cruciate ligament 
  • Medial collateral ligament 
  • Lateral collateral ligament 

Because these structures are closely linked, it is possible to get a meniscal tear and damage the anterior cruciate ligament at the same time.

When this happens, it is called a medial collateral ligament. Inner knee pain is a common symptom of this type of injury.  Isolated medial collateral ligament injuries normally occur as a result of inwards impact to the outer side of the knee, such as from an opponent during contact sports.

This forces the knee to deviate inwards and overload the medial collateral ligament, which lies on the inside of the knee. Pain on inner side of knee is a common symptom of this type of injury.  Depending on which traumatic injury you have sustained, the location and severity of knee pain may vary.

Symptoms that accompany knee pain include: 

  • Swelling and stiffness 
  • Redness around the knee, and it feels warm to the touch 
  • Weakness or instability in the knee joint 
  • Popping or crunching noises 
  • Inability to fully straighten the knee 

Overuse/degenerative injuries to the knee

Early age-related changes known as osteoarthritis is the most common form of knee pain in middle-aged and elderly individuals. Knee pain when bending and knee pain when walking are both common symptoms that there is something wrong with the knee.  

Knee pain due to osteoarthritis is characterised with pain and sometimes intermittent periods of swelling and instability to the knee. The process of osteoarthritis involves a gradual wearing and thinning of cartilage in the joint surfaces as well as a stiffening of the soft tissue within and around the knee joint. 

Most commonly, this process affects mainly the inside of the knee known as the medial compartment but can occur in the outer (lateral) knee compartment or the patella-femoral joint simultaneously.  Age-related changes to the menisci of the knee also occur.

These may occur in conjunction with more diffuse knee osteoarthritis or independently. These age-related changes can manifest in cysts developing to the edges of the menisci or degenerative tears to the menisci in the absence of any undue trauma. 

Sports that involve a lot of straight line running with little side to side or rotational movements can cause knee pain in the kneecap (patellofemoral joint). You may experience back of knee pain or pain behind knee if you are overusing your knee joint. 

It is thought that the absence of lateral movements may lead to muscle imbalances at the hip and knee. This in turn increases the load through the patellofemoral joint, which can lead to excessive friction developing on the outer aspect of the knee. 

The symptoms of a degenerative condition depend upon the type of arthritis. These symptoms may gradually progress as your condition worsens. However, it is possible that a minor injury will cause the symptoms to worsen. 

The most common symptoms of knee arthritis include: 

  • Pain when doing an activity, such as walking up or down stairs 
  • Limited range of motion in the leg 
  • Stiffness   
  • Swelling   
  • Tenderness around the knee 
  • A weakness or instability feeling in the knee 
  • Existing deformity of the joint, such as knock-knees or bow-legs 

Knee arthritis pain is usually worse after doing an activity, especially with overuse. Your knee may also feel stiff if you have being sitting for a long period. 

Often knee pain will be short-term and caused by overuse or by a small injury caused by twisting or knocking your knee.

Try resting your knee for a few days or placing a soft pillow between your knees whilst sleeping if you prefer to sleep on your side.

If the pain doesn't ease or go away, speak to your GP who will help you get a diagnosis.

If it feels more serious or you want a second opinion, then our trained Consultants and knee experts can help.

Osteoarthritis of the knee

Many people don't realise that the term arthritis can be used to describe most conditions where there's pain and inflammation in a joint. Arthritis is a condition that can affect any joint, and the knee joint is one of the most commonly afflicted.

There are two forms of arthritis, one of which is from general wear and tear of the bones. This is called osteoarthritis, and the more wear your bones get, the more painful they become, including to the point that you can no longer walk unaided.

Osteoarthritis is not curable, but you can still live a comfortable life if you're suffering from its effects on your knee bones thanks to modern knee replacement surgery.

Robotic arms can also be used to aid this type of surgery and can greatly improve the outcome by ensuring a better fit during prosthetic knee replacement surgery.

Rheumatoid arthritis of the knee

The other major form of arthritis is rheumatoid arthritis. Like all forms of arthritis this can affect any joint in the body, but is most common in the hands and feet. However, it can and does affect knee joints too, and can cause severe problems and pain if not treated.

The fluid that helps keep our knees working efficiently is called synovial fluid. This is produced from the synovial membrane that surrounds the knee joints.

Rheumatoid arthritis is an immune deficiency disorder, which attacks tissue in the body. In the case of the knee, the target is the synovial membrane, and when that happens, inflammation causes the membrane to swell, which then limits movement of the knee as well as causing pain.

This can lead to damage of other parts of the knee including the bones, cartilage, and ligaments, at which point urgent treatment will be needed.


As well as cartilage and the menisci to reduce friction and absorb shocks from the more strenuous activities we put out knee joints through, the knee also contains a number of small sacs of fluid called bursae.

These reduce friction in areas of the knee including the movement of ligaments and the patella, and can become inflamed and cause pain.

Even something as simple as kneeling for an extended period of time can cause problems to a bursa, but they can also become infected or inflamed by bacteria, gout, or arthritis.

The medical name for problems with the bursa sacs is bursitis and should be investigated if the pain does not go away after a few days in case there are any extenuating circumstances.

Patellar Tendonitis

This injury is caused by overuse of the knee. It normally causes pain in the front of the knee and is sometimes called jumper's knee (the term refers to athletes who can suffer from this condition due to excessive training).

It happens when tiny tears in the tendons that hold the patella in place begin to form. If these tears are not allowed to heal, they will worsen. This is called tendinopathy, which increases the swelling around the knee causing further pain.

Anterior cruciate ligament (ACL) injury

This is the most common knee ligament injury, which is also frequently suffered by athletes. It can make your knee unstable and will usually need treatment.

It's one of the strongest ligaments in the knee joint, connecting the femur to the tibia, so as you can imagine, if this tears or ruptures, it not only causes severe pain, but can debilitate movement completely.

Torn meniscus

The menisci play an important part in absorbing shocks to the knee and thigh bone as we know, but they also help regulate the stability of our knees and provide lubrication and nutrients to the knee joint.

The term meniscus comes from the Greek and translates as 'crescent', which is more or less the shape of these two important parts of the knee. They are made up mostly of water (72%) and collagen (22%).

If we make a sudden turn, whilst playing sport for example, it's possible to tear either or both of the menisci, which results in swelling and stiffness along with pain, especially when trying to do anything involving movement of the knee (twisting or extending the leg).

Whilst it's possible for minor meniscus tears to naturally heal over time given enough rest and pain relief treatment, in more extreme cases, surgery may be required.

Runner's knee

Runner's knee is a loose term covering a number of different conditions usually affecting the kneecap or patella and the tissue surrounding it. The most common of these conditions is called patellofemoral pain syndrome (PFPS).

Other associated terms you may hear include 'anterior knee pain', 'iliotibial band syndrome' (ITBS), and chondromalacia patella (the breakdown of cartilage behind the kneecap).

Runner's knee occurs when too much stress or shock is repeatedly put on the knee, such as when running on hard surfaces like roads or pavements or when performing squats with heavy weights, but it can also happen suddenly from direct trauma to the knee.

You'll know if you have runner's knee (or a related injury) because the first symptom you'll feel is pain in or around the kneecap, however if it persists despite rest, then it's a good idea to have it checked out by a knee specialist to make sure it's nothing more serious.

Baker's cyst (pain or lump in the back of the knee)

A cyst is a fluid filled sac that can form more or less anywhere in the body including the knee. There are primary cysts, which form without any underlying conditions, and there are secondary cysts which happen because of underlying conditions.

In the case of the knee, Baker's cyst is a secondary cyst formed by leakage of synovial fluid from the cartilage in the knee joint (from a torn meniscus or a bursa for example).

Baker's cyst happens when the fluid leaks into the popliteal space at the back of the knee (it's other name is popliteal cyst), resulting in a visible bulge and swelling, which can become quite painful depending on the severity of the trauma.

Baker's cyst was named after the 19th century physician, William Morrant Baker

Gout of the knee

Although most people think of gout as being a foot (and in particular, big toe) disease, it can and does affect other joints, including the knee.

Gout is a build up of uric acid that forms into small needle-like crystals within a joint. This build up then causes inflammation with increasing pain. In the worst cases, this can be debilitating and last from days to weeks.

As the crystals build up over time, they form into extremely painful nodules called tophi, which can affect movement of the joint too.

Uric acid is a waste product in the blood created from the breakdown of purines found in many food types. The kidneys usually deal with it as they clean the blood by extracting it and passing it out through our urinary system.

If the kidneys are unable to cope with excess uric, gout then becomes a possibility.

Dislocation of the knee

In severe accidents, the femur and tibia can become dislocated at the knee joint. This can result in extreme trauma, and surgery will be necessary to restore movement back to the knee.

Dislocation of just the kneecap is more common though. This is where the kneecap slips out of its groove at the lower end of the femur. That can happen if the cartilage and muscles around the knee become weakened or through an injury.

Whilst the above list of causes of knee pain cover most conditions, it's by no means all.

Fractures, strains, bruising, viruses, along with other diseases all play a part in the cause of knee pain, but to get the full picture, we also need to take into account things like our environment.

For example, the temperature can play a part, particularly during cold weather such as the winter months.

Pain in the back of the knee

Baker's cyst is an obvious contender for conditions that cause pain in the back of our knees, but there are many other possibilities, most of which are more common.

Gout can affect all parts of the knee as well as the back of the knee, as can damage to the ligaments and muscles. There is even something called pseudogout, which is similar to gout, but is the formation of crystals of calcium pyrophosphate as opposed to ural acid crystals.

Joint infections such as septic arthritis can cause severe pain anywhere in the knee including the back of the knee as can pulling a hamstring, and the pain from both of these can come on suddenly as well.

That's why it's important to see a specialist knee consultant sooner rather than later if you're in any way worried about it, or if your knee pain starts affecting your quality of life.

Once the causes of your knee pain have been diagnosed, your knee Consultant will work with you on a treatment plan that's best for your individual circumstances.

Mr Bobby Anand is a consultant orthopaedic surgeon at Shirley Oaks Hospital. He explains what injuries and conditions can lead to knee pain.

"Knee pain can occur for many reasons. An injury might damage the cartilage, the meniscus, the ligaments or the tendons of the knee.

There are also many common conditions that can cause pain in the knee. For example, the knee can wear out over time and this can lead to osteoarthritis.

The most common symptom of knee damage is knee pain itself. The pain can be very varied. Often the level and type of pain can give us an idea of the type of problem that's occurring.

Swelling is another symptom. If the knee starts swelling up, it's a sign that there's something in the joint that's irritating it; it's your body's way of telling you there's something wrong with your knee.

The three most common problems that I tend to see are:

  • Tears to the meniscus
  • Damaged or torn ligaments, in particular the anterior cruciate ligament (ACL)
  • Osteoarthritis of the knee

When should I seek help for knee pain?

If you develop pain in your knee, try resting it for a few days. You can also use an ice pack and/or use mild over-the-counter painkillers. Your local pharmacist will be able to give you advice on these options.

If your pain and swelling persist after this, it's best to speak to your GP, a physiotherapist, or a specialist consultant. They'll help you identify what's wrong.

Most knee pain is not caused by anything serious, however it is still best to get it checked out sooner rather than later in case you need a particular treatment or a prolonged period of rest.

What treatments are available for knee pain?

The type of treatment you are recommended for your knee pain will depend on the cause as well as the severity of your symptoms.

For example, if you have an injury, you may be given a recovery plan that will help you get back to normal as soon as possible. If your pain is due to mild wear and tear, the first step may be to build strength in the muscles around the joint with exercise.

If you have very advanced osteoarthritis, you may be recommended more invasive treatments such as surgery.

Certain lifestyle factors can increase the risk of knee pain. Making small lifestyle changes to improve your health will most likely be the first advice you are given to try and reduce or even cure your knee pain.

For example, losing weight can ease the pressure on your knees, while non-strenuous exercise can help strengthen the muscles around your joints and increase synovial fluid production that lubricates your knee.

Making small changes like this can significantly reduce your pain in the long term, and even stop you from needing more invasive treatments in the future.

Non-surgical knee pain treatment

Sometimes you will need a little more than lifestyle changes to get your knee pain under control. There are various non-surgical treatments you may be prescribed.

Your consultant might first recommend physical therapy. A physiotherapist will show you movements and exercises that can reduce pain and improve flexibility without further damaging your knee.

There are also medications that might be recommended. These include painkillers (both over the counter and prescription), anti-inflammatories and joint injections.

Surgery will only be recommended if you and your consultant both think it's the best choice for you.

There are many different types of knee surgery available. The one you are recommended will depend on what condition is affecting your knee, as well as your personal circumstances.

For example, procedures to repair a torn anterior cruciate ligament or meniscus are quite common after these injuries, which can't always heal on their own.

If you have very advanced arthritis and your pain or lack of mobility is stopping you from doing the things you love, you might be recommended knee replacement surgery. This involves removing part or all of your damaged knee joint and replacing it with a prosthesis.

Knee replacement surgery can have huge benefits to a person's quality of life, but it won't be recommended unless you've tried less invasive methods and they haven't worked.

If you would like to speak to one of our private specialist Consultant orthopaedic knee surgeons, please get in touch. You can find your nearest Circle Health Group private hospital using the search facilities on this site, or by calling us at the number at the top of this page.

We look forward to speaking with you and hope that we can help improve your quality of life by getting you back on the road to recovery as soon as possible.

Specialists offering Knee pain

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Mr Rishi Chana

Consultant Hip and Knee Orthopaedic Surgeon

MBBS, BSc (Hons), MRCS Ed, MSc (Dist), PG Med Ed, FRCS Tr&Orth Ed

The Chiltern Hospital 1 more The Princess Margaret Hospital

View profile Book online

Mr Aniruddha Pendse

Consultant Traume & Orthopaedic Surgeon

MBBS, MS (Tr & Orth), MRCS, MSc (Tr & Orth), FRCS (Tr & Orth), PG Dip (Health services and Management)

The Chiltern Hospital 1 more The Shelburne Hospital

View profile Book online

Mr Bhupinder Singh Mann

Consultant Orthopaedic Surgeon

BSc, MBBS, MRCS, FRCS, (Tr. & Orth.)

The Chiltern Hospital 1 more The Shelburne Hospital

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Mr Parm Johal

Consultant Orthopaedic Surgeon

MBBS, MD, FRCS(Tr & Orth)

The Chiltern Hospital

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Mr David Johnstone

Consultant Orthopaedic Surgeon

MBBS, FRCS England, FRCS (Orth.)

The Chiltern Hospital

View profile Book online

Mr Nick Beattie

Consultant Orthopaedic Surgeon

BSc (Hons.), MBCHB, MRCS, FRCS(Ed) T+O, PG Cert Ed

The Chiltern Hospital 1 more The Shelburne Hospital

View profile Book online

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