Causes of knee pain

Meniscal Tear ("torn cartilage")


In young adults, the meniscal cartilages are resilient and are mostly injured during sports.  A painful “pop” together with tenderness at the side of the joint may be experienced. Pain is usually aggravated by standing and deep bending. In young adults, it is often preferable to repair the torn segment of cartilage. 

As people age, the meniscus can become torn following trivial movements. Often this happens in association with arthritis. In such circumstances, surgery is usually not needed. Symtoms can usually be managed by a combination of medical treatment, physiotherapy guided rehabilitation and sometimes a joint injection.



If the joint surfaces become worn and irregular, knee movement can become stiff and painful. Osteoarthritis ("wear and tear") is more likely if the knee has been injured or had surgery in the past (such as removal of the meniscal cartilage). Often no cause is found. Treatment may vary from physiotherapy, medications, injections and knee replacement (partial or total)

Anterior Knee Pain


Pain at the front of the knee may be due to damage to the knee joint surfaces or abnormalities in the way the knee-cap guides across the femur. Sometimes inflammation in the tendons at the front of the joint may be the cause. Referred pain from the hip or spine may also be felt here. Often however, no structural abnormality is present. Usually a significant improvement can be achieved with a combination of activity modification and physiotherapy-led muscle strengthening & re-balancing. On rare occasions, surgery may be helpful.

Anterior Cruciate Ligament Rupture


The anterior cruciate ligament ("ACL") is important for knee stability and may be injured through sports.Whilst football is often thought of as a high risk activity for such injuries, more commonly these occur during non-contact play such as cutting, side-stepping or awkward landings. Usually patients usually feel something tear and are unable to continue play. The knee swells rapidly and feels unsteady. Most people will experience improvements with careful rehabilitation. Ongoing instability may prevent return to sports and reconstructive surgery may be appropriate

Joint Effusion & Bakers Cyst


In health, the knee is bathed in a small amount of joint fluid. If the knee becomes injured, worn or inflamed more fluid is produced leading to swelling and stiffness. Fluid may leak out of the back of the knee and cause a "Bakers Cyst" swelling. This may become large, painful and prevent deep knee flexion. Small collections of fluid do not need treatment though if larger, the fluid may be drained and the joint injected with steroids

Osteochondral Injury


Trauma may cause a small piece of the joint surface to be knocked off. This may also happen if the blood supply to the area is damaged ("osteochondritis dissecans"). Patients experience pain, swelling and locking. Treatments include the removal or re-attachment of the fragment. Occasionally, if the area of damage is large, cartilage repair surgery is appropriate

treating your knee without surgeryl



Exercise & Physiotherapy


Bracing & taping


Shock-wave therapy


Steroid injection


Viscoelastic Supplementation


Keyhole knee surgery (arthroscopy)


Which conditions can be treated through keyhole surgery?

A variety of conditions may be diagnosed and treated arthroscopically. Most commonly, knee arthroscopy is used to treat tears to the meniscal cartilages. Depending on the condition of the tear, the meniscus can either be trimmed ("partial meniscetomy') or repaired with stitches. Other common arthroscopic treatments include removal of loose bodies, smoothing of unstable regions of the joint surface ("chondroplasty"), articular cartilage repair ("micro-fracture"), and anterior cruciate ligament reconstruction.


What should I expect?

Surgery usually last about 25 minutes and is performed under general anaesthesia. Two small incisions (approximately 5mm length) are used to introduce the camera and instruments into the knee. Patients typically go home a few hours after the operation. Crutches are frequently not needed  (except ACL reconstruction & meniscal repair). Recovery depends on the condition of the knee and nature of the procedure. Following a trim of a small meniscal tear the knee will often feel better in a matter of days. Conversely, normal knee function will take weeks to months of rehabilitation after meniscal repair or ligament reconstruction. 

Please see further details in the "information centre". 

Partial Knee Replacement

What is a partial knee replacement?


Partial knee replacement is a conservative surgical approach to treating knee arthritis. This involves selective replacement of only the worn parts of the knee, whilst retaining the non-worn joint surfaces and all the knee ligaments.

Partial knee replacements allow treatment of isolated wear of the knee-cap joint (patello-femoral joint) or either side of the joint (medial or lateral tibio-femoral joint). In practice, these procedures involves very little bone removal and can be thought of as a "resurfacing" rather than "replacement".

Could my knee be suitable?


Approximately 1/4 of patients with knee arthritis who undergo replacement surgery could be suitable for a partial replacement. Although sometimes promoted as a better option for young and active people, partial replacement may be appropriate for adults of any age. Indeed, the less invasive nature of the surgery and easier recovery also makes  the procedure an attractive option for more elderly or less fit people.

If there is damage to the knee ligaments (ACL, PCL, or MCL), severe deformity, widespread disease or inflammatory arthritis, a full knee replacement will be more suitable.

What are the main advantages?


Compared to a total knee replacement, the recovery following a partial knee replacement is typically less painful, faster and associated with less complications. Range of motion tends to be better and patients are almost twice as likely to report that their knees feel normal. Furthermore, people with partial knee replacements are  x2.7 more likely to be satisfied with their ability to perform activities of daily living.

A detailed review of the advantages and disadvantages of partial knee replacement surgery appears in the "information centre" 

total knee replacement


Why consider a total knee replacement?

Nearly 100,000 total knee replacements are performed every year in England and Wales. Osteoarthritis remains by far the most common indication this type of surgery (96%). Other reasons include avascular necrosis, trauma and inflammatory joint disease.

It is reasonable to consider knee replacement surgery if your joint is significantly damaged and causes  problematic pain, stiffness or difficulty with activities. Before surgery, you should look at alternatives such as weight-loss, pain-killers, exercise, and perhaps joint injections.


What should I expect?

Surgery takes about an hour and most people stay in hospital for 3 nights. At first, the knee will be swollen, stiff and painful. Although we will provide a variety of strong painkillers, the first few days can be tough! Crutches are needed for 2-3 weeks. To regain good function it is important to continue to work hard with a physiotherapist during the first 6 weeks. By this stage most people are walking well and not using pain-killers. Full recovery usually takes a few months. Many patients are able to get back to an active lifestyle and can enjoy sports such as mountain-biking, hiking and swimming.


What is new in knee replacement surgery?

Total knee replacement surgery is a safe and reliable way of treating painful knee arthritis. However, some patients are not fully satisfied with the function of their artificial knees. This tends to be seen more commonly in younger and more active people. To tackle this, technologies to make surgery more accurate including robotics and custom made 3-D printed guides have been developed. Recent enhancements to 3-D printing technologies can now also allow knee replacements to be built specifically to match the patients exact shape, size, and disease pattern. Whilst such newer technologies hold great potential, these approaches are not suitable for all cases and have not been conclusively proven to be superior to established methods.

Knee replacement faqs

What is a knee replacement & what are the benefits?

During replacement surgery, the painful and worn-out part of the knee is carefully removed together with a sliver of underlying bone. In partial knee replacement surgery, most of the knee remains untouched and only the damaged area is resurfaced. In total knee replacement surgery all of the joint surfaces are replaced.These forms of surgery are appropriate to consider if there is severe pain secondary to arthritis. Knee range of motion is usually improved and if present, deformity can be corrected.  

What sort of anaesthetic will I have?

Surgery is usually performed using the combination of intravenous sedation and a low-dose spinal anaesthetic. In practice, this means that most patients will remember (but not feel) the beginning of the procedure and snooze through the rest. This approach has been shown to be both the safest and most suited to a rapid recovery program. Alternatively, a full general anaesthetic can be used. Both forms of anaesthetic are extremely safe and reliable. Whilst occasionally there is a compelling medical reason to recommend one form of anaesthesia, patient preference is usually the most important consideration. You will always be able to discuss your options with your anaesthetist beforehand.

What are the alternatives to surgery?

For many people, surgery is not required and a combination of weight loss, activity modification and occasional pain-killers may be all that is needed.  Being overweight can put a great strain on the knees and lead to premature damage. Whilst weight-loss can help ease symptoms, this is difficult when mobility is poor. For some very heavy patients, it may be sensible to consider bariatric (weight-loss) surgery. If knee arthritis is not severe, steroid injection can help to reduce discomfort for a period and allow more comfortable knee reconditioning exercises. If there is significant bowing of the knee, an “offloader” knee brace may be helpful. Some of my patients tell me that turmeric or ginger supplemnets help their symptoms though the scientific evidence for this is limited. Glucosomaine supplements do not have a role in the treatment of advanced knee arthritis.

What will happen if I don't have surgery?

Although arthritis may cause significant pain and disability, progression is quite variable. Certainly, some people find that symptoms remain stable, so for them a "watch and wait" approach is sensible. If symptoms are severe and not responding to measures as outlined above, it is often sensible not to delay surgery; if left very late, significant muscular and bone weakening can compromise the recovery.

What can I do to make the surgery a success?

It goes without saying that surgery needs to be meticulously planned and performed. Success also depends on significant effort and preparation on the part of the patient. If suffering from long-term health conditions such as diabetes, anaemia or raised blood pressure, these conditions need to be optimised before surgery. Smokers must “kick the habit” as ongoing smoking increases the risks of poor healing and post-operative chest infections. The same advice applies to alcohol intake. Losing a few pounds will make recovery easier and safer. Severe dieting before surgery must be avoided as this leads to low energy and malnutrition. Using additional multi-vitamin supplements together with iron tablets for the four weeks prior to surgery is sensible. Performing both core and knee-specific exercises (see information centre) during the four weeks before surgery will also significantly aid recovery.

What are the risks?

Knee replacement is a commonly performed procedure but should still be considered as "major" surgery.The vast majority of people will pass through their recovery without significant difficulty and be pleased with the outcome.Despite every effort to make surgery sucessful, complications can occur. The risk of a complication varies from person to person. Complications may be minor or occasionally be life changing. It is important to disucss your risk profile with your surgeon and also make sure that you understand what impact a serious complication could have on you and your family.

Recognised complications include

Risks of anaesthesia

Pain (during recovery or long-term)

Damage to nerves of major blood vessels


Post-operative nausea and vomiting



Thrombosis & embolism

Failure requiring further surgery




Whilst it is appropriate for a patient to be aware of both what to expect and what could go wrong including the worst-case scenario, it must be stressed that the great majority of patients do not suffer any such complications!

preparing for surgery

Learn what you can do before surgery to help make your recovery as smooth as possible.

Failed knee replacement (revision surgery)

painful total knee

Why do some knee replacements fail?

Knee replacement is generally a very reliable and successful operation. Every year in the U.K, this procedure allows thousands of adults to return to more active and pain-free lifestyles. Mostly, a new knee will be a once in a lifetime operation. However, as with all mechanical devices, knee replacements can fail. If this occurs, it is hugely disappointing for the patient and revision surgery may be needed.

The class of knee replacement most frequently used by Mr Bartlett  (termed; “cemented, unconstrained, fixed bearing total knee replacement”) shows the best overall survivorship (about 5% chance of revision at 10 years). By contrast, after a partial knee replacement, further surgery is required at over twice this rate.

The most common reason for partial knees to need further surgery is the progression of arthritis elsewhere in the joint. Usually, this is treated by a relatively straightforward conversion to total knee replacement. Although relatively uncommon, loosening is the most frequent indication for revision of total knee replacements. Other causes include infection, stiffness, instability, implant fracture/ dislocation or persistent pain.

Younger patients are at increased risk of needing revision surgery. There are a variety of reasons to explain this observation (disease profile, level of activity, threshold to surgery in the elderly). The bottom line is that patients under 60 years of age can still greatly benefit from knee replacement surgery but should only proceed after thoroghly exploring other options first. Surgeon experience and implant choice also influence long-term success.

SPECT CT Scan indicating femoral component looseing

Investigations for a painful knee replacement

Many causes of knee pain after replacement surgery will respond to simple measures like physiotherapy or an injection. In other cases, the symptoms may not be due to the knee at all (for instance caused by hip arthritis).

Occasionally, the cause of pain may be due to an obvious problem with a knee replacement (e.g. fracture or acute infection). More commonly, the issue can only be understood after detailed and un-rushed evaluation. 

Assessment initially requires a careful discussion going back to the beginning of problems with the joint. This, together with a thorough examination, blood tests and X-rays will frequently yield the diagnosis. If uncertainly remains, further investigations are required to determine if there is infection, loosening,  malalignment or instability. Specialised scans (SPECT CT or occasionally MRI) are often helpful. Sometimes it is also necessary to assess the knee in the operating theatre and under anaesthetic. This allows evaluation of the mechanical functioning of the joint, collection of tissue for microbiological analysis and direct inspection of the joint using a keyhole a camera.


Revision knee replacement surgery

Although it is sometimes possible to adjust just one part of the replacement, in most cases all the original components are all removed. As the bone and ligaments around the joint are usually damaged, the challenge is to reconstruct the knee so that it is stable and has near normal movement. Although recent advances to specialist revision systems greatly facilitate this, surgery remains technically demanding. 

If a revision procedure is being performed for the treatment of an infected knee replacement, surgery may need to be performed in two stages (intial removal of the infected replacement and insertion of a tempory antibiotic loaded spacer followed by definitve reconstruction once the infection is fully cleared). Recovery tends to be a slower than after a primary knee replacement and the risks are increased. Although this form of surgery aims to correct specific problems and improve function, the results are not usually as good as a successful “first time around” knee replacement. Every case is different and it is critical for each patient has realistic expectations about what can be achieved.

custom knee replacement

The Conformis custom total knee replacement is custom built to perfectly fit each patient. Early results suggest improved patient satisfaction and knee movement but superiority over conventional knee replacement is not yet proven...