Knee osteoarthritis (OA) is one of the most common chronic musculoskeletal conditions seen by physiotherapists and affects a large number of Australians. It is generally considered a degenerative condition (occurs via wear and tear). OA is a condition in which the hyaline articular cartilage thins, develops cracks and can eventually wear away.
Tell me more about knee osteoarthritis.
Hyaline articular cartilage is a special type of tissue that coats the ends of the bones located inside joints. In the knee, articular cartilage covers the ends of the femur and tibia, and the back of the patella along with its groove. It is made of cartilage cells (chondrocytes), collagen, water and various proteins. Its role is to provide a smooth, friction-free surface to allow the joint to glide, while protecting and helping transmit load to the underlying bone (subchondral bone).
OA is a condition in which the hyaline articular cartilage thins, develops cracks and can eventually wear away. This can result in a rough joint surface and reduce the cartilage’s ability to protect the subchondral bone. However, OA doesn’t just affect the joint cartilage. As OA progresses, bone spurs can form in the joint, the subchondral bone can form cysts and the menisci (washer-type cartilages within the knee joint) often develop degenerative tears. The layer of tissue that surrounds the inside of the knee joint (synovium) can also become inflamed and increase production of joint fluid, leading to swelling. All of these changes are thought to contribute to the pain and various other symptoms of knee OA.
What causes knee osteoarthritis?
The articular cartilage of the knee is kept healthy by movement and load. OA develops when the articular cartilage is either exposed to higher loads than it can withstand, often over a long period of time, or when the cartilage itself isn’t able to withstand relatively normal loads. Knee OA is therefore caused by a variety of factors. These include:
Though knee OA can affect younger people, it is significantly more common with each decade above the age of 45.
Being overweight increases the risk of knee OA, as well as the likelihood of it progressing. This is because the knee is a load bearing joint and as such, loads on the articular cartilage of the knee are relative to body weight.
Before the age of 50, men have slightly higher rates of knee OA, but after the age of 50, the rates are higher in women.
Past history of trauma or surgery to the knee (eg, ligament reconstruction)
This may lead a person to develop knee OA at an earlier age than average due to specific damage to the cartilage at the time of injury, or the strength and stability able to be regained in the knee after an injury.
Family history of knee OA
Some people may have inherited a form of articular cartilage that is less robust than average, reducing its ability to withstand load over time.
Heavily physical occupations
These can place a lot of load on the knees over many years.
Natural leg posture
For example, in a person with ‘bow legs’ the inner aspect (medial compartment) of the knee will bear more load than the outer aspect (lateral compartment). This load accumulates over the years and can cause early wear and tear of the cartilage in the medial compartment of the joint.
For example, in a person with long-term patella (kneecap) maltracking, the repeated rubbing of the patella against its groove can cause early wear and tear to the articular surfaces of the patellofemoral joint.
Especially in the quadriceps (front of thigh) muscles can contribute to increased loads being placed on the joint surfaces.
How do I know if I have knee osteoarthritis?
Knee OA has a variety of symptoms that are related to the main site of OA within the knee, the severity of the OA, the amount of strength and control a person has around their knee, as well as any other conditions present within the knee (eg, a meniscal tear). It is a diagnosis made according to a person’s symptoms and their examination findings.
Symptoms commonly include:
Knee OA symptoms commonly fluctuate, sometimes being better or worse, depending on activity. The symptoms may initially only be with activity but as OA progresses, knee pain may be experienced at rest or during the night.
Imaging techniques such as X-ray and MRI also play a role in diagnosing knee OA, though it is important to note that knee symptoms may not always match the imaging findings. Some people have quite troubling knee symptoms without much change on X-ray, whereas some people may have findings of advanced OA on their scans, though not be troubled much by pain. Treatment is dictated more by the individual person’s symptoms than their scans.
How can physiotherapy help with knee osteoarthritis?
Physiotherapy can help people with knee OA in many ways. Some physiotherapy management options are common to all people with knee OA, though many are specific to an individual’s type of knee OA, their contributing factors and their lifestyle. Things your physiotherapist can help you with include:
Education about OA
There is evidence to suggest that understanding the condition of OA helps with pain control, coping and ongoing symptom management. It helps a person be an active participant in their knee condition.
Prescribing an exercise program
Physiotherapists can tailor a program to help strengthen the muscles around the knee and improve how a person controls their knee position. This is very important, as people with knee OA commonly have significantly reduced quadriceps strength. Leg weakness results in further limitation to a person being able to continue daily activity and is linked with the progression of knee OA. Your physiotherapist is an expert in exercise prescription and, hence, can teach safe, effective forms of strength exercise for people with knee OA in ways that don’t provoke pain. Physiotherapy-prescribed exercise may also delay the need for knee replacement surgery.
Teaching strategies to allow a person with knee OA to stay active and keep participating in their daily tasks.
Advice regarding weight control
This can include exercise options, such as swimming or bike riding for maintaining healthy weight if walking is painful for a person with knee OA. The OsteoArthritis Research Society International has found that the most-effective conservative treatment for knee OA in people who are overweight is weight-loss.
Physiotherapists can discuss options for bracing and footwear that may help with knee OA symptoms. For example, some people with mainly patellofemoral OA may find forms of taping helpful, whereas those with mainly medial compartment OA may find types of offloading braces (or orthotics) useful.
Techniques such as massage may form part of a treatment program if a person has restricted flexibility in their knee (or hip or ankle) that might be placing increased stress on their knee joint.
Heat or cold
Your physiotherapist can discuss whether using heat or cold packs might provide you with some symptom relief.
Physiotherapists commonly work as part of a team including GPs, surgeons, psychologists, pharmacists, dieticians, sports doctors and surgeons. In this team setting, communication regarding a patient’s progress with knee OA treatment may include whether additional medications or specific dietary advice may be beneficial.
If a person’s OA progresses to the point of needing total knee replacement surgery, physiotherapy-led prehabilitation (a form of specific exercise training and education prior to surgery) has been shown to help patients enter surgery better prepared and recover faster.
If a person with OA does eventually need total knee replacement surgery, physiotherapists are experts in providing post-operative rehabilitation to get a person back to their best level of function.
How effective is physiotherapy for treating knee osteoarthritis?
There is good evidence to support physiotherapy management of knee OA. The main areas supported by research include:
Physiotherapy vs arthroscopy for knee OA: physiotherapy exercise and education, combined with standard medical care (simple pain medication) is equally effective to keyhole knee surgery (arthroscopy) in the management of knee OA. In people with moderate to severe knee OA, it has been found that arthroscopy added no additional benefit in terms of physical function, pain or quality of life, when compared to physiotherapy and simple medication. In addition, physiotherapy has been shown to have minimal risk of negative side effects compared to surgery.
Supervised physiotherapy exercise programs: for example, Good Life with Osteoarthritis in Denmark (GLA:D) research looked at a group of people with knee OA undertaking two sessions of control, stability and strength exercise per week for six weeks, plus three sessions of education regarding knee OA. The results included: participants needing less sick leave from work for knee pain, and reducing their use of pain medications; participants increasing their physical activity at three months and 12 months after finishing the program; participants continuing to experience a 31 per cent pain reduction at three months and a 36 per cent pain reduction at 12 months post-program respectively; 94 per cent of participants enjoyed the program and very few experienced pain flare-ups, none to the point of needing to stop training; and there was a significant improvement in knee-related quality of life and the majority of participants report using their new skills daily. This program is now available in Australia.
Prehabilitation: various studies have looked at programs of strength, movement control and cardiovascular exercise for 6–8 weeks prior to total knee replacement surgery. Most studies have found improvements in post-operative pain and function in the few months following surgery, and some have shown reductions in length of hospital stay. Some of the main reasons for these outcomes include patients entering surgery with a better baseline of physical conditioning and better mental preparedness.
What can I do at home?
It is also important that an exercise program for knee OA not cause a significant increase in knee pain while doing or following the exercises. In order to keep your knee comfortable, and to get the best results from an exercise program, particular attention to technique, leg positioning, amount of weight and range of knee movement may be required.
An exercise program for knee OA should contain a mixture of the following:
Cardiovascular exercise: this is important for maintaining overall fitness and for weight management. Commonly, people with knee OA find an exercise bike to be a good option as it’s non weight-bearing (thus not as aggravating as walking) and encourages knee movement. Cycling has the added benefit of helping flush synovial fluid around the knee, which helps keep the joint surfaces lubricated and is good for the health of the articular cartilage. Swimming is also another cardiovascular exercise option people with knee OA commonly find beneficial.
Strength exercises: this includes exercises for the front of thigh (quadriceps), buttocks (gluteal muscles), calves and hamstrings. There should be a mixture of isolated muscle group exercises (eg, calf raises onto tip toes, or hip exercises with resistance bands) and combined or functional exercises (eg, variations of squats and bridges). As a person improves with their strengthening exercises, it is important they be progressed to provide an ongoing challenge and to stimulate further improvement.
Neuromuscular exercises: this category includes exercises that work on coordination, balance and stability. This is important to help a person with knee OA learn to position their leg well to avoid excessive stress on their knee joint. This type of training also translates well into movements and scenarios encountered in daily living. Examples include exercises on ‘fit balls’ to add a stability component or various leg movements while maintaining trunk and knee alignment.
Stretching: if a person has muscle tightness placing extra load on their knee, they may be shown flexibility exercises (eg, for the calf, hamstring or front of hip).
Additionally, several other strategies form part of a program of self-management for knee OA. These include: very low-calorie diets for weight-loss (under supervision of a dietician) followed by lifestyle modification; using heat or cold packs on the knee; using simple medication (as discussed with your GP) such as paracetamol; and pacing techniques that teach a person how to modify their daily activity to avoid large flare-ups of knee pain followed by periods of inactivity.
How long until I feel better?
Although research into OA and regenerative technology is advancing, there is currently no accepted way to reverse the cartilage changes of OA and, thus, it is a chronic condition. There are many options as discussed above to manage the symptoms of knee OA in order to minimise its impact on lifestyle, however OA is a condition that does need ongoing management.
The nature of the condition is one where symptoms fluctuate and do progress over time, though a long-term management plan incorporating strength exercise, weight management and activity modification, in conjunction with simple pain medications (as required, in discussion with your GP), is the best strategy for slowing the progression of OA, managing symptoms and optimising function. In some cases, though, a surgical opinion will eventually be required to discuss the need for total knee replacement.