Arthrosis of the knee: an overview of Gonarthrosis

By Cristiano Antonino On May 23, 2023

Gonarthrosis is a particular form of arthrosis affecting the knee. Widespread mainly among the elderly, and among those who are overweight, it is one of the most common forms of arthrosis

Conservative and surgical treatments are offered to patients, but there is no definitive cure for this condition.

Osteoarthrosis, in all its forms, is in fact a degenerative disease: over time, the cartilage (a kind of cushion that covers the bones and makes them elastic, reducing friction between them in the joint) thins out, and the bones are more susceptible to inflammation.

The treatment of gonarthrosis is therefore aimed at treating its symptoms, typically represented by knee pain, with reddening of the skin and swelling, joint stiffness and ‘joint peeling’.

Gonarthrosis: what it is

Gonarthrosis is osteoarthritis of the knee.

It is one of the most frequent causes of knee pain and swelling.

It occurs when the cartilages on the upper surface of the tibia and lower surface of the femur wear down and become thinner, exposing the bones to increased friction: as the joint moves, they therefore rub against each other and this is responsible for an inflammation that tends to become chronic.

The knee is in fact a synovial joint located between the femur, patella and tibia

The lower surface of the femur is lined and protected by articular cartilage, which plays a primary role in preventing friction damage; the joint is then lined from the inside by the synovial membrane, which produces synovial fluid.

This not only reduces friction between the components of the joint, but also has a lubricating action that facilitates the functioning of tendons and ligaments.

An anti-friction and lubricating function is also performed by the synovial bursae (small membrane sacs filled with fluid), while the stability of the knee is ensured by the internal and external meniscus, which – located on the upper part of the tibia – are made of cartilage.

The painful symptoms caused by gonarthrosis occur when an inflammatory process is triggered in the knee.

The balance between cartilage synthesis and degradation veers towards degradation, and the cartilage slowly wears out.

The pain, however, is not generated by the cartilage, which lacks receptors, but by the receptors located at the level of the subchondral bone (below the joint): this is why, when the pain arrives, arthrosis is already in an advanced stage.

Gonarthrosis, the causes

Generally, gonarthrosis is bilateral (i.e. it affects both knees).

The inflammation is due to the degeneration and progressive thinning of the cartilage: the femur in its lower part and the tibia in its upper part touch and damage each other, becoming inflamed.

A combination of causes triggers gonarthrosis:

age: the main risk factor for knee arthrosis is ageing, as cartilage degenerates mainly in older people (the peak occurs between the ages of 70 and 79);
being overweight or obese: extra kilos stress the knees and it becomes very common to experience pain. In addition to overloading the knee, fat cells synthesise inflammatory substances that facilitate the onset of arthrosis;
gender: women over the age of 55 are more likely to suffer from knee arthrosis;
genetic predisposition: there are numerous genetic disorders that predispose to osteoarthritis;
history of knee injuries: especially if the injuries have been numerous (as is often the case for those who play rugby, football, basketball, American football, tennis, dirt running and combat sports), it is more likely that gonarthrosis will develop in adulthood. The most ‘indicted’ injuries are cruciate ligament injuries and meniscus tears, because they alter the stability of the joint;
the removal of parts of the meniscus: such surgery also involves the removal of part of the cartilage;
rheumatoid arthritis, which is responsible for anatomical changes in the affected bones;
metabolic diseases such as Paget’s disease, a chronic skeletal disorder characterised by accelerated bone turnover in certain areas.

Gonarthrosis: symptoms

The typical symptom of gonarthrosis is pain.

The knee consists of three areas: the inner area (medial femoral-tibial compartment), the outer area (lateral femoral-tibial compartment) and the area between the femur and the patella (patellofemoral compartment).

In 88% of cases, arthrosis affects the medial femoral-tibial compartment, while the other two compartments are affected in 67% and 16% of cases, respectively.

The pain experienced is a mechanical pain, i.e. it worsens with movement and physical activity.

And it is usually accompanied by other symptoms

swelling
redness and a feeling of warmth
joint stiffness, especially on awakening or after a period of immobility
emission of creaking or cracking noises when moving the joint

Gonarthrosis, the types

There is no single type of gonarthrosis.

On the contrary, one speaks of

medial (or internal) patellofemoral gonarthrosis
lateral femoro-tibial gonarthrosis
patellofemoral gonarthrosis

Depending on which type you suffer from, you will experience a typical pain.

Medial patellofemoral gonarthrosis is the most common form of knee arthrosis.

Its main symptom is pain, which starts from the inside but radiates to the entire joint, and its typical manifestation is the varus knee (the femur and tibia together form an obtuse, medially open angle).

Lateral patellofemoral gonarthrosis is rarer, and presents as a valgus knee (or ‘X-knees’): the pain is felt in the anterolateral area but, when the inflammation is in an acute phase, can extend to the entire knee.

Patellofemoral gonarthrosis is characterised by the absence of pain: in most cases it is asymptomatic, and is only diagnosed following an X-ray.

Gonarthrosis: Diagnosis

When you experience severe knee pain, associated with joint stiffness that impairs daily activities, you should contact your general practitioner.

He or she will refer you to an orthopaedist specialising in knee pathologies, who will formulate a diagnosis and determine the most appropriate therapy.

The specialist will analyse the patient’s symptoms and family history before prescribing a diagnostic test: X-ray or MRI.

Specifically, the X-ray is used to check for the presence of osteophytes (osteophytes are excrescences at joint level, small bone spurs similar to a claw that characterise bones affected by osteoarthritis).

Nuclear magnetic resonance, which is more comprehensive than X-rays, allows the level of degeneration and thinning of cartilage to be assessed, as well as the state of the ligaments and menisci and the presence of any joint effusion.

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Therapy

To date, there is no definitive cure for gonarthrosis.

There are only therapies aimed at controlling or resolving its symptoms, so that the person no longer feels pain and regains normal knee function.

The goal is to reduce pain when bending and stretching the leg, and to restore at least partial joint mobility.

Conservative therapy includes:

diet and physical activity aimed at weight loss, in overweight or obese patients;
targeted exercise to strengthen the lower limbs without overloading the knees;
taking pain-relieving drugs and NSAIDs;
physiotherapy to strengthen the thigh muscles and increase knee mobility;
injections of corticosteroids or hyaluronic acid into the knee, but only if the NSAIDs have had no effect;
prescription of a brace, on the advice of the orthopaedist and depending on the state of the joint.

Should conservative therapy fail to produce results, surgery remains the only option.

There are three options:

arthroscopy, to clean the cartilage of the knee (minimally invasive, has reduced efficacy and tends to be reserved for younger patients)
osteotomy of the femur or tibia: this consists of remodelling the deteriorated joint bone and is generally prescribed for patients with damage to the cartilage of only one of the two bony parts involved in the joint;
installation of a prosthesis to replace the real knee (being an invasive operation, with an effect lasting up to twenty years, it is recommended for patients over 55)

Therapy, whether conservative or surgical, gives appreciable results in terms of improvement or resolution of symptoms. However, curing gonarthrosis is not possible.

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