The swollen knee (also called “water in the knee”) is a common problem caused by fluid accumulation in or around the knee joint.
The knee swelling can occur suddenly or gradually and can restrict the movement of the leg, making walking very difficult.
Knee effusion develops mainly:
- after injury or distortion,
- due to arthritis (inflammation of the joints),
sometimes for no apparent reason.
What causes knee swelling?
The knee has a joint capsule that lies around the entire joint like a sac.
The capsule contains synovial fluid, which nourishes and lubricates the joint so that it can move without difficulty.
The joint capsule works like a container that holds the fluid inside the joint.
Knee swelling occurs when excessive fluid accumulates inside the capsule.
This can be caused by:
- Joint bleeding (haemarthrosis): usually caused by an accident and the knee swells quickly. The swelling can be very intense and cause stiffness throughout the leg.
- Accumulation of synovial fluid (water in the knee): in this case, the knee is prone to gradual swelling. In some cases, the swelling can go and come, and the amount of fluid in the knee is variable. Usually, the cause is osteoarthritis or arthritis.
- Knee swelling can be the result of surgical intervention, for example by replacing the joint with a prosthesis.
In this case, the swelling passes a few months after the operation. Before that, the pain passes.
My patients often ask me how much time it takes for the swelling to pass from the joint because they are in a hurry to heal.
I emphasize that healing and swelling are not so closely correlated.
The patient can return to work, as the knee can be painless after surgery despite swelling.
Sudden knee swelling
Usually, sudden knee swelling is caused after an injury caused by hemarthrosis. This is an accumulation of blood inside the joint.
In this case, a structure inside the knee is damaged, begins to bleed, thereby increasing the pressure on the joint. The swelling spreads and the knee resembles a balloon:
In this case, the joint effusion can be seen in the upper and lower area and on the sides of the knee.
The joint appears:
- sometimes bluish discolored.
There are 3 main causes of hemarthrosis:
1) Ligament rupture: one ligament tears off completely. This is a common cause and usually affects the anterior cruciate ligament of the knee (ACL).
In the case of a cruciate ligament injury, the knee cannot be bent further than 90/100° and it is not possible to stretch it completely for a few weeks.
2) Meniscus lesion: the hematoma occurs when the lesion is located in the outer area.
3) Knee fracture: the fracture of one of the bones that make up the knee joint. Knee swelling due to this type of injury requires urgent medical attention to avoid complications.Knee swelling after an accident
If knee swelling does not develop until some time after an accident (hour-days), it is very likely due to an increase in synovial fluid in the joint (or synovitis).
This happens if something inside the joint has been injured.
The swelling varies from case to case.
If you put one hand over both knees, you can feel that the knee is swollen and hot. This is a normal inflammatory reaction.
You can observe a bump at the front of the knee after a trauma. Then it is a bursitis of the knee.
The most common causes of knee swelling are: 1) Injury to the meniscus:
a lesion of the inner cartilage layer of the joint (the inner part of the meniscus is not supplied with blood and therefore does not bleed in case of injury).
2) Distortion of the knee: an overstretching or tear of the ligaments.
The accumulation of fluid in the knee can vary from day to day. Improvement usually occurs when the injury heals.
For soft tissue injuries (muscles and joint capsule), healing usually takes 6-12 weeks. Cartilage injuries may require surgical intervention because there is no blood supply.
Gradually swelling knee without injury
Possible causes of a knee swelling gradually and without trauma include chronic diseases such as:
- Arthrosis (occurs mainly in the elderly).
The swelling may vary depending on the day and the activities performed.
Usually, the swelling is not very pronounced.
Arthrosis (or joint degeneration) is the pathology that most often leads to swelling of this type.
Osteoarthritis causes the body to produce more fluid in the knee.
On days when the leg is overloaded, the knee can become inflamed, causing it to produce more fluid to try to protect and heal itself.
Swelling on the sides of the joints can be the result of a reduction in cartilage in these parts of the knee, as is usually the case in the early stages of osteoarthritis.
Knee swelling is less common on the outside than on the inside, which is a larger.
probability of developing osteoarthritis.
Swelling on the outside occurs mainly in a valgus position of the knee, because there is a greater load on the knee side.
Tendinitis is an inflammation of the tendon, especially the quadriceps tendon in the upper part (above the kneecap) and the patellar tendon in the lower part, but there is no swelling visible from the outside.
Knee that swells rapidly without injury
Sometimes swelling develops very quickly even without trauma. The most common causes of this phenomenon are:
1) Infection: Infections increase the production of synovial fluid. As a rule, infections develop after surgery or a deep incision and can penetrate to the joints.
Treatment of a joint infection is very difficult. Sometimes surgical intervention is also required to solve the problem.
2) Gout: high levels of uric acid cause the formation of crystals that settle in the joints.
The accumulation of these crystals causes inflammation in the knee, as well as a slight swelling.
Gout is treated by medication and by an adapted diet.
Laterally swollen knee
The swelling can also manifest itself outside the joint capsule (extra-articular swelling).
Typically, this is caused by:
- inflammation of one of the bursae of the knee (bursitis),
- trauma to the muscles surrounding the knee (hematoma).
The most common extra-articular swellings are:
1) Bursitis: Bursae are small fluid-filled sacs between bone and soft tissue and serve to reduce friction between tissue structures.
If friction increases in a certain disease, the bags may become inflamed.
In this case, the swelling is not extended over the entire knee joint, but is limited to the area of the bursa.
Swelling in front of the kneecap may be caused by prepatellar bursitis (maid’s knee).
A swelling localized in the back of the knee joint, more or less the size of an orange, can result from popliteal bursitis, also called Baker’s cyst.
2) Hematoma: a blunt trauma in the soft tissue of the knee joint can cause a bruise.
The blood that collects around the muscles can accumulate into hardening.
If there is only a slight bleeding, there is usually a small bruise, which is also called contusion.
Knee swelling after surgery
It is normal for a knee to swell after surgery. Often the patient also develops fever.
Routine surgery such as meniscus surgery after meniscus tear (meniscectomy) causes swelling that can last for a few weeks.
There is no need to worry about postoperative swelling, as the knee needs a lot of time to decongest.
After a VKB reconstruction (anterior cruciate ligament plastic), the knee needs about 4-6 months to decongest.
It is often observed that a joint appears much larger after surgery due to a fracture. This is a normal consequence. This is not an effusion, as the knee is hard in the swollen area.
Other causes of knee swelling
In most cases, the fluid that forms remains inside the knee joint, as the joint capsule acts as a barrier and prevents fluid from escaping. However, sometimes there is also an extra-articular swelling.
Infections can cause knee swelling, especially:
- Brucellosis, etc.
In this case, the doctor prescribes antibiotics to reduce symptoms.
Rare causes of knee swelling
1) Patellar luxation: during flexion extension, the kneecap slides in a groove at the front of the knee. An external force can act on her laterally and cause her to slip out of her anatomical seat. This trauma causes knee swelling.
2) Runner’s knee: inflammation of the patellar tendon can cause swelling at the front of the knee.
3) Bone tumor: there are different types of tumors that cause knee swelling even in children.
4) DVT: deep vein thrombosis is a blood clot that forms in one of the deep veins, usually on the leg.
Usually, these blood clots are painful and develop after long periods of being bedridden, after surgery or on long flights.
5) Hemarthros due to circulatory problems: is a sudden bleeding that occurs within the joints in patients with:
- with coagulation disorders,
- taking blood thinner medications such as Coumadin.
Swollen knee during pregnancy
Often, the knees swell during pregnancy, especially from the second trimester.
This phenomenon arises because the weight of the child increases, thereby provoking an increase in pressure of the uterus on the vena cava (a large venous blood vessel that carries blood from the legs to the heart).
This situation can lead to fluid retention at the knees, but can also affect hands and feet.
To reduce swelling on the legs, standing must be avoided for long periods of time. As often as possible you should take rest periods and put your legs up.
Standing for a long time increases pressure on the vena cava and reduces blood circulation.
Heat increases swelling on the legs, while cold gauze bandages reduce knee swelling.
During pregnancy, great care must be taken of swollen legs, as this could also be a sign of a serious illness known as preeclampsia or gestosis.
The doctor should be consulted to rule out a serious condition if the swelling:
- does not pass after sufficient periods of rest,
- involves different parts of the body.
The doctor must be told if the knee swelling occurs along with:
- Visual impairment
- Abdominal pain.
Knee swelling in children
Often children have swollen knees due to a bump or fall, but sometimes this could be related to other causes.
Knee swelling due to a strain is less common than in adults.
Lyme disease can cause inflammation and persistent swelling of the joints. Lyme disease is most common in the northeastern region of the United States. In these areas of greater risk, it is important to exclude this disease.
Children may have fluid retention in the knee due to:
- juvenile arthritis.
Septic arthritis is a painful infection accompanied by overheating and swelling. The bacterium that causes this infection usually affects the knee, but may also be present in other joints.
Therapy for knee swelling
There are many decongestant methods for the knee, but the choice of therapy depends on the cause of the swelling:
1) Ice: can be very useful to slow down blood flow and thus reduce swelling and pain. Important is the correct application of ice packs at intervals of 10 minutes.
2) Compression: to reduce swelling, apply an elastic bandage or knee brace to create proper compression for the knee.
3) Medications: Anti-inflammatory non-steroidal drugs (NSAPs) such as ibuprofen or voltaren may be prescribed to reduce knee swelling.
4) Aspiration: the fluid present inside can be drained by the doctor with a syringe. Sometimes the aspirated fluid can form again.
5) Cortisone infiltrations: Cortisone is a steroid hormone that reduces inflammation and pain by suppressing the immune system.
Natural remedies for knee swelling
If swelling and pain persist for more than 48 hours or occur together with fever and severe pain, a doctor must always be consulted to arrive at a correct diagnosis.
Loads on the painful knee should be avoided as long as the swelling persists.
An elastic bandage does not help to eliminate the swelling. Better is an envelope with green clay throughout the night.
Ice cream. Crush ice cubes, wrap in a cloth and place on your knee for 20 minutes. Ice relieves swelling and pain on the knee.
Repeat the envelope every 2-4 hours, raising the leg.
Ice only helps:
- in the first 24 hours after an injury,
- after onset/aggravation of pain.
High storage. You can put your foot up on a few cushions.
One trick to raise the leg is to raise the foot of the bed. So the ankles are higher than the heart during the night.
Exercises for rehabilitation. If you suffer from knee osteoarthritis, it is important to perform exercises:
- for stretching,
- to build muscle.
These exercises help to warm and stretch the muscles and are very effective after a long period of rest.
Regular physical exercise exercises serve:
- the improvement of muscle tone.
Do not overdo with the exercises if you are inexperienced.
Choose a moderate gymnastics that does not cause pain, such as:
- or swimming.
Overweight. If you are overweight, you have to adjust your diet to lose the excess pounds. To do this, you should always put yourself in the hands of a qualified nutrition expert.
Excess weight puts increased pressure on joints and muscles, especially the knees and ankles.
Too much pressure causes joint inflammation and is a risk factor for knee swelling.
Massage therapy is a helpful treatment that, along with the other methods, helps to reduce swelling in the knee.
Manual therapy promotes:
- the release of endorphins and other analgesic chemical substances,
- blood circulation.