Blood clot behind the knee which in medical terms is called as popliteal vein thrombosis is quite a serious medical condition. It can cause potentially serious complications, if it is not treated on time. The most common complication of a blood clot behind the knee is pulmonary embolism. Anatomically speaking, the popliteal vein runs behind the knee and transports blood from the back of the knee to the heart. The symptoms of a blood clot behind the knee include pain and swelling along with erythema around the knee and the leg region. [2]
The blood clot occurs as a result of reduced blood flow to the popliteal vein or damage to the blood vessels in the area. It may also occur as a result of a trauma or injury to the back half of the knee. This normally happens during a tackle while playing contact sports like football or rugby. A study conducted on the prevalence of blood clot behind the knee reported that out of 3000 people who were diagnosed as having thrombosis in the lower extremities around 2% of people had blood clot behind the knee. This pointed to the rarity of the condition.[1]
The primary cause in these confirmed cases of blood clot behind the knee was believed to be long bus or airplane rides where the knee was in flexion for prolonged periods of time. Among all the participants, the first sign of a thrombosis was observed after a diagnosis of pulmonary embolism. To further study the pathogenesis of this condition, the popliteal veins were examined in varied functional states. This revealed folds when the knee was in flexion which were age-related and resulted in transient impairment of blood flow behind the knee.[1]
The study concluded that prolonged flexion of the knee along with impairment of venous backflow were the reasons for the development of blood clots behind the knee.[1]
What Causes Blood Clot Behind Knee?
The popliteal vein carries blood from the leg to the inferior vena cava in the heart. A blood clot behind the knee becomes life-threatening when the clots breaks free and lodges in the lungs causing pulmonary embolism. Reduced or impaired blood flow to the leg and knee is believed to be the primary cause of blood clot behind the knee.
Why does this happen is not entirely clear but long plane rides where the knee is in flexion for prolonged periods is one of the causes. In some cases, there is no obvious cause identified for the blood clot behind the knee.[2]
There are certain risk factors that increase the risk of an individual developing blood clot behind the knee. These risk factors include being on bed rest for long periods of time. This is normally seen in the elderly population where the individual is literally bedridden. People who abuse nicotine are also at increased risk for developing blood clots. Pregnancy also increases the risk of the female developing blood clots behind the knee due to the increase pressure being put on the knee with the weight of the fetus. People who are overweight or obese are also at increased risk for developing blood clots behind the knee.[2]
There are also certain medical conditions which can increase an individual’s risk for developing blood clot behind the knee. These conditions include certain forms of cancer. A fracture of the hip or knee also increases the risk of developing blood clots behind the knee. People who have had an injury to the spinal cord also tend to develop blood clot behind the knee. People with a family history or a previous medical history of blood clots also are at increased risk for developing blood clots behind the knee.[2]
There are also certain genetic conditions like thrombophilia or sickle cell anemia that can develop blood clots behind the knee. At times, surgical procedures done to the knee also result in the development of blood clots behind the knee. Some females who use birth control pills or have hormonal imbalance and are on hormone replacement therapy also tend to develop blood clots behind the knee. Age also plays a role in the development of blood clots in that it is normally seen in people above the age of 60.[2]
How is Blood Clot Behind Knee Treated?
Coming to the treatments of blood clots behind the knee, there are a variety of options which include
Anticoagulants: This is the most preferred treatment given for all forms of blood clots, including the one behind the knee. Anticoagulants are commonly referred to as blood thinners these medications work by preventing formation of blood clots and do not allow existing blood clots to progress. This in turn reduces the risk of the individual developing pulmonary embolism.[2]
The usual course of anticoagulants should be prescribed by specialists who are experienced in treating blood clots and should not be prescribed a general physician. Some examples of common anticoagulants used to treat blood clots behind the knee include warfarin and heparin. The initial course of anticoagulants is at maximum twice a day for a period of at least three weeks.[2]
In some cases, a patient may be asked to continue these medications for longer period of time if there is an increased risk for formation of blood clots in the future. Some people experience increased bleeding and easy bruising on anticoagulants and should speak with their physician if this occurs.[2]
Vena Cava Filter: This treatment is given for people who are not deemed to be a candidate for starting anticoagulant medications and are at increased risk for developing pulmonary embolism. This device is implanted into the inferior vena cava and any clot that travels from the lower extremities through this vein is stopped by this filter from progressing towards the lungs. This significantly decreases the risk of a pulmonary embolism.[2]
Thrombolytic Therapy: This form of treatment is reserved for people who have very large blood clots which cannot be treated by anticoagulant therapy alone. This therapy involves administration of medications that dissolve the blood clots. At times, it also involves surgically removing the clot. In majority of the cases, a thorough evaluation of the patient is done before he or she is deemed a candidate to undergo this form of treatment for blood clots.[2]
Compression Stockings: This is more of a preventive measure for blood clots rather than a treatment. These stockings are designed in such a way that they increase blood flow to the lower extremities including the knee. This in turn prevents blood clots from forming behind the knee. Compression stockings are only suggested for people with increased risk of clots or a previous history of this condition.[2]
These stockings are also helpful in preventing post-thrombotic syndrome which is yet another serious complication of blood clots. An individual with post-thrombotic syndrome will experience severe pain and swelling in the lower extremities along with a sensation of the legs feeling heavy. The individual will also have leg cramps on a frequent basis due to this complication.[2]
In conclusion, a blood clot behind the knee is medically referred to as popliteal vein thrombosis. It is a serious condition which puts the affected individual at risk for developing pulmonary embolism which is a life-threatening condition. The most common cause for a blood clot behind the knee is when the knee is in flexion for prolonged periods of time. This is usually seen in long airplane rides.[2]
At times, the popliteal vein can get damaged as a result of trauma. This usually happens during contact sports like rugby and football after being tackled from behind. The damage causes an interruption of blood flow resulting in blood clot behind the knee. An individual with blood clot behind the knee should be immediately evaluated and started on treatment to prevent complications like pulmonary embolism.[2]
There are a variety of treatment options for blood clot behind the knee in the form of anticoagulants, vena cava filters, and even at times surgery. The treating physician after assessing the condition can formulate the best treatment plan for the patient to manage blood clot behind the knee.[2]
