Swelling behind your knee, also known as a popliteal swelling, can be caused by various conditions, including a Baker’s cyst, arthritis, or a knee injury. If you notice a lump or fluid buildup in this area, it could indicate inflammation or an underlying medical issue.
Studies show that Baker’s cysts account for up to 20% of knee swelling cases and are often linked to osteoarthritis, which affects nearly 32.5 million adults in the U.S. Other possible causes include deep vein thrombosis (DVT), affecting about 1 in 1,000 people annually, or a torn meniscus, which is responsible for around 14% of knee pain cases.
Read this to find out the common causes, symptoms to look out for and treatments to get relief
Causes of Swelling Behind the Knee
Swelling behind the knee can result from a variety of causes, each contributing to the discomfort and mobility issues you may experience.
1. Baker’s Cyst (Popliteal Cyst)
One of the most common is a Baker’s cyst also known as a popliteal cyst. This fluid filled sac forms behind the knee due to excess synovial fluid often produced in response to knee joint damage or tissue inflammation.
Baker’s cysts commonly occur in people 35 to 70 years old especially those with a history of knee problems or who are into sports.
2. Injury
Injuries to the knee is a common cause of swelling and pain. These injuries can affect various structures within the knee joint and can be very uncomfortable and mobility limiting.
Among the most common types of knee injuries are ligament injuries and meniscus tears each with different symptoms and treatment approaches for knee injury.
3. Ligament Injuries
Ligament injuries like ACL and PCL are known to cause knee pain and swelling. Tears or sprains in these ligaments can cause fluid to accumulate in the knee and swelling and discomfort will be noticeable. These injuries usually occur from high impact activities or sudden movement that strains the knee joint.
The instability caused by ligament injuries can limit movement and make it hard to do everyday activities. The affected knee feels unstable and there’s always the fear of the knee giving way.
This instability plus the pain and swelling is why it’s important to seek medical attention for ligament injuries to prevent further damage and proper healing.
4. Meniscus Tears
Meniscus tears is another common cause of swelling and pain behind the knee. The meniscus is a C-shaped cartilage in the knee that acts as a shock absorber and stabilizer of the joint. When torn it can cause knee problems including swelling and severe pain. These tears occur during activities that involve twisting or turning the knee.
Symptoms of meniscus tear can vary but often includes feeling of knee locking or catching during movement.
This can severely limit knee function and make it hard to do daily tasks. The swelling and pain of meniscus tear emphasizes the need for proper diagnosis and treatment to get back to normal knee function.
5. Arthritis
Arthritis is a common condition that can cause knee pain and swelling. It’s the degeneration of joint cartilage resulting to inflammation and swelling within the knee joint.
This can severely limit mobility and quality of life so it’s important to know the type of arthritis that affects the knee.
6. Rheumatoid Arthritis
Rheumatoid arthritis is an autoimmune condition that causes chronic inflammation in the joints including the knee.
As you can see, this inflammation can cause swelling and pain behind the knee and affect daily activities and overall well-being.
7. Tendinitis
Tendinitis is another common cause of knee pain and swelling. It’s the inflammation of the tendons around the knee such as hamstring or gastrocnemius tendons. This inflammation can cause localized swelling and discomfort often made worse by physical activity.
8. Infections
Infections can also cause swelling and pain in the knee. Joint infections often caused by bacteria can cause severe pain and swelling and needs immediate medical attention.
Two common types of infections that affect the knee are septic arthritis and cellulitis.
9. Septic Arthritis
Septic arthritis is a serious infection in the knee joint that can cause swelling, redness and pain. This condition is often caused by bacteria that spread through the bloodstream or a direct injury to the knee joint. Common symptoms are severe pain, joint swelling and fever which can worsen rapidly if not treated immediately.
Moreover, the urgency of septic arthritis can’t be emphasized enough as it can cause rapid joint destruction and permanent damage if left untreated.
10. Cellulitis
Cellulitis is a bacterial skin infection that can cause swelling and redness in the tissues around the knee. This can develop fast and can lead to systemic infection if not treated immediately. Symptoms of cellulitis are redness, warmth and swelling in the affected area which can sometimes extend to the knee joint.
In addition to localized symptoms, cellulitis can also cause fever and chills which means the infection has spread.
11. Deep Vein Thrombosis (DVT)
Deep vein thrombosis (DVT) is a condition where a blood clot forms in the deep veins of the leg which can damage nearby blood vessels. This can cause swelling, pain and warmth in the affected area including behind the knee.
DVT is a serious condition that needs immediate medical attention to prevent life threatening complications such as pulmonary embolism.
12. Bursitis
Bursitis is the inflammation of the bursae which are small fluid filled sacs around the knee. This inflammation can cause swelling and discomfort often made worse by repetitive movements or prolonged pressure on the knee.
13. Gout
Gout is a form of arthritis caused by the accumulation of uric acid crystals in the joints. This can cause sudden and severe pain, swelling and redness in the affected area including the knee.
14. Popliteal Artery Aneurysm
Popliteal artery aneurysm is an abnormal dilation of the popliteal artery which can cause swelling and pulsating sensation behind the knee. This condition can cause blood clots and needs close monitoring and treatment to prevent further complications.
15. Referred Pain
Referred pain is when pain from one part of the body is felt in another area. Conditions in the hip or lower back can sometimes cause referred pain and swelling in the knee area.
Symptoms to Watch For
If you have knee swelling, it’s important to recognize the associated symptoms. Baker’s cysts for example forms a lump at the back of the knee and can cause stiffness and discomfort. Pain from Baker’s cyst can worsen during physical activities or when fully bending or straightening the knee.
Some symptoms to watch for:
- Stiffness and can’t fully bend the knee
- Pain and swelling after prolonged activity or standing
- A big cyst blocking the veins in the leg causing pain and swelling
Diagnosis
Doctors will gather information on previous knee injuries and symptom descriptions to form an initial diagnosis. X-rays will show narrowing of joint space and signs of arthritis, MRIs will show cysts, meniscus tears and other underlying conditions.
Ultrasound is very useful in diagnosing knee problems as it can determine if the lumps are solid or fluid filled and can detect problems with tendons and ligaments that can’t be seen through other imaging tests.
Also, joint aspiration, a procedure to collect fluid from the knee can detect signs of infection, bleeding or presence of crystals which can aid in accurate diagnosis.
Non Surgical Treatments
Non surgical treatments are often the first line of treatment for knee swelling and pain. These include lifestyle changes, use of anti-inflammatory drugs and physical therapy. Non surgical approaches can alleviate symptoms without the need for surgical procedures.
Rest and Ice
Rest and ice are the first two components of the RICE protocol which stands for rest, ice, compression and elevation. Applying ice packs to the knee can reduce swelling and numb the pain in the affected area.
Resting with ice can reduce swelling and recovery time. By giving the knee rest, you allow the body to heal and using ice to manage pain and swelling, it’s a simple and effective way to treat.
Physical Therapy
Physical therapy is important in building strength and flexibility in the knee to improve mobility and reduce swelling. By incorporating specific exercises and stretches in rehabilitation, physical therapy can manage knee swelling and overall function.
A physical therapist will create a customized exercise plan to improve strength and flexibility in the knee to aid in recovery and prevent future injuries.
Medications and Injections
Medications are used to reduce swelling behind the knee and improve mobility and comfort. Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen are prescribed to alleviate pain and reduce swelling.
Steroid injection can provide quick relief from inflammation and swelling by delivering anti-inflammatory medication directly into the joint space. These treatments can shorten recovery time and improve quality of life for those with knee swelling.
Surgical Options
If non surgical treatments don’t provide relief, surgical options may be considered. Arthroscopic procedures allow doctors to repair joint damage through small incisions and a camera, making the surgery less invasive. Partial knee replacement focuses on the most damaged part of the knee, a less invasive option to total knee replacement.
Total knee replacement involves replacing damaged bone and cartilage with an artificial joint, a total solution for severe cases. Osteotomy is another surgical option that can realign the knee joint and reduce arthritis pain.
Preventing Knee Injuries in 9 Ways
Incorporate both dynamic and static stretching in your routine to improve muscle readiness and flexibility and reduce knee injuries. Strengthen the key muscle groups like quadriceps, hamstrings and glutes through exercises like squats and lunges to support the knee joint.
Proper movement techniques and warming up before high impact activities is key to preventing knee injuries.
1. Balance and Stability Training
Do balance and stability exercises like yoga or Pilates to improve proprioception and coordination to prevent knee injuries. Strengthening core muscles also supports body mechanics and protects the knees.
2. Flexibility and Stretching
A stretching routine is important to maintain flexibility of the muscles around the knee. Dynamic stretching before activities and static stretching after can prevent tightness and reduce the risk of injury.
Target the hamstrings, quadriceps, calves and hip flexors to further improve flexibility and knee health.
3. Footwear
Choose supportive shoes with good arch support and cushioning to prevent knee injuries. Check and replace worn out shoes regularly to ensure they still provide support and shock absorption during physical activities.
4. Warm Up and Cool Down
Do a proper warm up before exercising to prepare the muscles and joints for activity to reduce the risk of injury. Follow up with a cool down that includes stretching to promote recovery and flexibility to maintain overall knee health.
5. Gradual Progression
Progress gradually to avoid overloading the knee and injuries. Listen to your body and be aware of any discomfort to adjust your activities accordingly to be safe and effective.
6. Cross Training
Incorporate low impact activities in your training to reduce stress on the knees and prevent repetitive strain. Cross train with exercises like swimming, cycling or elliptical training to add variety and maintain overall fitness without overloading the knee joint.
7. Healthy Weight
Maintain a healthy body weight to reduce stress on the knees during daily activities and exercises. A balanced diet supports health and weight management and knee health.
8. Proper Technique
Use proper technique during exercises and sports to minimize the risk of knee injuries. Get professional guidance from a coach or trainer to learn correct movement patterns and safe and effective workouts.
9. Regular Check Ups
Schedule regular check ups with a physical therapist or sports medicine specialist to assess knee health and address any issues early. If you experience persistent pain or discomfort seek professional advice to prevent further injury and proper treatment.
When to Get Help
See a doctor if knee pain is affecting your sleep or daily activities. If swelling persists for more than 3 days despite home treatment, seek medical help to address the underlying issue and prevent further complications.
Chronic Conditions
Managing chronic conditions like rheumatoid arthritis requires a combination of medications, lifestyle changes and regular check ups to reduce joint pain and swelling. Non-drug strategies like a balanced diet and consistent physical activity are important components in managing chronic joint pain due to rheumatoid arthritis.
Visit your healthcare provider regularly to adjust treatment plans based on your symptoms. Do low impact aerobic exercises like swimming and cycling to strengthen the knee and minimize impact.
Bottom Line: Key Takeaways
Non surgical treatments like rest, ice and physical therapy can manage knee swelling and may progress to surgical options if these don’t work.
Baker’s cysts due to excess synovial fluid are one of the main causes of swelling behind the knee especially if you have a history of knee problems.
Swelling can come from various injuries like ligament tears, meniscus tears and chronic conditions like arthritis so proper diagnosis and treatment is necessary.
