Back of Knee Pain: Causes, Seriousness, Relief

Most back of the knee pain, known as posterior knee pain, comes from an injury. Certain health conditions, such as arthritis, cysts, nerve damage, and blood clots, can also cause it. Some are serious and require treatment from a healthcare provider.

Although many knee injuries heal on their own over time, other types require surgery. It’s helpful to know what may be causing your knee pain so you can figure out the best way to manage it. 

Knee pain is a common type of pain that affects people of all ages. Knee injuries and overuse can cause problems with specific muscles, joints, tendons, and ligaments at the back of the knee. It’s possible to only feel pain in certain areas that aren’t anywhere on your knee.

Pain at the back of the knee will feel different based on the cause. Some of the most common ways people experience knee pain include:

• Soreness, either immediately after an injury or hours later
• Muscle cramps or spasms, which feel like sudden twinges of pain
• Soreness that may or may not get better when you aren’t using the muscle
• Dull or mild pain that slowly gets worse over time
• Feeling like your knee is unstable or can’t support your weight
• Tenderness when touched
• Swelling and/or warmth
• Severe pain during movement
• Tightness or stiffness 
• Inability to rotate, bend, or extend the knee fully without stiffness or pain
• Radiating pain that may be severe
• Numbness, tingling, or burning sensations

There are many reasons why you may experience pain on the back of your knee, such as overusing those muscles, leading to strains or swelling, or underlying health conditions like arthritis. Each cause has unique symptoms that can help make it easier to identify why you’re in pain.

Muscle Strain

There are several muscles behind your knee, and straining any one of them can cause posterior knee pain. These are the most common muscles related to pain behind the knee:

• Hamstring: Located on the back of your thigh between your pelvis and knee. 
• Gastrocnemius: This makes up most of your calf, the large muscle on the back of your leg under your knee.
• Popliteus muscle: A stabilizing muscle on the back of your knee that rotates with movement.

These muscles are often strained or pulled during intense physical activity or heavy lifting, especially if you don’t properly warm up or stretch before exercising. Anyone who overuses or overextends one of these muscles can end up with pain in the back of their knee. Muscle strains usually cause stiffness, swelling, and dull, aching pain that often feels better during rest and healing over time. 

Tendonitis

Tendons are tissues that attach a muscle to a bone. When a tendon becomes inflamed and swollen, it’s called tendinitis. Unlike muscle strains, which can happen when you overwork or misuse a muscle one time, tendons usually get inflamed with repeated stress or strain. Athletes are more likely to develop tendinitis because they use the same body parts all the time. 

Bursitis, which is similar to tendinitis, is inflammation of the bursa. A bursa is a small sac that cushions the space between muscles, tendons, and bones. Tendon pain can sometimes come from a swollen bursa beneath the tendon rather than the tendon itself. Both bursitis and tendinitis may cause sudden, intense pain, swelling, redness, and inability to move the joint. Both conditions usually heal on their own, but sometimes tendinitis needs physical therapy, surgery, or other treatments.

Ligament Injuries

Ligaments are similar to tendons, but they connect bone to bone and provide stability. There are several ligaments near the back of the knee that can be injured and result in posterior knee pain. The most common ligament is the posterior cruciate ligament (PCL), which connects the upper part of your leg to the lower part, and you can fully or partially tear your PCL.

A PCL injury is fairly serious and is sometimes part of a more complicated injury involving other ligaments or parts of your knee. Injuring your knee when it’s in a flexed or bent position is one of the most common ways to tear the PCL. 

After injury, your knee may swell and become stiff, and the pain may slowly get worse over time. You may feel like you can’t put pressure on it to walk. Ligament tears can heal on their own, but they may also require surgery.

Joint Problems

A joint is a part of your body where two bones meet and work together to allow for movement. There are a few potential joint problems that may cause pain in the back of your knee, such as:

• Baker’s cyst: This is a type of cyst (a small pocket or sac of fluid) that forms in the small pit at the back of your knee between your muscles and is non-cancerous. Common in people who have had previous knee injuries and people with arthritis. Baker’s cysts can cause tightness, swelling, and pain at the back of the knee, especially during physical activity. They usually go away with home care and minor treatments.
• Meniscus tear: Two pieces of cartilage in the middle of your knee joint, called menisci, cushion the bones as you move. Athletes can tear menisci during physical activity. People who are older may also tear their menisci as the cartilage wears down with age. Some people who tear their menisci feel a popping sensation when it happens. Over the next few days, people begin to have pain, swelling, and stiffness. A meniscus tear may heal on its own or require surgery.
• Arthritis: There are many different types of arthritis, but they are all caused by joint inflammation. Your knee is a common place to develop arthritis because of how often you use it and how much weight you put on it each day. People with arthritis usually feel joint pain, swelling, and stiffness. There’s no cure for arthritis, but it can be managed with lifestyle changes, regular exercise, physical therapy, over-the-counter (OTC), and prescription medications.   

Deep Vein Thrombosis (DVT) 

A specific type of blood clot called a deep vein thrombosis (DVT) is one of the only serious, potentially life-threatening causes of posterior knee pain. DVTs usually occur in leg veins, so it could be a cause of sudden, severe pain behind the knee. Symptoms of DVT include redness, swelling, pain or tenderness, and warmth, typically only in one leg. 

The biggest complication of DVT is a pulmonary embolism, which is when a blood clot in the leg travels to the lungs. A pulmonary embolism can be fatal, so it’s important to get medical attention right away if you think you have a DVT. You’re at a higher risk for DVT if you smoke, regularly sit for long hours (like on a plane), are pregnant, have obesity, are over 60 years old, take certain medications (like birth control pills), or have health conditions like cancer.

Compressed Nerve

Pressure on the sciatic nerve can cause pain in the back of the knee. The sciatic nerve starts in your lower spine, goes through your pelvis, then splits into two parts, each one running down the back of your legs to your toes. Pressure on the sciatic nerve near the spine can trigger pain anywhere along the nerve’s path to your feet, including the back of your knee. 

Problems with your vertebrae, the disc-like bones of your spine, or injury to the spine or pelvis can cause sciatic nerve pain. It might feel like sharp cramping, electric shocks, or a milder, radiating pain. You may also have weakness, numbness, tingling, or burning at the back of your knee when your sciatic nerve is inflamed. Sciatic nerve pain usually goes away on its own after several weeks, but a few people may need surgery.

You may not need to see a healthcare provider for your posterior knee pain, but some causes of knee pain won’t heal on their own and can’t be treated at home. See a healthcare provider if:

• The pain is severe even when you are resting
• Doesn’t get any better after three days of home remedies 
• The knee looks swollen or misshapen
• The knee slides, shifts, locks, or buckles when you put weight on it
• The knee feels warm
• You’re experiencing burning, tingling, or numbness behind your knee
• You can’t fully bend or stretch out your leg at the knee joint
• You hear a clicking sound in your knee when you move
• Your leg below your knee feels cold or looks blue
• You heard a tearing or popping sound at the time of your injury

One cause of knee pain is potentially life-threatening: DVT. It’s important to get immediate medical attention if you have any symptoms of DVT, including sudden swelling, pain, redness, warmth, tenderness, and cramping.

Healthcare providers have many different ways of diagnosing knee pain depending on the cause. Your provider may use one method or a combination of methods to figure out what’s causing your pain. 

• Physical exam: Your provider will look at the back of your knee, checking for signs of swelling, bruising, redness, or misshapen muscles or ligaments. They’ll also gently feel around the part of your knee that hurts to see if putting pressure makes your pain worse. This also lets them feel for areas of warmth or swelling, fluid-filled pockets, or anything out of place.
• Range of motion tests: Not being able to rotate, bend, or extend your knee is a common symptom of many posterior knee injuries, so your provider may want to see how well you can move your knee. They will also listen for clicking sounds and feel for any abnormal sliding or shifting when the knee is moved. 
• Imaging tests: These tests can help your provider see exactly where the problem is stemming from. You may need an X-ray, magnetic resonance imaging test (MRI), or computed tomography (CT) scan. None of these tests is painful or requires any special preparation.
• Synovial fluid analysis: In some cases, your provider may use a needle to draw a small sample of the fluid in your knee joint to see if you have arthritis or an infection. They will usually numb the area first, which can be mildly painful. The test only takes a few minutes.

You can start with a primary care physician if you need to see a healthcare provider for knee pain. If more in-depth testing or treatment is necessary, a primary provider might suggest you make an appointment with an orthopedic specialist, a doctor specializing in diagnosing and treating conditions involving the bones, joints, ligaments, tendons, and muscles.

Treatment for your knee pain depends on the cause. Some causes heal on their own with basic home care, while others need surgery or more intense treatments.

• Home remedies: Minor injuries, like tendonitis or a muscle strain, typically heal on their own over time. You can relieve pain and speed up the healing process by practicing the RICE protocol: rest, ice, compression, and elevation. 
• Medication: You may need to take medication to relieve pain and decrease swelling while you heal or wait for other treatments to work. OTC medicines, such as nonsteroidal anti-inflammatory drugs (NSAIDs), can help with your symptoms. NSAIDs include aspirin (acetylsalicylic acid) and Advil (ibuprofen). Your provider may recommend injecting a steroid medication into your knee to help with the pain and swelling. In some cases, prescription pain relievers may be necessary. If arthritis is causing your knee pain, topical creams and gels with pain-relieving ingredients may help.
• Physical therapy: If you’re recovering from an injury or surgery to repair an injury, your provider might recommend physical therapy. A physical therapist can guide you through a safe treatment plan to strengthen your knee muscles and increase your flexibility or range of motion. 
• Surgery: Severe injuries may need surgery. This is more likely with torn ligaments or joint cartilage, though sometimes cysts and conditions like knee arthritis may need surgery. If your knee pain is from a compressed nerve in your spine, surgery may be necessary if the pain is severe. 

Pain in the back of your knee usually stems from an injury or inflammation of the muscles, tendons, ligaments, or joints. Sometimes, chronic (long-term) pain conditions like arthritis or a compressed nerve in your spine can cause knee pain. Deep vein thrombosis (DVT) is a life-threatening blood clot that can cause posterior knee pain.

Treatment involves a combination of home remedies and OTC or prescription medications until the injury heals. In more severe cases, surgery is necessary. If you have arthritis, you can’t cure your knee pain, but you can work with your healthcare provider to create a treatment plan to help manage it.