You’re walking, standing, or maybe just stretching, and something behind your knee doesn’t feel quite right. “Why does the back of my knee hurt?” you may ask yourself. Pain behind the knee can be frustrating, especially when it’s hard to pinpoint what’s causing it. Whether it’s a dull ache, a sharp pull, or swelling that comes and goes, knee pain is a common issue with a range of possible causes.
At Orthopedic Specialty Institute, we help patients identify what’s really behind their symptoms and guide them toward effective treatment. Let’s take a closer look at what can cause pain behind the knee, how to know when it’s time to seek help, and what treatment options are available.
7 Common Causes of Pain Behind the Knee
Several different structures run through the back of the knee, including tendons, muscles, nerves, and blood vessels. If something becomes irritated, inflamed, or injured, it can lead to noticeable discomfort. Below are the most common reasons we see patients for pain behind the knee.
1. Hamstring Tendon Strain or Tear
The hamstrings are a group of muscles that run down the back of your thigh and attach near the back of your knee. Overuse, poor flexibility, or a sudden strain (especially during running or jumping) can lead to small tears in the hamstring tendons.
Hamstring Injury Symptoms
- A dull or sharp pain behind the knee
- Tightness in the back of the thigh
- Discomfort during activity, especially while bending the knee
Treating Hamstring Strains
- Rest and ice
- Physical therapy focused on stretching and strengthening
- Gradual return to activity to avoid reinjury
2. Baker’s Cyst
A Baker’s cyst (also called a popliteal cyst) is a fluid-filled sac that forms behind the knee when there’s excess joint fluid, often due to underlying arthritis or a meniscus tear. The cyst may feel like a lump behind the knee and can cause tightness or pressure when the leg is extended.
Symptoms of a Baker’s Cyst
- Swelling or a bulge behind the knee
- Aching or stiffness
- Limited knee range of motion
Treating a Baker’s Cyst
- Treat the underlying condition (arthritis, meniscus tear, etc.)
- Aspiration (draining the fluid) if the cyst is large or painful
- Cortisone injections to reduce inflammation
3. Meniscus Tear
The meniscus is the cartilage that cushions the knee joint. A tear in the posterior horn (the back portion of the meniscus) can lead to pain behind the knee, especially with twisting, squatting, or bending.
Symptoms of a Meniscus Tear
- Catching or locking of the knee
- Pain during knee flexion
- Swelling or stiffness
Treating a Meniscus Tear
- Physical therapy and anti-inflammatory meds for minor tears
- Arthroscopic surgery may be needed for larger or persistent tears
4. Calf Muscle Tightness or Strain
Tightness or strain in the gastrocnemius, one of the major calf muscles, can radiate pain to the back of the knee. This is common in runners, athletes, or anyone who overuses their lower leg muscles without enough stretching.
Symptoms of a Calf Muscle Injury
- Pain behind the knee when walking downhill or flexing the foot
- Calf tightness or cramping
- Mild swelling
Treating a Calf Muscle Strain
- Stretching and foam rolling
- Physical therapy exercises
- Rest and ice during acute flare-ups
5. Arthritis
Both osteoarthritis and inflammatory arthritis (like rheumatoid arthritis) can affect the back of the knee, especially if the joint lining is inflamed or bone spurs are present. Over time, cartilage breakdown can lead to pain, swelling, and stiffness.
Symptoms of Arthritis in the Knee
- Pain with prolonged standing or walking
- Morning stiffness that improves with movement
- Grinding or creaking sensations
Treating Knee Arthritis
- Physical therapy and lifestyle changes
- Anti-inflammatory medications
- Injections or surgery for advanced cases
6. Posterior Cruciate Ligament (PCL) Injury
The PCL is one of the major ligaments that stabilizes the knee. Injury often occurs during trauma, like falling on a bent knee or a car accident.
Symptoms of a PCL Injury
- Pain and swelling behind the knee
- Difficulty walking or bearing weight
- Instability or “giving out” feeling
Treating a PCL Injury
- Rest, bracing, and physical therapy for minor injuries
- Surgery may be needed in severe or complex cases
7. Deep Vein Thrombosis (DVT)
While less common, a blood clot in the deep veins of the leg can cause pain behind the knee. This is a medical emergency and requires immediate attention.
Symptoms of Deep Vein Thrombosis
- Sudden swelling in the calf or leg
- Warmth, redness, or discoloration
- Pain that worsens with standing or walking
When to Seek Emergency Help
If you experience these symptoms, seek medical attention right away.
When to See a Specialist for Pain Behind the Knee
If your pain is persistent, worsens over time, or is accompanied by swelling, locking, or instability, it’s time to see an orthopedic specialist. Diagnosing the root cause of pain behind the knee often requires a physical exam and imaging (like X-rays or MRI), especially if there’s concern for a meniscus tear, cyst, or ligament injury.
Personalized Treatment Starts Here
At Orthopedic Specialty Institute, we don’t just treat symptoms; we identify the root cause of your pain and build a personalized plan to help you recover fully. Whether you’re an athlete, weekend warrior, or just trying to stay mobile and active, we’re here to help you feel your best.
Request an appointment today to get expert care for knee pain that’s holding you back.
