Pain behind the knee, also known as posterior knee pain, is a common concern with various potential sources. This discomfort can range from a mild ache to severe pain, often influenced by activity levels. Understanding the different causes, which involve muscles, tendons, nerves, blood vessels, and the knee joint itself, helps in finding appropriate relief.
Muscle and Tendon Related Pain
Muscles and tendons in the back of the leg are common sources of pain behind the knee. Activities like running, jumping, or sudden movements can strain these soft tissues.
Hamstring muscles, if strained or inflamed (tendinopathy), can cause pain behind the knee. This often results from overstretching or forceful movements, leading to sudden pain, swelling, bruising, and difficulty bending the knee. Calf muscle strains, especially the gastrocnemius, can also cause sudden pain and swelling in the lower leg that may extend behind the knee.
The popliteus, a small muscle behind the knee involved in rotation and stability, can also cause pain. Its tendon can become inflamed (popliteus tendinopathy) from overuse or repetitive activities like downhill running. Symptoms include pain on the outer side of the back of the knee, worsening with movement, especially when walking downhill or descending stairs.
Nerve and Vascular Related Pain
Pain behind the knee can also stem from conditions affecting nerves or blood vessels, some requiring prompt medical attention.
Sciatica, caused by irritation or compression of the sciatic nerve, can cause radiating pain down the back of the leg. This nerve-related pain presents as shooting, burning sensations, tingling, or numbness.
A deep vein thrombosis (DVT) is a serious condition involving a blood clot in a deep vein, commonly in the calf or thigh. Symptoms include swelling, warmth, redness, and pain behind the knee or in the calf, often affecting only one leg. A DVT requires immediate medical evaluation due to the risk of the clot traveling to the lungs.
Less common but significant vascular causes include popliteal artery aneurysm and popliteal artery entrapment syndrome. A popliteal artery aneurysm is a bulge in the artery behind the knee, causing throbbing pain, swelling, or a pulsing feeling. Popliteal artery entrapment syndrome occurs when calf muscles compress the popliteal artery, restricting blood flow to the lower leg. This leads to pain, cramping, numbness, or coldness in the calf during exercise that subsides with rest.
Joint and Cartilage Conditions
Structural issues within the knee joint can also cause pain behind the knee. These conditions often involve the cartilage or ligaments that provide stability and cushioning.
Meniscus tears involve the C-shaped cartilage pads that cushion the knee joint, often from twisting injuries or degeneration. Tears can cause pain, swelling, clicking, catching, or a locking sensation, often localized behind the knee, especially during squatting or bending. Injuries to the posterior cruciate ligament (PCL), which stabilizes the knee, can occur from direct impact to the shin, causing pain, swelling, and instability.
Osteoarthritis of the knee involves gradual wear and tear of joint cartilage, leading to pain, stiffness, and reduced range of motion. This pain can manifest behind the knee, particularly with movement or after inactivity. A Baker’s cyst (popliteal cyst) is a fluid-filled sac behind the knee, often resulting from underlying knee problems like arthritis or a meniscus tear. It can cause tightness, swelling, and pain behind the knee, worsening with activity. In some cases, a Baker’s cyst can rupture, leading to sudden, sharp pain and swelling in the calf.
Seeking Medical Attention and Initial Care
It is important to recognize when to consult a healthcare professional for pain behind the knee. Seek immediate medical attention if you experience:
Sudden severe pain
Significant swelling
An inability to bear weight
Numbness or tingling
Fever
Symptoms suggestive of a deep vein thrombosis (warmth, redness, or tenderness in the calf)
Persistent pain, pain that worsens, or pain that interferes with daily activities also warrants medical advice.
For minor strains or sprains, initial self-care steps can help manage symptoms. The RICE protocol—Rest, Ice, Compression, and Elevation—is a common first aid approach. Resting the affected leg and avoiding activities that worsen pain prevents further injury.
Applying ice packs for 10-20 minutes several times daily reduces pain and swelling. Compression with an elastic bandage minimizes swelling, and elevating the leg above the heart aids in reducing fluid buildup. These measures offer temporary relief and are not a substitute for a professional diagnosis if pain persists or severe symptoms develop.