Back of knee pain

Pain at the back of the knee can come from several sources: a fluid-filled sac (Baker’s cyst), tight or strained hamstring muscles, cartilage damage, or ligament strain. Sometimes pain is referred from arthritis or inflammation inside the joint.

The good news: most causes settle with rest, ice, stretching, and strengthening. Serious causes are less common and usually have obvious warning signs.

Pain behind the knee when walking often comes from a Baker’s cyst or hamstring strain being stretched as the knee straightens with each step.

You may feel it more when walking uphill (more knee bend) or after walking a distance. Rest, ice, and gentle stretching usually ease it. If pain persists beyond 2 weeks, see your GP.

Pain when bending the knee (squatting, crouching, climbing stairs) suggests hamstring tightness or a Baker’s cyst being compressed.

Gradual, gentle stretching and strengthening of the hamstrings help over weeks. Avoid deep bends while acute; as pain settles, gently increase range.

Pain when straightening the knee can come from a tight hamstring or Baker’s cyst. Stretching the hamstring helps reduce tension.

Sit with your leg extended and gently lean forward; hold 30 seconds. Repeat 2–3 times daily. Most people feel improvement within 1–2 weeks.

Back-of-knee pain after running often comes from tight hamstrings (overworked during running) or from a Baker’s cyst flaring from activity.

Cool down properly after running, then stretch your hamstrings when muscles are warm. If pain persists, ease running distance and frequency until pain settles.

Swelling behind the knee is often a Baker’s cyst or fluid from inflammation inside the joint. Swelling with pain is usually the joint responding to overuse or wear.

Rest, ice, compression, and elevation help swelling settle. If swelling is severe and sudden, or if it comes with heat and fever, contact your GP same-day.

A Baker’s cyst is a fluid-filled sac that forms behind the knee, usually because of wear or damage inside the joint. It may feel like a lump or cause a tight sensation.

Many Baker’s cysts cause no symptoms and need no treatment. If it is painful or limits movement, ice, compression, and rest help. If the underlying joint problem is treated, the cyst often settles.

Very rarely, a cyst can rupture, causing sudden swelling and pain in the calf—contact your GP if this happens.

The hamstring muscle runs from the buttock down the back of the thigh and attaches behind the knee. Tightness or strain in the hamstring causes pain along its length, including behind the knee.

Hamstring pain often comes from sitting too long, overuse (running or sports), or muscle weakness. Stretching and strengthening exercises help significantly. Most hamstring problems settle within 4–6 weeks with consistent stretching.

The calf muscle sits below the back of the knee and can cause referred pain upwards. A calf strain, cramp, or tightness can feel like back-of-knee pain.

Stretching your calf (stand facing a wall, step one leg back, lean forward with heel down) often eases this. If calf pain is sudden and severe, or if there is significant swelling, contact your GP—rarely, this can signal a blood clot.

The popliteus tendon (a small tendon that unlocks the knee) or hamstring tendon attachment can become inflamed, causing pain behind the knee.

Tendinitis usually comes from overuse and responds to rest, ice, stretching, and progressive strengthening. Pain typically settles within 4–8 weeks.

A meniscus tear can cause referred pain anywhere in the knee, including behind it. Meniscus damage may come with locking, catching, or instability.

Most meniscus tears improve with physiotherapy and time, though some need imaging to confirm the diagnosis.

A sprain of the posterior capsule (the tissue at the back of the knee) or a PCL (posterior cruciate ligament) injury can cause pain behind the knee, especially with swelling.

These usually come from a direct blow or twisting injury and need assessment to rule out serious damage.

Arthritis inside the knee joint can cause pain anywhere in the knee, including referred pain behind it. Osteoarthritis is most common, especially as people age.

Pain usually settles with gentle movement, stretching, and strengthening. Ice and heat can both help—find what your knee prefers.

Most back-of-knee pain is not serious. Seek same-day help if:

• Sudden severe pain with swelling (possible cyst rupture or acute injury)
• Calf is swollen, hot, or very painful—especially with shortness of breath
• The knee locked suddenly and will not straighten
• You cannot put weight on the leg after an injury

Rest, ice, and gentle stretching settle most back-of-knee pain within 2–4 weeks. If pain comes from a Baker’s cyst or hamstring tightness, consistent stretching is key.

For pain that persists, physiotherapy helps identify the exact cause and prescribe targeted treatment. Your GP can refer you.