Pain Behind the Knee: 5 Possible Causes and When to Act

Pain behind the knee often feels different from other knee pain: more like tightness, fullness or a pulling sensation in the hollow of the knee, especially when you bend the leg fully or straighten it after sitting. Most causes are harmless and respond well to simple care, but there is one sign you should never ignore.

Here are the five most common causes and how to tell them apart.

1. A Baker's cyst

When the knee produces extra joint fluid, for example with osteoarthritis or a meniscus problem, some of it can collect in a small pouch at the back of the knee. You feel it as a soft swelling and a sense of fullness that gets worse when you bend the knee fully or stand for a long time. The cyst itself is usually harmless, and it often settles once the cause inside the knee calms down.

2. Strained tendons at the back of the thigh

The muscles at the back of the thigh attach just below the knee, on both sides. After a sprint, a sudden lunge or a lot of uphill walking, their tendons can become strained. The pain sits at the sides of the hollow of the knee and is strongest when you bend the knee against resistance, for example when pulling your heel towards your buttock.

3. A pulled calf muscle

The calf muscle starts just above the back of the knee. A sudden push-off, like a quick start or a jump, can strain it. Typical: a sharp pain at the top of the calf, sometimes with a feeling as if someone kicked you, then pain when you walk on your toes.

4. The back part of the meniscus

Damage to the rear part of the meniscus often shows up as a deep pain at the back of the knee when you squat, kneel or bend the knee fully. Swelling and a catching feeling can come with it.

5. Osteoarthritis

With wear of the joint, the whole knee can feel stiff and "full", including the back. The pain is usually worse after rest and in the morning, and it eases once you get moving.

The sign you must not ignore

A blood clot in the leg can also cause pain behind the knee or in the calf. See a doctor the same day if the calf is swollen, warm, red or painful to the touch, especially after a long journey, surgery or a period of bed rest. Do not massage the leg and do not put on a sleeve until a doctor has ruled out a clot.

What you can do at home

• Avoid deep bending for a while. Squats, kneeling and sitting on your folded legs put the most pressure on the back of the knee.
• Keep the knee moving gently. While sitting, slowly bend and straighten it 10 times, a few times a day.
• Cold for swelling. 10 to 15 minutes of a wrapped cold pack after activity.
• Gently stretch the calf and the back of the thigh, without pain, once the acute phase is over.
• Raise the leg in the evening if the back of the knee feels full and swollen.
• Gentle, even support. Once a clot has been ruled out, a soft sleeve that does not dig in behind the knee can give a feeling of stability during the day.

If the pain is more on the side of the knee, read our guides on pain on the inner side and pain on the outer side of the knee.

When to see a doctor

• the calf is swollen, warm or red
• the swelling behind the knee is growing or very painful
• the knee locks or gives way
• you cannot put weight on the leg
• the pain does not ease after 14 days of rest and home care

Most pain behind the knee comes from overload or extra fluid in the joint. With a little patience and the right care, it usually calms down.

A sleeve you will actually wear

The best sleeve is the one that does not end up in a drawer. The KeenTrove Bamboo Knee Sleeve is made for exactly that:

• soft, breathable bamboo, comfortable even in summer
• fits snugly but does not dig in behind the knee
• does not lock the knee, so you move naturally
• wear it under your clothes during the day and in bed at night

With 60 days to get your money back, you have nothing to lose.

See the bamboo knee sleeve →

Note: this article is for information only and does not replace an examination by a doctor. If you have circulation problems or diabetes, or have recently had knee surgery, talk to your doctor before wearing compression.