Why Is My Knee In Pain When Bending It?

Do You Get Pain When Bending Your Knee?

I commonly get asked the question: "Why is my knee in pain when bending it?"

In this video, you'll learn what can cause pain in the back, front, inside, and outside of the knee when bending it.   Plus, learn what you can do to be able to bend your leg more comfortably without knee pain.

What Causes Pain In The Knee With Bending?

There are many things that can cause your knee to hurt when bending it.  If you want to know what's causing your knee pain, it helps to start with location of the pain.

Common areas include:

  1. Pain When Bending Leg Behind Knee
  2. Pain When Bending Knee On Outside
  3. Pain When Bending Knee On Inside
  4. Front Of Knee Pain When Bending
Knee Pain Guide by Knee Pain Specialist Dr. Dave Candy. More 4 Life, St. Louis, Manchester, Ballwin, Chesterfield, Des Peres, Ellisville, MO Learn to relieve: knee pain when going up and down stairs, knee pain when sitting, knee pain when walking, and more!

Pain When Bending Leg Behind Knee

Pain behind the knee when bending your leg can be caused by several things:

  1. A hamstring or calf muscle problem
  2. A meniscus tear
  3. A sciatic nerve entrapment,
  4. A Baker's cyst.

To distinguish between these different causes, we first need to define two terms:

Active knee bending

Using your muscles to bend the knee.  Your hamstrings are the primary knee flexor muscles. However, your calf muscles (called the gastrocnemius) also cross the knee and assist in knee bending.

Passive knee bending

When the knee is bent by some other force other than your hamstring and calf muscles

Pain Behind Knee When Bending Actively

If you get pain in your knee when bending it actively but not passively, this usually indicates a muscle problem.  When you use your hamstring and/or calf muscles to bend your knee, they can become a source of pain.

Muscle pain can occur when muscles are:

  1. Overstretched - strained or mildly torn
  2. Understretched -  too stiff or too short

When you have a sore muscle, you might think that you should stretch it.  You're not alone.  Many people believe that you should stretch stiff muscles.

In reality though, this is only sometimes true. 

If your pain is caused by a strained (overstretched) hamstring muscle, then stretching it is bad idea.

However, if the pain is caused by a muscle that is too stiff or has trigger points, hamstring stretches or calf stretches may be a good idea.

Additionally, manual trigger point therapy or dry needling can be helpful.

Again though, before starting any type of treatment, you need to determine the root cause of the pain.

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Pain Behind Knee When Bending It Passively

If you get pain in the back of your knee when bending it passively, this can be cause by a meniscus tear or a Baker's cyst. Mot of the time though, the problem is not serious.

Click here to learn more about pain behind the knee.

Pain When Bending Knee On Outside

Pain on the outside knee of your knee when bending it is often caused by an IT band problem.

The Iliotibial Band (or IT Band) is a long, thick piece of fascia (kind of like a tendon).  It attaches muscles on the outside of the hip to the outside of the knee.

As you bend and straighten your knee when walking or running, the IT band moves back and forth over the outside of the knee. If the IT band is stretched too tightly over the outside of the knee it can become a source of pain.

If you read the previous section, you'd naturally think, "Well, if the IT band is too stiff, I should stretch it right?"

Not exactly.

The IT band is made of a stiff connective tissue called collagen that requires approximately 30,000-125,000 pounds per square inch to stretch.

That's probably not realistically going to happen with any amount of stretching, massage, or foam rolling.

However, you can stretch the muscles that attach to the IT band, particularly the gluteus maximus and tensor fascia late.  Stay tuned for a post to come on how to do that.

Learn more tips to help pain on the outside of the knee

Pain When Bending Knee On Inside

Pain when bending your knee on the inside of the knee is most often caused by a tendinopathy at the pes anserine. The pes anserine is the attachment point of 3 muscles on the inside of your knee: the sartorius, gracilis, and semitendinosis.

pain on inside of knee when bending

The latter of these three muscles, the semitendinosis muscle, is a hamstring muscle, which you use to bend your knee.  Many people tend to overuse their inner hamstring muscles and underuse their outer hamstring muscles.  This can cause pain on the inside of the knee when bending it.

Furthermore, if you overpronate your foot (let your arch flatten when walking) this causes your knee to twist inwards which can irritate the pes anserine tendons.  This in turn can cause pain on the inside of the knee when you walk.

Click here to learn tips to relieve pain on the inside of the knee.

Front Of Knee Pain When Bending

If the front of your knee is in pain when bending it, there's likely a problem with the flexibility of the muscles on the front of your thigh (quadriceps muscles).

As you can see from the picture below, your kneecap sits inside of your patellar tendon. Your patellar tendon attaches the quadriceps muscles to your shin bone.

Why is the front of my knee in pain when bending it?

When you bend your knee the quadriceps muscles get stretched over the knee. If they aren't flexible enough, it causes compression between the back of the kneecap (patella) and the front of the thigh bone (femur).  This in turn causes pain on the front of the knee called patellofemoral pain.

Pain On Front Of Knee With Passive Bending

When you passively bend your knee all the way back such as when kneeling or doing certain yoga poses such as child's pose, this stretches the quadriceps muscles to their endrange. This can cause pain on the front of the knee as the kneecap gets compressed against the thigh bone.

If this is the case, then simply doing some quadriceps stretches like the one in the video above, child's pose, or hip flexor stretches can help.

However, there is a reason why the muscles became stiff in the first place.  For passive bending, it may very well be that you just don't get in positions often that require you to fully bend your knee.

However, overusing your quadriceps muscles during everyday activities can also cause them to become stiff.

Pain on Front Of Knee With Eccentric Bending

If you get front of knee pain during activities such as squatting or going up and down stairs,  this type of pain can come from either a patellofemoral problem as noted above, or from patellar tendonitis.

When you squat or go down stairs, gravity is actually doing the work of bending your knee.  However, if you don't want your knee to bend super fast (9.8 meters/second/second - the acceleration of gravity), you have to use your quadriceps to slow down the motion. This is called using a muscle eccentrically, meaning the muscle is contracting (trying to shorten) while it's lengthening.

This type of muscle contraction puts a lot of stress on the quadriceps muscle and patellar tendon, which can create patellar tendinitis or tendinopathy.  This type of problem is a common causes of knee pain in jumping athletes, who have to control the bending of their knee while landing from a jump.

However, it can occur in non-athletes as well, particularly people who squat, lunge, or climb stairs a lot.

Keeping your weight more on your heels than your toes when squatting or going up stairs helps you use more of your gluteal muscles and less of your quadriceps muscles.

Learn more about pain on the front of the knee

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Knee Pain Guide by Knee Pain Specialist Dr. Dave Candy. More 4 Life, St. Louis, Manchester, Ballwin, Chesterfield, Des Peres, Ellisville, MO Learn to relieve: knee pain when going up and down stairs, knee pain when sitting, knee pain when walking, and more!

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