7 Causes Of Knee Pain When Straightening The Leg & How To Relieve Them

Do You Get Knee Pain When Straightening Your Leg?

Watch the video to learn what causes knee pain straightening the leg, plus some easy tips you can use to be able to walk more comfortably without knee pain.

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!

What Causes Knee Pain When Straightening The Leg?

There are a number of different things that can cause knee pain when straightening your leg.

7 causes of knee pain when straightening the leg

  1. Stiff hamstrings
  2. Meniscus tear / Baker's cyst
  3. Tibiofemoral joint dysfunction
  4. IT band syndrome
  5. Patellar tendonitis
  6. Patellofemoral joint pain
  7. Fat pad impingement

I'll break these down by location as share what you can do to relieve your knee pain.

Pain In The Back Of The Knee When Straightening The Leg

One of the most common areas where people experience knee pain when straightening their leg is in the back of the knee.

Stiff Hamstrings

If your knee hurts in the back of the leg, particularly after sitting for a long period of time, it's often due to stiffness in the hamstring muscles.

When you sit for a long time with your knee bent, the hamstring muscles can tighten up, making it difficult to straighten your leg. You may feel stiff as you take your first few steps after standing up from sitting.

To alleviate this pain, one simple thing you can do is stretch your hamstrings.

To do this, sit on two chairs with one leg up on a chair and the other on the floor.

seated hamstring stretch

You can also do this with one leg on a bed or couch and the other on the floor.

Keep your knee straight and lean forward from the waist.

You should feel a stretch in the back of your leg behind the knee.

There are three hamstring muscles, two of which are attached to the inside of the knee and one that attaches to the outer side.

hamstring pain when straightening leg

The inner hamstring muscles tend to get stiffer when you sit with your knees together, so to stretch them, turn your leg so that your toes point outward as you lean forward.

inner hamstring stretch

What Else Can Cause Back Of Knee Pain When Straightening The Leg?

Sometimes a more serious injury like a meniscus tear or a Baker's cyst can cause swelling that pools in the back of your knee.   That swelling may also give you pain and stiffness when straightening your knee.

Pain On The Inside Of The Knee When Straightening The Leg

If you're experiencing pain on the inside of your knee when straightening your leg, it could also be due to a hamstring problem.

Specifically, the semitendinosus muscle, which is one of the inner hamstring muscles.

pain on inside of knee when straigthening the leg can come from the semitendinosis

The semitendinosis runs along the inside of the knee and attaches just below the knee joint.

To stretch this muscle, use the same inner hamstring stretch as described above.

You may have to play with it until you feel it in the right place.

Tibiofemoral Joint Dysfunction

Inner knee pain when straightening the leg can be caused by a joint dysfunction that develops between your thigh bone (femur) and your lower leg bone (tibia).

This dysfunction can be caused by sitting with your knee twisted inwards or by over-pronating when walking or running.

To alleviate this pain, cross one leg over the other.

Put one hand on the outer side of the tibia and put your other hand on the inner side of the femur, both close to where the knee bends.

Pull the tibia toward you and twist this way with your lower hand and push outward with your upper hand.

Pain On The Outside Of The Knee When Straightening The Leg

If you have pain on the outside of your knee when straightening your leg, it could be due to a joint dysfunction as mentioned above.

Additionally, pain on the outside of the knee could be caused by IT band syndrome.

IT Band Pain

Your IT band runs from your hip down to just below your knee.

When you walk or run, the IT band moves in front of the knee as you straighten your leg and behind the knee as you bend your leg.

Your IT band crosses over the knee joint when your knee is about 30 degrees away from being all the way straight.

As your IT band goes back and forth over the widest part of the knee (the lateral femoral condyle), it can get inflamed or irritated.  This is known as IT band syndrome.

Runners who over-train or have poor running technique have an increased risk of developing IT band pain.

Pain In Front Of The Knee When Straightening The Leg

Pain on the front of your knee when you're straightening your knee in the front of your leg can be from a few different things.

Patellar Tendonitis

Patellar tendonitis can cause pain on the front of the knees below the kneecap.

In this case, you get a  problem with the force production from your quadriceps muscle. Examples of this include knee pain doing squats, knee extension exercises, or lunges.

You may also get patellar tendon pain when landing from a jump.  That's why patellar tendonitis is also sometimes called "jumper's knee".

Patellofemoral Pain

Pain behind the kneecap is referred to as patellofemoral pain.

Patellofemoral pain is pain between the kneecap (patella) and thigh bone (femur).

Pain behind the kneecap can be caused by quadricep muscles that are too stiff.

I've done another video on how to stretch your quad muscles so I'll refer you to that video if you're having pain behind your kneecap from stiff quadricep muscles.

Pain Inside The Knee Joint

Finally what about if you have pain inside the joint when you're straightening your leg?

If  you have pain that's deep inside the joint, that often comes from a problem inside the knee joint itself.

Most of the time when you get meniscus tears, they are in the the back part of the meniscus.  Meniscus tears usually hurt worse when bending your knee.

However, sometimes you can get tears in the front part of the meniscus as well. Those types of tears may hurt more when straightening your leg.

What Does It Mean If You Can't Fully Straighten The Knee Without Pain?

There's also a little fat pad that sits in the front of your knee joint.

The infrapatellar fat pad can sometimes that can get impinged or pinched in the front part of the knee joint.

infrapatellar fat pad can get pinched in the front of the knee when straightening the leg

A fat pad impingement can keep you from straightening your knee all the way.

So if you're having trouble straightening your knee all the way without pain in the front of the knee, you may be pinching the fat pad.

Additionally, if you have bone spurs from knee arthritis, this can also prevent you from straightening your knee all the way.  This may or may not be painful.

Conclusion

So in conclusion, the 7 causes of knee pain when straightening the leg are:

  1. Stiff hamstrings
  2. Meniscus tear / Baker's cyst
  3. Tibiofemoral joint dysfunction
  4. IT band syndrome
  5. Patellar tendonitis
  6. Patellofemoral joint pain
  7. Fat pad impingement

If you need help for knee pain when straightening your leg, we'd be happy to help you. Just tap the button below to request an appointment with on of our knee pain specialists.

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