Causes Of Pain In Back Of Knee When Straightening Leg

The knee is the largest joint in the body. It’s also one of the most complex because it connects two bones, the femur and tibia, with four ligaments and four muscles. While there are many different causes of pain in the back of your knee when straightening out your leg. Most can be treated through rest, ice and over-the-counter medications.

Causes Of Pain In Back Of Knee When Straightening Leg

Blood Clots

Blood clots can be caused by a variety of factors. For instance, they may be the result of a blood-thinning medication that you take. Such as Coumadin (warfarin sodium) or Lovenox (enoxaparin sodium). Blood thinners are often prescribed to patients who’ve had heart attacks and strokes in order to prevent further clotting. Sometimes, though, blood clots form even when taking these medications as directed: people have different responses to different drugs.

Blood clots can also form after an injury or surgery. Or in people with certain types of clotting disorders (like antiphospholipid antibody syndrome). If you’re at risk for developing deep vein thrombosis due either to your age or other underlying conditions (like pregnancy). Ask your doctor about what steps you can take to prevent this from happening.

Muscle Strain

Muscle strain is the most common cause of pain in the back of your knee when straightening your leg. Pain can be felt on either side of the knee joint and may also extend down into your calf muscle. The pain will typically be dull or achy. And you may have difficulty bending and straightening your leg due to stiffness.

Muscle strains occur when you overuse a particular muscle group by performing repetitive movements. Such as running or weightlifting, without adequate warm-up time. These muscles can become strained after even one strenuous workout session if not stretched before beginning activity.


It is also called degenerative arthritis, which refers to the condition where the cartilage is damaged and wears off gradually. This can cause pain and swelling in joints, making movement difficult.

Arthritis is most common in people over 65 years old. However, it can occur at any age if you have poor joint health or genetics that make you more likely to develop this condition. In addition, obesity and repetitive stress on joints are known causes of arthritis. If you have knee pain when straightening your leg, this could be caused by an injury or arthritis related to aging (osteoarthritis), but there are other possibilities as well.

Causes Of Pain In Back Of Knee When Straightening Leg


One of the most common causes of knee pain is tendinitis. Tendinitis is an inflammation of the tendons in your body. Which is why it’s also called tendon inflammation. Tendonitis can be caused by overuse, such as from running too much or playing contact sports. It can also be caused by a sudden injury. Like getting hit in the leg with a ball or falling down and landing on your knee.

Tendinitis is often confused with bursitis because both are types of joint pain that involve swelling and can occur at the same time. The difference between them lies in where each occurs: bursae are small sacs filled with synovial fluid that cushion our joints.

Tendons attach muscles to bones, so they’re able to move easily. They’re made up mostly of collagen fibers bundled together tightly, so they don’t stretch easily–which means that if one gets injured badly enough it might tear completely through its protective covering (called fascia).

If this happens then there won’t be enough tissue left inside those spaces between bones where things should go safely, instead there will just be open space so whatever’s left inside will fall out onto other parts nearby causing further damage until no one knows how bad their injuries were before surgery began.


A cyst is a small sac filled with liquid. It can form anywhere in your body, either as an abnormal growth or because of inflammation. Abnormal cysts that occur in the back of the knee are often caused by trauma to the area, such as falling or twisting your leg. They may also be associated with disease or injury elsewhere in your body, including arthritis and gout.

There are several different types of cysts, but they all have several things in common: they’re usually not painful; they don’t cause any symptoms except for their appearance; and they usually resolve on their own without treatment over time (although some will require surgical removal). To prevent cysts from forming on your backside when straightening out your leg while working out, remember these tips:

Lactic Acid Buildup

Lactic acid buildup is one of the most common causes of knee pain. It’s a byproduct of anaerobic respiration, which occurs when your body is unable to deliver oxygen to your muscles at the rate required for aerobic respiration (the normal process by which cells break down glucose and release energy). If you do not take in adequate amounts of oxygen, this can lead to lactic acid buildup in your muscles. As a result, they begin to cramp up and feel sore.

Lactic acid is produced when anaerobic respiration occurs—that’s why it hurts so badly after you’ve had a particularly strenuous workout or done some intense exercise like lifting weights or running long distances. However, even just walking around can cause enough muscle fatigue that it produces lactic acid within minutes if you’re not taking in enough oxygen during that activity.

Causes Of Pain In Back Of Knee When Straightening Leg

Knee Pain Has Many Causes

Causes of knee pain are various and depend on the person. One of the most common causes is overuse. If you’re overweight and walk for long periods of time every day, this can cause pain in your knees. It also happens when you do squats or lunges without proper form, which puts more pressure on the knee joint than it should be under.

Knee injuries can also happen from falling down stairs or off bicycles, especially if you don’t wear protective gear like helmets or pads to protect yourself from harm during these activities.

Knee pain may also be caused by tight muscles surrounding the joint that restrict movement within it; this is called patellofemoral syndrome (PFS). PFS often affects young adults who engage in sports such as basketball or volleyball.

As well as older people who suffer from arthritis-related conditions such as osteoarthritis (OA). Finally, one common cause of knee pain among all ages is arthritis; while OA usually affects only one side at a time—if both knees hurt at once, then there might be another issue going on!

Pain in the back of your knee can be caused by different things, including injuries and arthritis. The symptoms are often similar to those that indicate a knee injury, but there are important differences between the two conditions.