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Pain Behind Knee When Straight: 7 Possible Causes


Do you experience pain behind your knee when you straighten it out? If so, you’re not alone. This is a common problem that can be caused by many different things.

In this blog post, we will discuss the most common causes of pain behind the knee and what you can do to alleviate it. We will also provide tips for preventing this problem from occurring in the future.

The Knee Joint

Before discussing posterior knee pain, it is crucial to understand the anatomy of the knee joint. The knee joint is formed by three bones: the femur (thigh bone), tibia (shin bone), and patella. The bones are connected via soft tissues like ligaments and cartilage which hold them together and allow for movement.

There are four main ligaments of the knee, which include the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL).

The meniscus is a cartilage located between the femur and tibia, that acts as the joint’s shock absorber and assists to stabilize the joint. The meniscus is broken into two sections: medial and lateral meniscus.

Inside the capsule of the knee joint, there is also synovial fluid that lubricates and nourishes the joint.

Around the joint, there are also a number of prominent muscles that surround the popliteal fossa or back of the knee.

In the upper leg, these include the hamstring muscles and their associated hamstring tendons, which are broken into three separate muscles called the biceps femoris, semitendinosus, and semimembranosus.

In the lower leg, the associated muscles are calf muscles. There are two main calf muscles, the gastrocnemius, and soleus.

On the back of your knee, you also have the popliteus which is a small muscle that assists in the stabilization of the knee joint.


Common Causes of Pain Behind the Knee

Now that we understand the anatomy of the knee, let’s discuss the most common conditions of posterior knee pain.

  • Hamstring Injury: Hamstring injuries are usually the result of overstretching or repetitive strain. Symptoms include pain, swelling, difficulty bending your knee, and potential pain when straightening your knee. There are a number of specific hamstring injuries like a tear, strain, or tendinitis that can cause pain behind the knee.
  • Bursitis: When the bursa (fluid-filled sac) located at the back of the knee become inflamed and swollen, this can lead to pain behind the knee. There are a number of particular bursas that can cause knee pain in this area including a popliteal cyst (baker’s cyst) or semimembranosus bursa.
  • Ligament injury: Ligament injuries are knee injuries that can be caused by a sudden or repetitive strain culminating in an acute injury. Common ligament injuries causing pain behind the knee include a tear or strain of the ACL, PCL, MCL, or LCL. Symptoms include pain, swelling, instability, and possibly difficulty straightening your knee.
  • Meniscus tears: The meniscus is a fibrocartilage that lines the knee joint and helps to absorb shock. A meniscal tear is a knee injury that can cause pain when straightening your knee. These injuries are usually caused by trauma or repetitive strain on the knee joint like from squatting, running, or jumping.
  • Patellofemoral pain syndrome: This is a knee problem, also called runner’s knee, where the cartilage behind the kneecap becomes inflamed. This can result in pain and difficulty when bending or straightening your knee.
  • Arthritis: Arthritis is an inflammation of the joints which can cause pain and stiffness in the knees. Osteoarthritis, rheumatoid arthritis, psoriatic arthritis, and gout are some of the most common types of arthritis that can affect the posterior knee joint. Arthritis can be caused by repetitive motions over the duration of one’s life or be an autoimmune inflammatory disease.
  • Deep vein thrombosis: Deep vein thrombosis (DVT) is a medical condition that can cause pain behind the knee. DVTs are medical conditions caused by a blood clot in one of the deep veins near the back of your knee which can block circulation and cause swelling, warmth, or pain in the area.

In conclusion, there are many potential causes for pain behind the knee. It is important to seek medical attention if you are experiencing any pain or discomfort in this area to accurately diagnose and treat the underlying cause.

Diagnosing Posterior Knee Pain When the Leg is Straight

If you are experiencing pain when you straighten your knee, the best way to accurately diagnose and treat the condition is to talk to a qualified medical professional.

Your doctor will likely perform a physical examination of your knee as well as ask questions related to your symptoms like: How long have you had this pain? What type of activities makes your pain worse? Do you have any other symptoms like swelling, warmth, or redness?

Your doctor may also order imaging tests such as an X-ray or MRI to get a better look at the structures of your knee. Depending on their findings, they will recommend the best treatment for your particular situation.


Treatment Options for Posterior Knee Pain

The best course of treatment for posterior knee pain depends on the underlying cause and the severity of the injury. Generally, this may include one or multiple of the following:

• Resting the knee joint

• Ice therapy via ice packs or ice baths

• Taking over-the-counter pain relievers

Physical therapy exercises to strengthen your muscles

• Stretching exercises that can be provided by your physical therapist to improve the flexibility of your knee joint

• Wearing a brace or other supportive device for stability and support

• Surgery for severe cases

It is important to always follow your doctor’s recommendations and to never try to diagnose or treat yourself. The best way to manage posterior knee pain when you straighten your leg is by seeking medical attention from a qualified professional.

With the proper treatment and care, you can improve the condition of your knee joint and return to your everyday activities as quickly and efficiently as possible.