Pain behind the knee (posterior pain) when straightening leg

What Should I Do When I Feel Pain Behind My Knee When I Straighten It?

Pain in the back of the knee, often called posterior knee pain, can result from a variety of reasons. The structures of the knee, consisting of muscles, tendons, ligaments, cartilage and vascular system, can each be affected, resulting in a variety of injuries.

Some conditions may only require rest, pain medication, knee elevation above the heart and a warm compress to get better. However, others may need surgical interventions and may become worse over time if left untreated.

It is always best to seek a doctor if the pain does not resolve with rest and pain medication, if the swelling worsens, if there are considerable changes in the appearance of the knee, or if daily activities involving the knee become difficult.

Is A Feeling Of Numbness Behind The Knee Serious?

Numbness in the knee usually signals a problem in the nervous system. A tingling sensation, pain and swelling commonly accompany the numbness. The femoral nerve carries the signals that allow one to feel sensations at the back of the knee. It allows us to feel touch, vibration, pain and temperature.

Damage to the femoral nerve and any of its branches can result in numbness in the knee. A direct injury at the back of the knee, a knee replacement surgery, diabetes, or tight clothing that compresses the nerve can all cause damage to the femoral nerve.

Numbness at the back of the knee can be a potentially serious condition depending on the cause of the numbness and the extent of the damage in the femoral nerve. If not properly diagnosed and treated, numbness and impaired sensation may become permanent.

Is Pain Behind The Knee A Blood Clot?

One of the causes of posterior knee pain is DVT. If you have incurred a fracture, severe muscle injury, or have gone through major surgery, the vein at the back of your leg may be injured. A direct injury to the vein can result in DVT, where a clot forms at the back of the leg. DVT can also be caused by prolonged bed rest, immobilizing the leg through casting or bracing, leg paralysis, or blood disorders.

If you feel deep, throbbing pain at the back of the leg, accompanied by swelling, redness, and warmth in the surrounding skin, you must call your doctor immediately as DVT is a condition that can cause serious complications.

I Am Training For A Marathon And Have Started To Feel Pain Behind My Knee Whenever I Run. Do I Need To Rest It Or Do I Need Treatment?

If you experience pain behind the knee while running, it is better to rest and observe other symptoms that may develop. Because there are many reasons for knee pain, it is always best to seek the advice of a doctor or a physical therapist.

Resting the affected leg, taking pain medication, and refraining from high-impact activities can be enough to manage most conditions affecting the knee. However, if the pain and swelling do not resolve on the following day or worsen, or if you develop other symptoms such as redness and warmth in the affected area, you need to consult your doctor to obtain a proper diagnosis. Always remember that the earlier the injury gets treated, the better the healing and the faster you can return to your usual activities.  

Reasons Why Your Knee Hurts When Straight

If the back of your knee hurts when you straighten it, several conditions may be responsible. A physician can easily diagnose some, while others require special diagnostic equipment to fully understand the condition.

Some of the causes of posterior knee pain are:

  • Posterior Cruciate Ligament (PCL) Injury
    • The PCL and the ACL (Anterior Cruciate Ligament) are the ligaments that form the “X” structure found inside the knee joint. The PCL is responsible for preventing the shin bone from moving backward excessively relative to the thigh bone. It is the strongest ligament of the knee and provides stability and support during walking and running.
    • The most common cause of a PCL injury is a force applied to the front of the knee. A PCL injury often results from landing on the knee when falling or an automobile accident leading to a “dashboard injury” where the knee impacts the vehicle’s dashboard.
    • The symptoms of a PCL injury include immediate pain and swelling, stiffness, knee instability, and difficulty in walking.
  • Hamstring Injury (Biceps Femoris Tendonitis)
    • The group of muscles located at the back of the knee is collectively called the hamstrings. These muscles help in bending or flexing the knee. The hamstring is composed of three muscles: the biceps femoris, semitendinosus, and semimembranosus.
    • When the tendon of the biceps femoris gets strained or stretched, it can cause a sudden pain on the outside of the back of the knee. It can also result in swelling, bruising, weakness in the back of the leg, and difficulty straightening the knee.
    • A hamstring injury is common among athletes such as runners and basketball players who sprint frequently. Failure to do warm-up exercises, tight thigh muscles and weak buttocks muscles (called the gluteus) are some of the factors that predispose an individual to a hamstring injury.
  • Gastrocnemius Tendonitis
    • The gastrocnemius muscle is the muscle located at the back of the lower leg. It originates from the base of the thigh bone, crosses the knee joint, and attaches to the heel bone. The gastrocnemius allows you to bend your knee and point your foot and toes downward. This ability makes the gastrocnemius crucial for running and walking.
    • The gastrocnemius tendons may become strained or stretched when the knee is straight and the toes are pointing upwards. Gastrocnemius tendonitis – an inflammation of the gastrocnemius tendon – usually occurs in cyclists, especially if their bike seat is too far back or too high. The common symptoms of this condition are pain and stiffness in the calf muscle extending at the back of the knee. This pain easily goes away with rest, the elevation of the leg and icing of the affected area. If you experience gastrocnemius tendonitis, you should lower the intensity and frequency of the activity to avoid further damage to the tendon.
  • Baker’s Cyst
    • A Baker’s cyst, also called a popliteal cyst, is characterized by the formation of a sac filled with fluid in the space at the back of the knee called the popliteal fossa.
    • This fluid, known as synovial fluid, lubricates the knee joint to prevent the bones and other structures from rubbing each other during movement. If excessive pressure is placed on the joint, such as after an injury or because of arthritis, the fluid can leak outside the joint and into the back of the knee, creating the cyst.
    • Other than the sac, a Baker’s cyst may not have other symptoms. Sometimes, if the swelling is extensive, it can cause knee pain, stiffness and difficulty straightening and bending the knee.
  • Arthritis
    • Arthritis is an umbrella term for conditions characterized by the degeneration of the cartilage which cushions and protects the joint.
    • Osteoarthritis is the most usual type of arthritis and occurs due to the normal wear and tear of the knee joint as we age. This type of arthritis is common among the elderly.
    • Rheumatoid arthritis is an autoimmune disease where the immune system erroneously attacks the cartilage of the knee joint. This type of arthritis occurs in both knees at the same time.
    • Gout is a type of arthritis caused by the accumulation of uric acid in the joints, which results in inflammation. Although this is common in the big toe, it can also occur in other joints such as the knees. It causes extreme pain that often wakes the affected individual up at night.
  • Deep Vein Thrombosis (DVT)
    • When the blood passes slowly through the deep vein at the back of the leg, a clump of blood cells (known as a clot) could form, resulting in DVT. DVT is a potentially life-threatening condition as the clot can become dislodged and enter the bloodstream. When the clot reaches the lungs, it can cause blockage resulting in a condition called pulmonary embolism.
    • The symptoms of DVT include throbbing or cramping pain, swelling, redness, warmth and tenderness in the affected area.

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