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Why Stiff Knees Happen - Injury Overview

by Jaydee Vykoukal, PT, DPT February 28, 2018 0 Comments

close up knee

A stiff knee and knee pain should be taken seriously because of the effects it can have on your quality of life. Knee stiffness can even cause us to miss family gatherings and important events if severe enough. Stiff knees can plague people of any age, but it is more common among older people. Keep reading to better understand how stiff, achy knees can develop and to learn the best ways to treat your knee stiffness.

Understanding Knee Stiffness

Understanding knee anatomy will give us a clue as to what might be causing stiffness. Our knees are stabilized by two pairs of ligaments: the medial and lateral collateral ligaments and the posterior and anterior cruciate ligaments. Plus, there are also two pieces of cartilage, called menisci, which act as a cushion to protect the bones with movement. Additionally, there are other stabilizing connective tissues like the joint capsule itself, the kneecap, and other various large stabilizing muscles that cross the knee joint. Any of these parts of the knee may be damaged or imbalanced, causing a stiff knee and restricted movement.

Stiff Knee: No Pain

Sometimes, stiffness in the knee does not come with pain, although there could be some swelling that limits range of motion. If you are an athlete or runner, you may not notice the pain at first. However, if stiffness is ignored it will most likely worsen over time because of its effects on other local tissues that have to adapt.

What Causes Stiff Knees?

There are several causes of knee pain and stiffness, but they are generally organized into three categories:

Stiff Knee After Injury

The knee changes the way it moves if one of its structures is damaged. The most common injuries that can lead to knee stiffness include:

    • Meniscus Injury

      When damage to this cartilage limits joint mobility, the knee feels stiff. Sometimes, knee locking happens when a piece of damaged cartilage gets stuck inside the joint. A meniscus tear is most often caused by a sudden twisting motion or high impact to the knee itself.

      Meniscus Tear

    • Ligament Injury

      Swelling can be due to the pressure of blood vessel damage that leaks into the joints, causing knee pain and stiffness known as hemarthrosis. Bleeding into the joint cavity can occur when the ligaments, such as the PCL or ACL, are damaged. Additionally, extra blood flow is common with a knee injury as well to promote tissue healing and provide joint protection as well.

    • Fracture

      A bone fracture, usually caused by a high impact from a fall or sport, initiates a healing sequence in the body that brings extra blood flow. This means that bone healing cells are put to work to start the repair process. Thus, swelling, stiffness, and pain are expected as the healing occurs and keeps the sufferer motivated to rest and allow the body to do its job.

    • Sprain or Strain

      A knee sprain (of a ligament or the joint capsule) or muscle strain often leads to knee stiffness. Overstretching a ligament or muscles leads to swelling in the joint, affecting how the knee moves.

      More About Sprained Knees

    Stiff Knee After Prolonged Positions

    • Stiff Knees After Sitting

      Knee stiffness after sitting is often a secondary issue when you’re already dealing with an underlying injury, especially an acute injury or arthritis. Experiencing knee stiffness each time you get up from sitting can be frustrating and start to reduce your overall flexibility even with other activities.

    Stiff Knees in the Morning

    Like any position you spend a lot of time in, it can lead to stiffness. Our body’s like to move so that blood is flowing and tissues are supple. Sleep is definitely a time when knee stiffness can be exacerbated. Whether you sleep with your knee bent or straight, it can feel hard to move in the opposite direction in the morning until you get moving and warm your joints up.

    Stiff Knees from Running

    Many runners suffer from stiff knees before, during, or after their workouts. This can be due to overuse, muscle imbalances, or an underlying injury. Determining what part of your run is making your knees stiff can help you reduce this common issue.

    Stiff Knee Joints Due to Medical Conditions

    A number of medical conditions can cause inflammation that result in stiff knee joints. The most common are:

    • Gout

      This inflammatory arthritis develops due to a buildup of uric acid secondary to diet. Symptoms of gout include redness, pain, and warmth, and the knee feeling tight and stiff. Other forms of inflammatory arthritis that can cause stiffness include rheumatoid arthritis.

    • Bursitis

      There are bursae throughout the body that provide cushioning and help with smooth lubricating movements of local tendons. In the knee, there are four primary bursae in the front of the knee (anterior) and one in the back (posterior) under the hamstring tendons. Swelling in one of these bursas results in stiffness of the knee, particularly of the kneecap.

      Knee Bursitis

    • Osteoarthritis

      Also known as wear-and-tear arthritis, knee osteoarthritis happens when the cartilage between the knee joints breaks down. Without that cushion, the space between the bones decreases and the joint loses its smooth surfaces. Severe arthritis can warrant the need for a knee replacement surgery.

      More on Arthritis in the Knee

    Rare Causes

    There are a few rare causes of a stiff knee that are potentially life-threatening and require immediate medical attention. However, it’s important to keep in mind that these are very rare and highly unlikely.

    • Infection

      Infections, such as septic arthritis or osteomyelitis (inflection of the bone), are  rare causes of stiff knee joints. Infectious arthritis is a painful condition and should be treated by a doctor immediately.

    • Tumor

      An abnormal growth in the bone or other local tissues may cause the knee joint to swell, resulting in stiffness in the knee.

    Symptoms of Stiffness in Knee

    You use your legs every day, so you’ll know when your knees aren’t moving or feeling right. The following are other symptoms commonly associated with knee stiffness.

    • Redness
    • Knee joint pain when bending or straightening
    • Knee swelling/inflammation
    • Stiff knees in the morning
    • Knee instability
    • Stiff knees with prolonged sitting or standing
    • Muscle weakness
    • Burning pain or aching in other joints
    • Cracking or popping in the joints with movement
    • Locking of the joint with specific positions

    Thankfully, most of these symptoms can subside with time and appropriate treatment. However, ff you experience any of the following symptoms, talk to your doctor immediately for medical advice:

    • Fever
    • Loss of sensation in the lower leg
    • Loss of lower leg coordination or ability to balance
    • Extreme instability
    • Excessive swelling
    • Severe or stabbing pain
    • Bleeding
    • Complete loss of range of motion
    • Deformity of the knee or other areas of the leg 

    Diagnosing and Treating Knee Pain and Stiffness

    Direct injuries, medical conditions, and infections that disturb the normal structure of the joint are all causes of knee stiffness and pain and make the surrounding tissues more sensitive. Speak to your orthopedic doctor for a comprehensive assessment. Apart from a thorough physical examination, you may need to undergo imaging tests, such as an X-ray, a CT scan, or an MRI. An accurate diagnosis is necessary to determine the correct treatment for stiff knee joints.

    If neglected or improperly treated, stiffness in the back of knee joints can get worse and may put you at risk of permanent joint immobility and a decrease in your overall quality of life.

    What treatment options are right for your stiff knees will be dependent on the underlying cause, your preferences, fitness level, and more. In general, a focus on restoring joint range of motion and muscle balance is important. This can be done with exercise training, inflammation management (with modalities and drugs like ibuprofen) physical therapy, appropriate use of knee braces or sleeves, and beyond. Once you have an accurate diagnosis, the rest will fall into place for treatment so that you can start feeling your best.




    Jaydee Vykoukal, PT, DPT
    Jaydee Vykoukal, PT, DPT

    JayDee Vykoukal is a Doctor of Physical Therapy, owner of the healthy habit platform Health Means Wealth, and freelance medical writer. She loves traveling and spending time with her family in nature. Her passion is helping others continue to participate in the activities they love through education and proper exercise.

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