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Sprained Knee Injury

by Jaydee Vykoukal, PT, DPT October 07, 2020 0 Comments

Fastening knee brace

Even if you have already made an appointment to get your sprained knee injury checked out by a doctor, you can get started on the road to full mobility today in your own home. However when it comes to soft tissue injuries, the recovery process requires more than an ice pack and massage. Healing faster, more thoroughly, and reducing the risk of future injury takes an in-depth understanding of the sprain itself, followed by appropriate treatment.

What is a Sprained Knee Ligament?

Being able to tell if you sprained your knee is often a matter of understanding all the moving parts and how they work together to keep your knee joint stable and in motion. The knee is made of three main bones—the femur, tibia, and patella—as well as an abundance of tendons, cartilage, other soft tissues. A sprain is classified as damage to these soft tissues.

As one of the most complex joints in our body, it shouldn’t be surprising that a sprained knee ligament is both common and costly. The ligaments both support and guide the bones, allowing us to walk, run, and jump efficiently. Sprains make such motion difficult, potentially unstable, and even painful.

Types of Sprained Knees

There are 4 primary ligaments that provide robust stability in the knee. They work together to provide support in every possible direction the knee moves. With high impact injuries, it is highly likely that more than one ligament and other surrounding tissues, like the joint capsule or menisci, will be affected. 

  • ACL

    Anterior cruciate ligament (ACL) sprains account for almost half of all knee sprains, a damaged ACL is by far the most commonly sprained ligament in the knee. The ACL is the core stabilizing ligament in the center of the knee, connecting the back of your thigh bone to the front of your shin bone. Sprains are most often caused by sudden twisting or hyperextension.

  • PCL

    Providing complementary and opposing stability to the knee from the ACL is the posterior cruciate ligament (PCL). The PCL ligament is another crucial part of a healthy knee connecting the front of the thigh to the back of the shin bone. PCL tears are much rarer and typically only occur in car accidents or really high impact injuries. 

  • MCL

    The medial collateral ligament (MCL) provides inner stability to the knee. With a sprained MCL, the knee is damaged by a sudden force on the outer portion of the joint that strains the inside of the knee. The tendon itself links the thigh bone to the shin bone on the inner side of the leg. Exterior force may bend the entire joint inward, resulting in a stretched or torn MCL ligament.

  • LCL

    The lateral collateral ligament (LCL) provides complimentary stability to the outside of the knee- opposite of the MCL. An LCL sprain occurs when a force pushes the knee joint outward, stretching or tearing the tendon. The job of the LCL is to connect the thigh bone to the fibula, a smaller bone in the lower leg.

Sprained Knee Grades

Aside from the location of the injury and the specific ligament damaged, sprained knees are classified by their severity, on a scale of one to three. Your sprained knee pain will vary greatly depending on the grade.

  • Grade 1

    An injury that tears 10% or less of the fibers in the ligament.

  • Grade 2

    Anywhere between 11% and 90% of the fibers can be torn.

  • Grade 3

    A complete rupture, which requires the longest and most difficult sprained knee recovery.

Common Causes of a Sprained Knee

A sprained knee ligament of any kind results from two main causes.

1. Direct Impact

First is a direct impact to the knee, either from a car accident, a fall, or another person. The angle of impact is the main factor that determines the type of injury, whether a sprained MCL knee or any of the other varieties.

2. Sudden Movement

The second common cause is a sudden and unnatural movement, which can pull or twist the ligament in ways it is not meant to move or beyond its normal strength. One of the clearest signs of a sprained knee is such a movement accompanied by an audible popping noise.

Other Causes

While sprained knees are most commonly caused by accidents similar to those described above, there are a number of contributing factors that make a fall or crash even more dangerous.

  • Arthritis

    Whether your joint pain is caused by decades of wear and tear or a spontaneous autoimmune reaction, arthritis increases the likelihood of spraining the knee. Arthritis can affect the joint’s stability and make injury more likely with uncoordinated movements due to loss of strength and function. 

  • Previous Injury

    Have you suffered a leg or knee injury in the past? Whether minor or severe, a previous injury makes future sprains even more likely. In addition, previous sprains could mean a longer recovery time.

Sprained Knee Symptoms

With any knee injury, it can be hard to differentiate which area was injured and whether you sustained a tear. Regardless of what tissues were damaged, it typically leaves most patients at least partially immobile for days or weeks. What are the symptoms of a sprained knee?

  • Tenderness and pain along the affected ligament (palpable with an MCL or LCL injury)

  • Sprained knee swelling that usually impairs knee range of motion

  • A sensation of “locking” in the knee due to significant muscle stiffness and guarding

  • Difficulty or inability to put weight through the injured leg

  • Varying degrees of instability in the knee when trying stand on it

Keep in mind that symptoms vary slightly depending on the exact ligament that is sprained and the severity of the sprain.

Common Questions About Knee Sprains

  • What Does a Sprained Knee Feel Like?

    Recognizing a sprained knee can be challenging because of the similarities in symptoms to conditions like arthritis or muscle strain. However, one of the telltale signs of a sprained knee is a feeling that the leg will give out when you stand. If the joint is painful but stable, it may not be a sprain.

  • What Does a Sprained Knee Look Like?

    Knee sprains are not known to cause physical deformity, but they can be visually identified by swelling in the area. More serious sprains may present bruising.

  • Can You Walk on a Sprained Knee?

    That depends on the severity of the injury. A sprained knee tendon can be a minor injury that clears up in a few days (or weeks) or a serious tear that requires surgery. You can usually walk on a sprain if necessary, but crutches,  hinged braces, and other aids are used to speed recovery initially. 

  • Diagnosing a Sprained Knee

    Ultimately, a professional evaluation can help give you clarity on what type of injury you have sustained. During a physical, your doctor will gently bend the knee and apply pressure at various points. 

    Based on your response, they will be able to tell which specific ligaments are damaged. If they suspect more severe damage, they may use tools like an MRI or further physical examination to determine what grade of tear the injury is.

Sprained Knee Recovery Time

Recovery time for sprained knee can take days, weeks, or several months, depending on the severity of the injury. If symptoms remain after a week of home treatments, consult your doctor.

The other factor to consider while healing a sprained knee is the type of sprain. MCL and LCL sprains tend to heal the most quickly, at two to four weeks for grade 2 sprains. Severe sprains can take four to twelve months to heal and require significantly more rest time.

Great ways to expedite the recovery program include home treatment for addressing pain and swelling, use of a brace, and seeing a physical therapist. If you undergo surgery, physical therapy will be a must to get you back on track. No matter how minor or severe the injury is, knowing how to treat it can boost your recovery process.

Making a Full Recovery

Anyone going through sprained knee rehab will know that a full recovery is not an easy road. Only through a combination of regular exercise, healthy diet, and appropriate treatment can sprained knee healing time be kept to a minimum. With consistent and quality care to restore stability in the knee, even a severe sprain can be made manageable.


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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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