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Common Knee Injuries and Conditions

We’ve all done something to our knees, whether it’s knocking them into the coffee table, twisting them while playing sports, or experiencing seemingly random pains during daily activity like climbing or descending stairs. Most of our aches and pains disappear over a few days, but what about the ones that linger?

This blog post is dedicated to various knee injuries and the aches and pains that don’t disappear. If you haven't had a chance yet, check out my blog post Understanding Knee Mechanics for pictures and a description of the structures in and around the knee.

A quick word on how ligament, muscle and tendon injuries are graded. A grade 1 tear refers to a stretching of tissue and an insignificant amount of muscle or ligament fiber tear, typically <5%. Grade 2 tears involve 5 – 99% of fibers torn. Grade 3 tears involve complete rupture of all fibers. Clinically, a grade 1 ligament tear does not result in laxity and has a firm end feel but may be painful. A grade 2 ligament tear results in some laxity, but a firm end feel remains. A grade 3 ligament tear results in significant non-biological movement due to the absence of an intact ligament and thus lacks end feel. Grade 3 ligament tears result in structural instability and often require surgical reconstruction.

Chondromalacia Patellae (Runner's Knee)

This injury or condition is often referred to as “runner’s knee” due to its high prevalence in running athletes. It refers to softening of the hyaline or articular cartilage on the posterior aspect of the patella. While common in running athletes, this is also common in individuals with osteoarthritis. Similar to patellofemoral pain, an increase in friction between the patella and femur (in this case due to decreased cartilage) can contribute to pain at the front of the knee.

General Knee Instability

Two types of knee instability exist: structural instability and functional instability.

  • Structural instability is where a passive structure in the knee, either a ligament, joint capsule, or meniscus is partially or completely torn and thus allows a non-biological movement to occur and and the feeling of a knee that might suddenly move in an unintended and unnatural direction. Click here for more details on the structures of the knee.

  • Functional instability is where muscles are not capable of controlling knee movement as they should either due to pain mediated inhibition, muscle tear, or muscle weakness. Pain mediated quadriceps inhibition is the most common cause of functional instability and manifests as knee pain that causes the brain to ‘turn off’ the quadriceps muscles momentarily, resulting in the knee popping forward as the knee flexes, which is met with a sudden reactive quadriceps activation to stop the knee from flexing and prevent a fall. This pain mediated quadriceps inhibition can occur due to pain from osteoarthritis, patellofemoral pain, IT band friction syndrome, quadriceps or hamstrings muscle pain, and any kind of knee surgery.

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Iliotibial Band Friction Syndrome (ITBFS)

The IT band runs down the lateral side of the thigh and inserts into the lateral tibia. As the name of the condition suggests, it can cause friction, typically on the lateral femoral epicondyle, that results in some inflammation and localized pain. This friction occurs at ~30 degrees of knee flexion as the IT band flips from being anterior to the lateral femoral epicondyle to being posterior to it.

Contrary to popular belief, it is not possible to stretch the IT band, however it is possible to release the underlying quadriceps muscle and tensor fascia latae (TFL), which will both reduce the pressure on and tension in the IT band. This, combined with changing mechanics during activity can take pressure off the lateral femoral epicondyle, reduce the friction and allow this condition to resolve.

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Ligament Tears

Although any of the ACL, PCL, MCL or LCL can be torn, the most commonly injured are the ACL and MCL, often in conjunction with each other. These injuries are typically the result of sports activities involving a direct hit or a sudden change in direction, but also occur during falls and car accidents.

Complete tears of knee ligaments result in structural instability that result in a feeling of an unstable or wobbly knee. Surgical reconstruction is often necessary to regain stability and is particularly important if one wishes to push their personal limits with sport and activity.

Meniscus Tears

During plant and twist type motions of the knee, especially in high impact or high speed sports, the menisci can be pinched between the femur and tibia and tear. Meniscus tears often happen in conjunction with ligament tears due to the high forces and abnormal movement involved in these injuries. Menisci have poor blood supply and do not heal well. A tear in the outer 1/3 of the meniscus may heal slowly over time, but this ability decreases as we age. Fortunately, only this outer 1/3 of the meniscus appears to have nerve endings and so a tear of the inner 2/3 typically goes unnoticed. Meniscus tears are most bothersome when a piece of the torn meniscus twists on itself and causes locking of the knee. This twist can spontaneously resolve, but if the tear is large enough it may require surgical resection.

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Although not a specific injury per se, osteoarthritis refers to a degeneration of the articular cartilage, and in advanced cases the degeneration of the underlying bone. Osteoarthritis most commonly affects the medial compartment of the tibiofemoral joint and can contribute to joint pain and stiffness.

The Osteoarthritis Research Society International (OARSI) has published a list of non-surgical guidelines recommending biomechanical intervention, gait aid (cane), exercise (land, water, or strength training), physician prescribed medication, and weight loss for management of knee osteoarthrtitis pain and function 1. Physiotherapy is most effective for biomechanical intervention, recommending gait aid, and recommending appropriate exercise. Despite all the options for people with osteoarthrtitis, OARSI found that the most effective treatment was weight loss of 5% of total body weight over 20 weeks 2.

Patellofemoral Pain

This refers to pain originating around or behind the patella, due to dysfunction or overuse at the patellofemoral joint. Typically, this pain is caused by poor tracking of the patella due to muscle imbalance and can lead to inflammation between the patella and femur. Physiotherapy treatment consists of stretching and lengthening muscles, changing movement patterns, and strengthening designed to reduce pain and inflammation around the patella.

Patellar Tendinopathy

This refers to an overuse injury of the patellar tendon. This is common in jumping athletes and is therefore often referred to as “jumper’s knee”. Depending on the type or severity of injury to this tendon, pain can be felt through the length of the tendon or localized at the tendon's insertion on the tibia. Patellar tendinopathy is more common in younger people who are growing or engaging in high intensity jumping activity.

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If you’ve had a knee injury and you’re struggling to understand it or recover from it, book an appointment today so we can help you set the stage for fast healing and quick return to your usual activities.


  1. McAlindon, T E, et al. OARSI guideines for the non-surgical management of knee osteoarthritis. Osteoarthritis and Cartilage. 2014;22(3), 363-388. doi:10.1016/j.joca.2014.01.003

  2. OARSI Non-surgical management of knee osteoarthritis: Patient summary. Published March 4, 2014. Accessed October 15, 2019.

Stephen Baker graduated from Western University with a Masters of Physical Therapy. He has a passion for helping those with neck, hand or knee injuries return to their daily adventures. Book with Stephen today.

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