8 Common Types of Knee Injuries

Approximately 40% of all sports-related injuries affect the knee joint, making knee injuries the most common orthopedic complaint seen by injury care specialists. Moreover, nearly 20% of adults above the age of 60 will experience chronic knee pain.

Needless to say, your knees take a constant beating. From flexion to extension, pivoting, and compression, your knees absorb stress from multiple planes of movement. In order to be so mobile, the knee must possess a certain level of laxity.

However, just as a rubber band can lose its elasticity, so too can the ligaments and tendons that hold together the muscles and bones of your knee. When these structures become too mobile, it sets the stage for a knee injury to occur.

Let’s take a closer peek at the anatomy of the knee to learn why.

Examining Your (Not-So-) Basic Knee Anatomy

The knee joint is formed by the meeting of your femur (or thighbone) and your tibia (or shinbone). Your patella, or kneecap, covers and protects the joint, like a tiny helmet.

Classified as a hinge joint, your knee moves primarily backward and forward, retaining some limited flexibility for inward and outward rotation. Imagine, for example, the hinges on a door. The door primarily opens and closes, but if you apply enough force with your hands, you can still jiggle the door upward and downward in its frame.

All hinge joints contain cartilage, which lines the bones, and a viscous lubricant, known as synovial fluid. Synovial fluid coats the joint anatomy, allowing the structures to glide past one another during movement. Without synovial fluid, your bones would grind together like the components of an engine without oil. This would lead to the accelerated breakdown of the joint as well as chronic pain.

In addition to cartilage and bones, your knee contains ligaments and tendons that hold the joint together like a series of bungee cords. Ligaments connect bone to bone, whereas tendons connect muscle to bone. As we will see, many knee injuries involve damage to our ligaments and tendons, which easily pop or tear under excessive pressure.

Without further ado, here are the 8 most common types of knee injuries:

1. Anterior Cruciate Ligament (ACL) Tears

Under your kneecap, you have two ligaments that criss-cross, the anterior and posterior cruciate ligaments, aka your ACL & PCL. The anterior cruciate ligament is so named because it crosses in front of its posterior counterpart. Your ACL prevents your shinbone from sliding off the femur, leading to hyperextension.

However, sometimes, particularly during sports, such as basketball and soccer, that involve pivoting or landing, the ACL can tear. When this occurs, you may hear an audible pop in the joint accompanied by sudden swelling.

A doctor will assign your ACL injury a grade of 1-3, with grade 1 indicating overstretching, grade 2 signifying a partial tear, and grade 3 confirming a complete rip. For grade 1 and 2 injuries, nonsurgical interventions should be sufficient to ensure proper healing. For grade 3 injuries, however, surgery will most likely be required to repair the ligament and restore function.

Note: PCL injuries are rather rare and often occur as the result of multi-ligament injuries. In other words, typically the PCL is relatively stable unless another ligament tears first, increasing the PCL’s vulnerability.

2. Medial Collateral Ligament (MCL) Tears

Your medial collateral ligament (MCL) connects your femur to your tibia on the inside of your knee. Although the ligament is located toward the medial plane of your body, direct blows to the outside of the knee typically cause this type of injury. That’s because a high-impact collision to the outer knee knocks the entire joint sideways and inward.

When you tear your MCL, you may feel or hear a popping sensation. Subsequently, you may struggle to straighten your leg or notice pronounced instability in your knee joint.

Although there is some debate regarding whether MCL injuries are more common than ACL tears, or vice versa, MCL tears tend to be less serious. Usually, an MCL injury can be managed with non-operative solutions, such as physical therapy or bracing.

3. Lateral Collateral Ligament (MCL) Tears

Your lateral collateral ligament (LCL) connects your thighbone to your fibula, the narrow bone that runs parallel to your tibia. Unlike the MCL, your LCL is located on the outside of your knee.

Normally, an LCL tear occurs when a patient sustains a blow to the inside of the knee. This could occur when absorbing a tackle during football, jumping and landing improperly, or over-torquing the knee.

As with any knee ligament injury, you may experience localized pain and swelling at the site of the injury as well as an inability to straighten out the knee.

Complete LCL tears require surgery to repair; however, partial sprains often respond to conservative interventions. These may include rest, heat/ice application, supportive knee devices, or physical therapy, etc.

4. Torn Meniscus

Your menisci are two C-shaped (or semi-lunar) strips of cartilage that pad the knee joint, where the knobs of your femur meet the grooves of your tibia. Specifically, the menisci function to absorb shock during joint movement (aka, articulation).

Believe it or not, your knee absorbs up to 4x your body weight every time you take a step. Needless to say, the menisci—two primary players at the center of all the action—undergo quite a bit of wear and tear. Especially if the patient participates in sports like tennis that involve a lot of pivoting.

If you injure your meniscus, you may experience pain, localized swelling, decreased range of motion, and joint instability. In addition, a portion of the crescent-shaped cartilage may tear away, creating what is known as a bucket-handle tear. In other words, instead of resembling a C-shape, your meniscus will assume a D-shape. Sometimes, this flap of cartilage even blocks the knee joint, disrupting the knee’s normal range of motion.

Depending on its severity, meniscal tears are treated with rest, NSAIDs, conservative therapies (such as physical therapy), and occasionally, arthroscopic surgery.

5. Patellar Tendinitis

Your patellar tendon connects the bottom of your kneecap (aka, your patella) to your tibia. Despite its name, your patellar tendon is actually a ligament because it attaches two bones together instead of a muscle and a bone. The patella itself connects to your quadriceps muscles to enable the extension of your knee. Since the key function of the patellar tendon is to straighten out the leg with the aid of your quads, this may explain the misnomer.

At any rate, patellar tendinitis occurs when tiny tears appear in your patellar tendon. This can happen as the result of injury, particularly from jumping and landing improperly. (In fact, some doctors alternatively refer to patellar tendinitis as jumper’s knee.) However, certain chronic diseases (e.g. lupus, diabetes, etc.) can disrupt healthy blood flow to our tendons, leading to inherent tendon weakness.

Symptoms of patellar tendinitis include pain and swelling around the bottom of the kneecap, knee buckling, or displacement of the kneecap. The primary nonsurgical treatment method for addressing patellar tendinitis is physical therapy, but your injury may require surgical tendon repair, especially if the kneecap becomes unmoored.

6. Knee Fractures

Speaking of the patella, a knee fracture occurs when this tiny, misshapen sphere of bone sustains a break. A knee fracture can range in severity from minuscule cracks to complete breaks in the patella that lead to the displacement of the kneecap. Often, these injuries result from slip and fall accidents onto the knee or dashboard-to-knee blows during a car accident.

As with other broken bones, you may experience swelling and bruising around the kneecap. With more unstable fractures, you may even temporarily lose your ability to walk. Generally, the healing process will involve wearing a supportive cast and limiting the amount of weight you apply to the leg. However, fractures involving kneecap displacement often require surgery to reattach the kneecap to the appropriate tendons, etc.

7. Knee Dislocations

We’ve already discussed kneecap (or patella) dislocations several times thus far. However, knee dislocations involve displacement of the femur where it meets the tibia. These injuries, while exceedingly rare, tend to be incredibly dangerous. In fact, a knee dislocation can even lead to loss of the limb.

Most often, knee dislocations occur as the result of extreme hyperextension. This can happen in the context of a high-velocity accident (such as a fall from a considerable height) or a low-velocity collision (e.g. an athletic injury).

Needless to say, this injury doesn’t manifest in subtle ways. The knee joint appears grotesquely deformed following the accident and immediate swelling and bruising will develop, causing severe pain. In addition, some knee dislocations result in serious collateral damage, such as nerve compression, arterial tearing, or blood clot formation.

Almost universally, your doctor will opt for surgery. A number of techniques may be used depending on the anatomical structures involved. For example, you may not only require open surgery to realign and secure the bones but also, arterial and cartilage repair.

8. Knee Bursitis

The human body contains approximately 140 bursae, tiny fluid-filled sacs that resemble water balloons. These flexible sacs serve as cushions between high-friction areas of bony anatomy and connective tissue within our moveable joints.

In the knee, for example, the prepatellar bursa serves as a cushion between your kneecap—at the most highly bendable part of the knee joint—and your skin. However, all told, there are 30 different bursae in your knee that can become inflamed.

An inflamed bursa often produces a visible lump where swelling occurs. In addition to pain, the knee may feel stiff or difficult to bend. If the bursitis is being caused by infection, the knee may feel warm to the touch and the patient may spike a fever. In particular, a fever from bursitis could signify sepsis and should be regarded as a medical emergency.

If you’ve been diagnosed with bursitis, you may be able to manage your condition with at-home methods such as rest or anti-inflammatory medications. Your doctor may treat moderate cases of bursitis with cortisone injections or bursal aspiration (i.e. fluid removal via needle drainage). More serious cases of bursitis may require antibiotic therapy or surgical removal of the bursa altogether.

Reclaim Your Life from Chronic Knee Pain

Like back pain, knee injuries are difficult to ignore. Luckily, you don’t have to.

At the Injury Care Center, our multidisciplinary team of experts consists of award-winning pain management specialists, physical and occupational therapists, chiropractors, and licensed massage practitioners. We employ a multi-modal approach to ensure that you receive the finest standard in injury care. After all, you deserve the same access to cutting-edge equipment afforded to elite athletes.

With over 30 years of experience, we invite you to find out why our pain management experts are consistently rated the best doctors in Pennsylvania (and the United States)!