Overview of Common Knee Injuries

By: | Tags: | Comments: 0 | September 30th, 2019



What Is a Knee Ligament?

Four ligaments stabilize the knee and consist of thick bands of tissue. The lateral collateral ligament (LCL) and medial collateral ligament (MCL) prevent the joint from moving side to side, while the posterior cruciate ligament (PCL) and the anterior cruciate ligament (ACL) prevent the knee from sliding backward or forward.

Overview of Common Injuries & Causes

Unfortunately, injuries to the knee occur quite frequently. Some of the most common causes of knee pain include muscle strains, ligament sprains, arthritis, biomechanical dysfunction, Osgood-Schlatter disease, and referred pain stemming from sciatica.

Other parts of the knee that may become injured include the cartilage (menisci) or broken bones within the joint itself. Since knee pain
has many causes, an accurate diagnosis is essential to creating an appropriate treatment plan that is specifically designed to address the knee injury or condition causing the pain.

ACL – Anterior Cruciate Ligament

An ACL injury typically occurs from a sudden twisting or cutting motion, which causes the anterior cruciate ligament joining the femur and tibia to tear. ACL tears can range from small (which causes mild pain) to a complete tear or the detachment of the ligament and a portion of the bone from the rest of the bone (which causes severe pain).

Following any injury to the ACL, seeking treatment is vital. Once injured, the ligament’s ability to control the movement of the knee decreases and the likelihood of the bones rubbing against one another increases. This is referred to as chronic anterior cruciate ligament deficiency. If

the bones begin moving irregularly, the tissue covering the ends of the bones may suffer damage. If this happens, the pads that are meant to cushion the knee joints may tear or become trapped and can lead to osteoarthritis.

PCL – Posterior Cruciate Ligament

The posterior cruciate ligament (PCL) is similar to the ACL, as it connects the femur to the tibia, however strains and tears are less common due to the mechanism of injury. The PCL is put under the most tension when the knee is bent and an anterior force is applied, therefore tears are most common in car accident victims. When PCL tears do occur, typically physical therapy is used first in attempt to strengthen the knee musculature before the possibility of surgery.

MCL – Medial Collateral Ligament

The medial collateral ligament (MCL) is located on the inner side of the knee. It connects the medial tibial condyle and the medial femoral condyle. The MCL consists of strong fibrous connective tissue that
is composed of stringy collagen molecules. The medial collateral ligament’s primary function is to prevent the knee from over-extending inward, but also provides stability and allows the knee to rotate.

An MCL injury occurs when the ligament itself is overstretched. This can occur when the knee rotates while the foot remains fixed, such as quickly changing direction, landing incorrectly following a jump, or a blunt force trauma to the knee. Incoordination or muscle weakness make an individual more prone to suffer a ligament sprain or tear.

LCL – Lateral Collateral Ligament

The lateral collateral ligament (LCL) is located on the outer side of the knee. This cordlike ligament forms part of the posterolateral corner
of the knee. The LCL originates from the lateral femoral epicondyle, joining the bicep femoris tendon before it attaches to the fibula. The LCL helps stabilize the knee joint, and sustains injury when the force is too great and the ligament is overstretched. The most common injury to

the lateral collateral ligament is a sprain. The majority of injuries to this ligament occur in conjunction with damage to other parts of the knee (e.g., meniscus, ACL, etc.).

The LCL’s main function is to resist the varus force and rotation of the shin bone, which occurs when the tibia/foot is forced inward. This injury can occur during an incorrect landing technique when the foot is fixed, and the knee twists medially due to a blunt force or hyperextension of the knee. Similar to the MCL, muscle weakness or incoordination can make an individual more likely to suffer a sprain or tear.

Symptoms & Severity of Injury

The symptoms experienced depends on the degree of tearing or stretching the ligament has sustained.

  • A grade I sprain is the mildest form of the injury – The ligaments are overstretched; however, they are not torn. While this injury may not cause very much swelling or pain, it can increase the likelihood of an individual experiencing another ligament injury in the future.
  • A grade II sprain is a moderate injury – The ligament is torn to some degree. Bruising and inflammation is expected, as well as difficulty using the knee; when movement is attempted, pain is increased.
  • A grade III sprain is the most severe form of a ligament injury –

The ligament is completely torn. Inflammation, bruising, inability to bear weight, and instability are the symptoms associated with a severe ligament sprain. Many times, pain is absent following a grade III tear because the pain fibers were also torn at the time the injury was sustained.


The stability, tenderness, and movement of both knees will be evaluated. X-rays and/or a MRI may be ordered to check the bones, tendons, ligaments, knee cartilage, and muscles. An arthroscopic procedure may also be performed; during this procedure, the physician creates small incision(s) in the knee and uses surgical tools to view the inside of the knee.


Again, an accurate diagnosis is essential when creating a treatment plan. Treatment plans may include:

  • Knee mobilization techniques • Taping
    • Massage
    • Strengthening exercises

RICE Method

Directly following the injury, first aid must be initiated. The goal is to reduce swelling and pain. The RICE method is the initial treatment for injuries to the knee.
R – Rest

I – Ice
C – Compression
E – Elevation
Ice should be applied to the knee in 20-minute intervals, at least three times a day. Ice should never be placed directly on the skin. Ideally, use an ice pack or a bag of frozen vegetables that can be placed across the knee. Compression helps to decrease swelling, however it is important that the wrap is not too tight. To ensure proper blood flow, after wrapping the knee, squeeze the nail bed on your toes and ensure the color returns to the area.


The RICE method should be used during the acute phase of the
injury. Other nonsurgical treatments frequently used following a
knee injury are physical therapy (i.e., strengthening exercises and electrical modalities), a weight-bearing brace or hinged knee brace, instruction on knee mobilization techniques, and medication to reduce inflammation and address knee pain.


When necessary, surgical intervention may include knee replacement or reconstruction. The procedure, recovery time, and post-surgery plan are all dependent on the injury and its severity.




The Anatomy of the Knee

The knee is comprised of the femur, tibia, fibula, and patella, which are all connected to the leg musculature with tendons. The ligaments join the bones together and provide stability. There are two pieces of cartilage located between the femur and the tibia that act as shock absorbers; these C-shaped cartilage pieces are the medial and lateral menisci. There are also numerous fluid-filled sacs, called bursae, that allow the knee to move smoothly.

Dislocation/Subluxation of Patella

This is a temporary condition in which the patella moves from its original position (in the groove between the femoral condyles) to a position on the medial or lateral side of the knee.

Patellofemoral Pain

While patellofemoral pain syndrome usually occurs in people who participate in sports, this condition can occur in individuals who are nonathletes. This syndrome can be caused by overuse, improper patella alignment, and excessive training. The stiffness and pain associated with this condition can make kneeling down, climbing stairs, and performing other daily activities difficult. Treatments include decreased activity levels or a therapeutic exercise program.

Patellar Tendonitis

This condition refers to inflammation of the tendon connecting the patella to the tibia. The pain can be mild or severe, and occurs as repetitive stress on the knee causes tiny tears in the tendon. This injury frequently occurs in athletes who participate in basketball and volleyball.

Factors that contribute to this injury include:

  • Misalignment of the ankles, feet, and legs • Tight leg muscles
    • Obesity
    • Uneven strength in the leg muscles
  • Hard playing surfaces
    • Wearing shoes that do not have sufficient padding • Chronic diseases known to weaken the tendon

Pre-Patellar Bursitis

Bursae are jelly-like sacs that are located in the joints throughout the body, including the knee. They are positioned between the bones
and soft tissues to help reduce friction. Pre-Patellar bursitis refers to inflammation of the bursa located in the front of the patella. This occurs when the bursae become irritated and the bursa begins to produce excess fluid. This excess fluid causes inflammation, placing pressure on the other parts of the knee.

Symptoms & Severity of Injury Patellar tendonitis symptoms include:

Tenderness, pain, inflammation, and burning sensation at the base of the kneecap. Pain worsens significantly upon kneeling or squatting. Initially, the pain may be sporadic, however, as the damage to the tendon increases, the pain does as well. Eventually, the pain will begin to interfere with daily activities, including sitting in a vehicle and climbing a staircase.

Knee Bursitis symptoms:

Inflammation, pain, and warmth are common symptoms of this injury, which is typically caused by overuse.


A physical exam will be performed, which may include the drawer test and the valgus stress test. Imaging tests may be ordered. These tests can include X-rays and/or an MRI. Arthroscopy and/or arthrocentesis of the knee may be recommended.


The RICE method is used to treat acute knee injuries and conditions:


Patellofemoral pain syndrome can be prevented by:

  • Wear appropriate shoes when participating in physical activities.
  • Warm up before performing any physical activities.
  • Increase training gradually.
  • Incorporate flexibility exercises and stretching techniques for the hamstrings and quadriceps into warmup routines.
  • Stretch following physical activity.
  • Avoid putting additional stress on the knees by maintaining a healthy weight.
  • Reduce or avoid any activities that have caused knee pain or injury in the past.

Prevent patellar tendonitis by:

  • Strengthen the thigh muscles.
  • Do not continue participating in an activity if knee pain is present.

Instead, stop the activity, rest and ice the knee. Continue this regimen until the pain dissipates and then avoid activities known to put additional stress on the patellar tendon.

  • Use proper body mechanics. When starting a new sport, consider taking lessons. If using unfamiliar exercise equipment, follow the instructions, and if participating in a new activity, do a bit of research to learn more about it.

Bursitis prevention by:

  • Rest knees by regularly stretching the legs, or consider switching activities periodically to avoid putting stress on the knees for an extended period of time.
  • Always wear knee pads when kneeling or participating in contact sports (e.g., basketball, football, wrestling, etc.).
  • Following a workout, apply ice and elevate the knees.



What Is the Meniscus?

The meniscus is a fibrocartilaginous structure that sits between the bones of each knee to disperse friction during movement. Each knee has two menisci: the lateral meniscus (outside) and medial meniscus (inside). The meniscus protects the thin cartilage covering the ends of the femur and tibia by serving as a shock absorber. This thin cartilage allows the knee to straighten and bend effortlessly. The meniscofemoral ligament attaches the menisci to the tibia bone; this strong tissue also provides blood to a small section of the meniscus.

Overview of Common Injuries & Causes Meniscus Tears

One of the most common injuries is a meniscal tear. The menisci balance the weight across the knee, which provides stability. When the meniscus is torn, the knee becomes unstable.

Discoid Meniscus

A healthy meniscus is shaped like a crescent moon. However, some people have a meniscus that is shaped like an oval or a disc, which
is referred to as discoid meniscus. Individuals who have these thick, abnormally shaped menisci are more likely to sustain a meniscus injury because of their malformation.

Three Types of Discoid Menisci:

  • Incomplete – The meniscus is somewhat thicker and wider than usual. • Complete – The meniscus is completely covering the tibia.
    • Hypermobile Wrisberg – The meniscofemoral ligament is absent. In

this case, even a relatively normal shaped meniscus can slip, causing knee pain as well as popping and locking.

Discoid meniscus injuries frequently occur during a twisting motion
(i.e., changing direction quickly or pivoting) or hyper-flexing of the knee.

Symptoms & Severity of Injury

While the cause of discoid meniscus is unknown, it is a congenital defect. Individuals who are born with discoid meniscus may experience symptoms without any mechanism of injury.

Typical symptoms of discoid meniscus or a torn discoid meniscus include:

  • Inflammation
  • Pain
  • Popping, catching, or locking of the knee
  • Stiffness
  • Inability to straighten the knee all the way
  • Feeling as if the knee “gives way”

Severity of Injury

  • A minor tear – Slight pain and inflammation.
  • A moderate tear – Pain in the center or at the side of the knee.
  • A severe tear – Pieces of the meniscus may move into the joint

space, causing the knee to pop, catch, or lock.


A physical exam will be performed focusing on range of motion, which may include the valgus stress test, drawer test, among others. During these tests, the physician will bend, straighten, and rotate the knee. The physician may also order imaging tests, which can include an ultrasound, MRI, and X-rays. Arthrocentesis and/or arthroscopy of the knee may also be recommended.


A physical exam will be performed focusing on range of motion, which may include the valgus stress test, drawer test, among others. During these tests, the physician will bend, straighten, and rotate the knee. The physician may also order imaging tests, which can include an ultrasound, MRI, and X-rays. Arthrocentesis and/or arthroscopy of the knee may also be recommended.

RICE Method

The RICE method is used to treat acute knee injuries and conditions:


If placing full weight on the knee is painful, avoid doing so. Nonsteroidal anti-inflammatory medications (NSAIDs) may be used to reduce inflammation and decrease pain. Physical therapy may be prescribed to reduce pain, increase the knee’s stability and improve mobility.


If the knee neglects to respond to conservative treatment, surgical intervention may be recommended. Arthroscopic surgery can be used to trim away or repair the damaged portions of the meniscus. During this surgery, several small incisions are created around the knee, and a tiny camera (arthroscope) and the tools necessary to perform the surgery are inserted through these incisions. Following surgery, most patients receive crutches and are permitted to return home. Several days after surgery, physical therapy will begin.


Injuries to the meniscus may be prevented by:

Using proper form while engaging in physical activities and exercising.
Incorporating stretching and warmups into exercise routines and prior to physical activity.

Using appropriate gear (e.g., shoes designed for the activity). Taking time to learn the proper techniques for activities before starting them.
Making sure footwear is properly laced.