ACL Injuries

Tears or sprains in the ligaments of the knee can be extremely painful and can jeopardize a person’s ability to walk, exercise, or play sports normally. It is important to seek treatment for knee pain or weakness, especially if you’re an athlete or participate in high-impact physical activities.

The anterior cruciate ligament (ACL) is one of the most important ligaments in the knee, helping us enjoy a full range of motion during sports or exercise. Unfortunately, this ligament is also quite vulnerable to injury, especially among athletes.

It is vital for individuals who suspect they have damage to their ACL to seek medical treatment immediately, as this ligament does not have a blood supply and thus cannot heal on its own. Additionally, ACL injuries increase a person’s risk of developing posttraumatic osteoarthritis.

Mobility Bone & Joint Institute’s Sports Medicine program offers diagnosis and treatment of ACL sprains, tears and damage and is proud to help athletes get back to the sports they love.

Here’s what you should know about ACL injuries and their treatments.

What is the Anterior Cruciate Ligament (ACL)?

The ACL, one of two major cruciate ligaments in the knee, is made of thick, fibrous connective tissue that joins the bottom of the thighbone (femur) with the top of the shinbone (tibia).

The kneecap sits in front of the ACL to provide some protection from external forces. Together with the PCL (posterior cruciate ligament), the ACL forms an “X” shape within the knee to provide stability during pivoting or rotational movements, as well as the prevention of excessive forward movement of the tibia.

Why Are ACL Injuries So Common?

ACL injuries are one of the most common knee injuries, especially in athletes and physically active people. This is due to a number of factors, including the continuous wear and tear on the ligament during movement, as well as the complex pivoting, decelerating and rotational movements many sports require. The annual reported incidence of ACL injuries in the United States is approximately 1 in 3500, accounting for 100,000 to 200,000 injuries each year1.

Due to the physical nature of sports, athletes are far more likely to experience an ACL tear, sprain or rupture than non-athletes. Additionally, certain sports produce a higher incidence of ACL injuries than others.

Athletes playing high-demand (agility) sports are most likely to suffer anterior cruciate ligament injuries.

High-demand sports include:

  • Football
  • Soccer
  • Gymnastics
  • Basketball
  • Tennis
  • Lacrosse
  • Volleyball

The majority of ACL injuries are non-contact injuries sustained during abrupt stopping, high-impact landing and directional changes (pivoting and cutting) during play.

Rates of ACL Injury Among Males and Females

While males experience more ACL injuries overall, female athletes are more likely to sustain these injuries than male athletes.

In one study, high school girls’ soccer produced the highest rate of ACL injuries, followed by boys’ football2.

Additionally, a study from the Journal of Orthopaedics reported that high school girls were 3.5 times more likely than high school boys to sustain an ACL injury during basketball. In soccer, they were 2.8 times more likely than boys to sustain these injuries3.

Why the reasons for this disparity in injury rate are not well understood, there do appear to be certain risk factors for female athletes.

According to the American Academy of Orthopaedic Surgeons, the following nonmodifiable and modifiable risk factors are associated with an increase in ACL injuries in female athletes4:

  • Increased Q angle – The measurement of the angle between the quadriceps muscle and patellofemoral tendon is typically higher in females
  • Hormonal factors – Estrogen may have an impact on the structure of skeletal bone, connective tissue and collagen
  • Differences in muscular function and strength – Many female athletes use a deceleration pattern that relies heavily on the quadriceps. When coupled with weak hamstrings, this pattern can increase the risk of ACL injury.

Types of ACL Injuries

Over half of all ACL injuries occur in tandem with injuries to other parts of the knee, such as the meniscus, collateral ligaments and cartilage within the knee joint.

A Grade 1 ACL injury is a mild sprain (stretching) of the ligament. While a Grade 1 injury can be painful, the ligament still provides adequate stability to the knee joint.

A Grade 2 injury is a severe sprain, sometimes known as a partial tear. These injuries are rare.

A Grade 3 injury is a complete tear or rupture of the anterior cruciate ligament. A Grade III sprain causes more severe symptoms and will leave the knee joint unstable. These injuries are the most common ACL injuries to occur.

Symptoms of ACL Injuries

The most common symptoms of an ACL tear or injury include:

  • A sharp pain at the moment of injury
  • Hearing a pop or feeling a pop in the knee at the moment of injury
  • Instability in the knee joint (being unable to place weight on the knee after the injury)
  • Immediate swelling in the knee

Knee pain may become a deeper, constant ache in the hours and days after the injury. You may also develop bruising or discoloration at the site of the injury.

Diagnosis of ACL Injuries

To diagnose an ACL tear or sprain, a sports medicine doctor uses a number of examinations and tests.

If you suspect you’ve sustained an ACL injury, here’s what to expect during the diagnosis stage:

First, your doctor will perform a physical examination of your knee. This examination will check for swelling, pain points, bruising and other easily visible symptoms.

Following a physical examination, you may be asked to undergo x-rays to check for fractures in the bony structures of the knee.

You may also be asked to undergo an MRI, which checks the soft tissues, like ligaments and tendons, within the knee. An MRI will show the extent of the damage to the ACL and surrounding structures.

Treatment of ACL Injuries

Grade 1 injuries (mild sprains) can typically be treated using the RICE method:

Resting the knee, icing the area to prevent or control swelling, compressing the swelling, and elevating the injured knee.

NSAIDs like ibuprofen are typically recommended to control pain and swelling as you heal.

After the swelling and pain have subsided, your doctor will recommend physical therapy to help strengthen the muscles that surround the knee and reduce the likelihood of re-injury.

Grade 2 injuries can also be treated with the RICE method and physical rehabilitation, but some tears may require more complex treatment.

Grade 3 injuries–the total rupture of the ACL–require surgical treatment. ACL reconstruction surgery replaces your damaged ligament with your own tissues or with donor tissues.

It is extremely important for individuals with Grade 3 injuries to see an orthopaedic surgeon immediately.

ACL Injury Diagnosis and Treatment at Mobility Bone & Joint Institute

Mobility Bone & Joint Institute is the only practice in the Merrimack Valley that can diagnose diseases, infuse medications, and perform x-rays on site.

Do you have questions about the diagnosis and treatment of ACL injuries at Mobility Bone & Joint Institute?

Call (978) 794-1946 or click here to schedule an appointment at our Andover, MA office.

Call (603) 898-2220 or click here to schedule an appointment at our Salem, NH office.

  1. “Anterior Cruciate Ligament Knee Injuries – NCBI – NIH.” 10 Aug. 2020,
  2. A Multisport Epidemiologic Comparison of Anterior Cruciate ….”
  3. “The female ACL: Why is it more prone to injury? – NCBI.” 24 Mar. 2016,
  4. “AAOS Now September 2019: Mary K. Mulcahey, MD, Details ….” 1 Sep. 2019,

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