When your child plays sports, you expect a few bumps and bruises. But a sudden knee injury can feel different — and scary. One minute your child is running down the field. The next, they are on the ground holding their knee.

An ACL injury is a serious sports injury in young athletes. And they are happening more often than ever before.

Here is what you should know — from warning signs to treatment options — and why specialized pediatric care matters. 

What Is an ACL?

The anterior cruciate ligament, or ACL, is a strong band of tissue inside the knee that connects the thigh bone (femur) to the shin bone (tibia). It helps keep the knee stable when the body twists, turns and pivots.

ACL Injuries Are Rising

In teenage and high school athletes, knee injuries make up about 50 to 60% of acute sports injuries. And ACL tears are a leading injury. They’re more common than before for two reasons:

• Early Sports Participation: Children today start organized sports at younger ages. And seasons run longer. The more a child does movements that rely on the ACL, the greater the chance of injury.
  
  
• Early Sports Specialization: In the past, many children rotated between different sports throughout the year. Many kids now focus on one sport year-round. Repeating the same movements without seasonal breaks or cross-training can also cause strain on the ACL.

Movements Causing ACL Injuries

Many people assume ACL injuries are caused by contact. In reality, 70% are noncontact injuries — meaning they happen without another player involved. A child can tear their ACL simply by

• A sudden stop
• Changing direction
• Landing from a jump
• Pivoting quickly

ACL Injury Risk Factors

Size, strength imbalances and gender can influence ACL injury.

1. Anatomy factors: Smaller ligament size or a narrower space in the knee where the ACL sits can contribute to tears.

2. Strength imbalances: Stronger quadriceps and weaker hamstrings cause strength imbalances impacting the ACL.

3. Gender: Girls are at a slightly higher risk than boys due to a number of structural, hormonal, and environment factors.

In female athletes, ACL tears are most common in soccer and basketball. For male athletes, football leads the list because it includes both contact and non-contact movement. Soccer and basketball follow closely behind.

Signs Your Child May Have an ACL Tear

If your child hurts their knee, watch for warning signs:

• Noticeable swelling: When a child has swelling after an acute knee injury, about 80% of the time there is damage inside the joint.
  
  
• Feeling fluid in the knee: The knee may look puffy or feel tight and full. Fluid or blood built up inside the joint after the injury causes this.
  
  
• Pain with movement: Your child may feel pain when bending, straightening or turning the knee. Pain that gets worse with movement can be a sign of a more serious injury.
  
  
• Hearing a pop: Some kids hear or feel a pop during injury.

If your child cannot put weight on the leg or has severe pain, urgent care or the emergency department may be needed. If pain is manageable and they can walk, contacting your primary care provider or a pediatric sports specialist within a day or two is reasonable.

Diagnosing ACL Injuries

Providers can often suspect an ACL tear during a physical exam but swelling and muscle guarding can make the knee difficult to assess. In most cases where there is swelling inside the joint, an MRI is ordered to confirm the diagnosis and check for additional injuries. For example, if your child can’t put weight on the leg or has severe pain, there could be a fracture or kneecap dislocation.

The MRI helps determine whether the tear is and what the treatment plan will be:

• Complete
  
  
• Partial
  
  
• Associated with cartilage or meniscus damage

Does Every ACL Injury Need Surgery?

Not every ACL injury needs surgery. No matter the approach, the goal is to stabilize the knee. If the ACL is only partly torn and the knee is still stable, physical therapy and a brace may be enough to help it heal and get stronger.

Surgery is recommended for most complete ACL tears. Without a stable ACL, the knee can repeatedly give out. The instability increases the risk of long-term cartilage and meniscus damage.

What ACL Surgery Looks Like

ACL surgery is usually an outpatient procedure. Your child will go home the same day of the surgery. Prior to operating, the surgeon will wait for swelling to go down and for your child to regain appropriate range of motion. For this reason, surgery might not be immediate.

The surgeon will typically reconstruct the torn ACL using graft tissue from another part of the body to create a new ACL ligament. Grafts most often come from the:

• Quadriceps tendon (Quad)
  
  
• Hamstring tendons
  
  
• Patellar tendon (BTB)

In children and teens, surgeons must protect the growth plates. Using adult surgical techniques on a growing child can damage those plates and affect bone growth — which is why pediatric expertise is so important.

Experts in the Children’s Wisconsin Orthopedics Program are highly trained in assessing bone age and growth plate status to choose a safe and effective surgical approach.

Recovery Takes Time — and Support

At Children’s Wisconsin, orthopedic specialists and surgeons, physical therapists and sport psychologists work together to minimize complications, protect growth, support recovery and reduce reinjury risk.

ACL recovery takes time. After surgery:

• A brace is worn for about six to eight weeks
  
  
• Crutches are often needed at first
  
  
• Physical therapy begins within a few days

Running typically starts around three to four months. Higher-level activities such as jumping and cutting begin closer to six months. Most athletes are not cleared to return to sports until at least nine months — and only after strength and functional testing show they are ready.

Recovery is not just physical. Being away from teammates, missing school for appointments and worrying about reinjury can take a mental toll. Support from sport psychologists can make a meaningful difference during this time.

While an ACL injury is serious and the recovery long, with early care and coordinated pediatric care, your child can heal, rebuild strength and safely return to the activities they love.