With an ACL tear, typically the knee gives out, and the athlete hears a pop and collapses in severe pain. Most athletes with an ACL tear cannot resume play and must be helped off the field or court. The knee usually swells very quickly.

If an ACL tear is suspected the patient needs to see a doctor immediately. In many cases a trip to the Emergency Room is needed. You can help prevent an ACL tear with proper form and strengthening exercises. 

Learn more about ACL tears.

Articular cartilage is the shiny cartilage lining joint surfaces. This is a special type of cartilage that doesn't always heal well on its own.

Injuries to the cartilage can result in build up of scar tissue or worse bone-to-bone injury.

If your doctor suspects an articular cartilage injury, he or she may order an MRI to better evaluate the injury. Articular cartilage injuries can result in need for surgery. 

Bursitis is an inflammation of a bursa in the body. Bursas are lubricated fluid filled sacs throughout the body that help reduce rubbing, friction, and irritation between bones and soft tissue.

Bursitis is caused by direct trauma to the bursa or by a repetitive, minor impact to the area. When irritation is applied to the bursa, extra fluid fills into the bursa to cause the bursitis.

Most incidents from an acute bursitis occur from a hard hit to the area with immediate pocket swelling. Chronic bursitis, however, occurs over a long period of time with repetitive use and friction to an area.

You should call the doctor if the swollen area becomes red or warm, or if the swelling has not decreased in over a week. 

Learn more about bursitis. 

Exertional compartment syndrome is a painful condition where pressure builds up in the lower leg. There are four compartments in the lower leg with the outer (lateral) compartment being the most common.

Pain typically builds up during running and resolves with rest. The pain is often so bad that children have to stop their sport because of the pain.

Often, physical therapy and learning to run optimally can fix exertional compartment syndrome. In rare cases, surgery can be performed to fix the condition. 

The iliotibial band (IT band) is the thick band of tissue (fascia) that runs parallel to the femur, from the upper most portion of the hip bone, down the outside of the thigh, crossing the knee joint, and attaching to the top part of the tibia or shinbone.

IT Band syndrome is an overuse injury and the most common cause of outside (lateral) knee pain in runners, cyclists, and athletes who are repeatedly in the squatting position.Symptoms may include persistent swelling, redness, warmth to the touch, and pain not relieved with rest, ice, compression and elevation.

You should call your doctor if you are having ongoing lateral hip, thigh, or knee pain with physical activity and exercise. 

Jumper’s Knee can develop in athletes who do repeated jumping as in basketball or volleyball and is also common in runners. The patellar tendon is a thick band of connective tissue that connects the knee cap to the shin bone. It can become irritated and inflamed with overuse or misuse, and this causes pain on the surface of the knee.

Pain from jumper’s knee gets worse over time. You may start with pain only at the beginning or end of activity and progress to having pain with any activity involving running jumping and squatting including using stairs or sitting in a chair.

If you think your child has jumper’s knee, the first steps are rest and ice. Long term, a trip to the doctor for diagnosis, braces, and physical therapy is often needed.

Learn more about jumper's knee.

The Medial Collateral Ligament, or MCL, is one of the four main ligaments that make up the knee joint. The MCL is a broad, thick band that runs down the inner part of the knee, from the femur to about four to six inches from the top of the tibia.

Injury to this ligament generally occurs when a force is applied to the outside of the knee, causing the MCL to overstretch and possibly tear. This is common in contact activity such as football and soccer. The injury can also occur during the landing of a jump.

Common signs of an MCL injury include the following:

• pain and swelling in the knee joint, specifically the inner knee
• stiffness in the knee joint
• instability or buckling of the knee during activity or walking
• possible reported “catching” or “locking” of the knee

If you think your child may have an MCL tear, it is important to make an appointment with a Sports Medicine doctor.

The meniscus is a piece of cartilage that provides a cushion between your femur (thighbone) and tibia (shinbone). Meniscus injuries are one of the most common knee injuries. Activities that cause you to twist or rotate your knee, while putting your full weight on your knee, can lead to a torn meniscus.

Common signs and symptoms of a meniscus injury include the following:

• a popping sensation
• swelling or stiffness in the knee
• pain, especially when twisting or rotating your knee
• difficulty straightening your knee fully
• feeling as though your knee is locked in place when you try to move it

If you think your child may have a meniscus injury, you should schedule an appointment with a Sports Medicine doctor.

The patellar tendon is a thin band of tissue that connects the patella (kneecap) to the tibia (shin bone). Osgood-Schlatter Disease is an inflammation of this tendon where it inserts into the shin bone below the knee. Pain is caused by repeated stress from the tendon pulling on the bone during activity.

You may have Osgood-Schlatter Disease if you have the following:

• pain over your kneecap
• pain that increases with kneeling, jumping, or squatting
• a visible bump or swelling near the kneecap
• difficulty bending your knee

A trip to your doctor is necessary to treat Osgood-Schlatter Disease.

 Osteochondritis dissecans, is a condition that develops in joints, most commonly in children and adolescents. This condition occurs when a segment of bone underneath cartilage begins to die due to a lack of blood flow. This piece of bone and any cartilage attached can then crack and loosen, or completely detach.

The main cause of osteochondritis dissecans is thought to be repetitive trauma or stress to the bone and cartilage over time. Osteochondritis dissecans can also be caused by another injury, such as a meniscus tear in the knee, or ligamentous weakness.

Call your child’s doctor for any unexplained joint swelling or pain, or swelling or pain after trauma that does not subside in a reasonable amount of time. Contact the doctor as well for any joint catching or locking, or if your child does not have full range of motion of an affected joint.

A patellar subluxation is a temporary, partial dislocation of the patella (knee cap) with spontaneous relocation. Conversely, a patellar dislocation is a complete displacement of the patella from its normal position without spontaneous relocation.

The patella can slip out of place during forced leg straightening, a hard blow to the knee, or a fall.

Call the doctor if your child experiences persistent pain despite several days of rest and basic treatment, a visible deformity along your child’s knee, or a sense of instability of their knee cap along with pain.

Patellofemoral dysfunction is pain in the front of your knee where your kneecap (patella) glides abnormally at the end of your thigh bone (femur).

Patellofemoral dysfunction is usually seen in teenagers and is more common in females.

You may have patellofemoral dysfunction if you have pain in the front or back of your knees.

Treatment for Runner’s Knee required physical therapy, and often a brace. Because of this, if you suspect your child has Runner’s Knee you should schedule an appointment with a doctor.

Learn more about runner's knee.

Shin splint is a term that refers to pain located on the inside edge of the shin bone, or tibia. Athletes may also experience pain in the front of the lower leg.

Pain is caused by inflammation of the muscles, tendons and/or bone tissue located in the lower leg due to repeated stress from activity. The pain may progress to the point where an athlete will have pain during all activity, even with walking.

If the injury is not treated appropriately, the injury may progress to a tibial stress fracture.

Call the doctor for shin splints if your child complains of increased pains during practice, after practice, or with daily activities, is unable to complete practice or daily activities without pain, or shows signs of swelling or discomfort in the anterior (front) lower leg.

A sprain is when one or more ligaments in a joint become torn or stretched beyond its normal limits.

A strain, more commonly called a pulled muscle, is an injury to muscle fibers or tendon due to excessive force and stretching.

Sprains and strains may be caused from falls, direct forces or blows, improper warm-up leading to over stretching tissues, and inadequate rest between sport practices and competitions.

You should call the doctor for a sprain or strain if your child has severe pain and cannot put any weight on the injured joint or move it, the injured area looks different compared to the uninjured side, or has numbness in any part of the injured area.

A tendon is a thick band of tissue that connects muscle to bone. Inflammation or irritation of this thick band of tissue is called tendonitis.

Tendonitis is caused by overuse or improper use of the muscle and tendon. This occurs from doing the same activity repeatedly without enough rest time in between competition or training. Tendonitis can also be caused if an athlete repeatedly uses bad form in an activity.

Tendonitis is treated with rest from the activity that hurts. Ice and anti-inflammatory medication can help alleviate pain and swelling while your child is resting. Formal physical therapy or home exercises may help correct improper form.

Call your child’s doctor if your child has increasing pain, swelling or redness that does not go away with rest.