The World Health Organization defines adolescence as ages 10-17 years old, while other sources say 13-20 years old. Knee pain from different causes can occur in this age range. Studies have determined that participation in sports and female gender are risk factors for adolescent knee pain.
What structures make up the knee joint?
The knee joint is comprised of bones, cartilage, synovial fluid, tendons, and ligaments. The bones consist of the lower femur (thigh bone), patella (knee cap), and upper tibia (shin bone). The cartilage and synovial fluid make up the “slippery substance” that allows the knee to glide and bend.
What types of conditions cause knee pain in adolescents?
Patellofemoral pain syndrome
Patellofemoral pain syndrome (PFPS) encompasses several conditions that cause pain in the front of the knee – at or around the patellar area.
In normal movement, the patella moves up, down, and sideways in a specific "groove." Anything that disturbs this normal movement can lead to pain, such as trauma from either a direct blow or cumulative trauma.
Adolescents with PFPS are usually athletes who participate in sports that involve running, jumping, climbing, squatting, or kneeling. Because of these types of injuries, PFPS is frequently called “runner’s knee” or “jumper's knee.”
PFPS also occurs in adolescents with structural abnormalities in other areas, including abnormal hip movement and posture; tightness in the thigh; or even flat feet (pes planus), which can cause an abnormal gait.
Osgood-Schlatter is a disease that involves a bump in front of the tibial bone (shin bone). It affects young people who are still growing, with boys more frequently affected than girls.
Young people have a growth plate made of cartilage that is present in the bones of their extremities. In the case of the knee, the patellar tendon reaches from the patella down toward the anterior (front) of the tibia and attaches to the tibial growth plate. Activities that strain the knee can cause the growth plate to swell, causing a prominence that leads to pain.
If you're curious about the name, it was named after two orthopedic surgeons who independently discovered the disease in 1903: Robert Bayley Osgood, an American, and Carl B. Schlatter from Switzerland.
The knee bursae are fluid-filled sacs that prevent friction between the skin, tendons, and bones. There are four main bursae of the knee:
- The suprapatellar bursa is above the knee.
- The infrapatellar bursa is below the knee.
- The prepatellar bursa is in front of the knee.
- The pes anserine bursa is on the inside of the knee joint.
When the bursa becomes inflamed, the amount of fluid in the sac increases and structural abnormalities can result. The inflamed bursa can be from numerous causes, such as infection; trauma, as in a fall or direct blow to the knee; gout; a difference in leg length leading to awkward walking; or repetitive issues with the knee like kneeling, squatting, or jumping.
Patellar tendonitis occurs when there is inflammation of the patellar tendon, the narrow piece that originates in the patella and ends on the tibia. This is the tendon that is tapped by a physician, with a reflex hammer, when checking the knee reflexes.
Patellar tendonitis is also called “jumper’s knee” since it commonly affects athletes who jump, like basketball or volleyball players. The repeated jumping over time places wear and tear on the tendon, thus forming tendonitis.
Knee injuries from trauma
These injuries can occur from a strain, sprain, or blunt force trauma that can cause damage to the meniscus (cartilage) or a ligament on the inside of the knee joint, resulting in tears or injuries of different structures:
- The medial (inside) meniscus or lateral (outside) meniscus
- The anterior cruciate ligament (ACL)
- The posterior cruciate ligament (PCL)
Juvenile idiopathic arthritis
Juvenile idiopathic arthritis (JIA) is an arthritic condition affecting children 16 years of age and younger, that used to be called juvenile rheumatoid arthritis. It is of unknown cause, hence the word “idiopathic.”
What are the physical exam findings for the different types of adolescent knee pain?
A physician or medical provider should thoroughly examine the knee area, since different adolescent knee disorders have different exam findings.
With patellofemoral pain syndrome (PFPS), there is tenderness at or around the patella, while Osgood-Schlatter disorder reveals a prominence just below the patellar tendon.
With prepatellar bursitis, there is tenderness at the patellar (kneecap) area, while pes anserine bursitis exhibits tenderness inside the knee, about 2 inches below the kneecap. In bursitis, not only is the area swollen and tender, but it can be warm and red.
Patellar tendonitis, as the name implies, demonstrates tenderness with occasional swelling at the patellar tendon.
What laboratory tests need to be done in an adolescent with knee pain?
Laboratory tests can help with the diagnosis, especially if more serious conditions, like cancers, are suspected and must be ruled out. A complete blood count (CBC) can show increased white blood cells (WBC), indicating inflammation. Anemia can be present with some chronic diseases.
An erythrocyte sedimentation rate (ESR) is a general inflammatory marker and assists with diagnosis. In addition, a rheumatoid factor (RF) can be positive in adolescents with JIA.
What diagnostic imaging studies should be done?
Plain X-rays of the knees should be done on any adolescent with knee pain since these are needed to rule out any underlying bone abnormalities, such as a fracture or dislocation of the femur, tibia, fibular, and patella.
A computed tomography (CT or CAT) scan can be done to evaluate soft tissues, such as muscles, tendons, cartilage, or ligaments; however, magnetic resonance imaging (MRI) is the “gold standard” for evaluations of soft tissues and bone. Both CT scans and MRIs use computers to provide three-dimensional viewing, allowing medical viewers to see intricate details of the knee and joint space.
What medicines can be used to treat adolescent knee pain?
There are over-the-counter (OTC) pain medicines like acetaminophen (Tylenol) for knee pain, but use caution since excessive Tylenol use can lead to liver disease.
For pain and inflammation, nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin (Bayer, Ecotrin, Anacin), ibuprofen (Advil, Motrin), or naproxen (Aleve), can also be used, along with a higher dose for anti-inflammatory purposes. However, caution must be used with all NSAIDs, as there is a risk of gastrointestinal (GI) irritation, causing stomach ulcers and bleeding.
Besides medicines, what else can I do to treat knee pain in adolescence?
Physical therapy (PT) and occupational therapy (OT) can help with modality treatments, such as electrical stimulation and ultrasound, directions for specific exercises, and postural recommendations.
Hot and cold therapy can be very effective. The old-fashioned idea was to use ice for the acute injury (first 24 hours) and then use heat. However, everyone is different; some adolescents will respond better to ice, and some will respond better to heat.
Steroid injections can help with inflammation and pain, depending on the situation. The injection can be given intramuscular or directly into the knee joint.