Knee pain is common in teenagers, often affecting their daily activities and sports. It can range from a dull ache to sharp discomfort. While many cases are not serious, understanding the potential causes is important for proper management. This pain frequently arises from physical changes during adolescence, including rapid growth and increased activity.
Growing Pains and Bone Development Issues
Rapid growth spurts during adolescence can contribute to specific knee conditions. Bones, muscles, and tendons sometimes grow at different rates, leading to tension at attachment points. This imbalance can result in inflammation where tendons connect to growth plates. Growth plates are less strong than fully formed bone, making them vulnerable to injury during accelerated growth.
Osgood-Schlatter disease is a common condition affecting approximately 1 in 10 adolescents aged 12 to 15 years. It involves pain, redness, and swelling at the tibial tuberosity, a bony bump below the kneecap where the patellar tendon attaches. Repetitive activities like running and jumping can cause the patellar tendon to repeatedly pull on this growth plate, leading to irritation and a painful bump.
Similarly, Sinding-Larsen-Johansson syndrome (SLJS) causes pain at the bottom of the kneecap. This condition results from irritation and swelling of the growth plate at the inferior pole of the patella, where the patellar tendon originates. SLJS often affects active teenagers, typically between 10 and 14 years old, who engage in sports involving frequent running, jumping, and kicking. Both Osgood-Schlatter disease and SLJS are self-limiting, resolving as the teenager matures and growth plates close.
Repetitive Stress Injuries
Knee pain in teenagers often stems from repetitive stress. Overuse, repeated motions, or suboptimal body mechanics can irritate knee structures. This type of injury is common in sports and physical activities involving frequent bending, straightening, jumping, or running. Continuous strain can lead to inflammation and discomfort in the knee joint.
Patellofemoral Pain Syndrome (PFP), sometimes called “runner’s knee” or “jumper’s knee,” is a common cause of pain around and behind the kneecap. This condition arises from repeated stress on the kneecap as it moves over the thigh bone. Factors like muscle imbalances, tight thigh muscles, or leg alignment issues can cause the kneecap to not glide smoothly. Symptoms include a dull ache that worsens with activities like climbing stairs, squatting, or prolonged sitting with bent knees.
Tendinitis, specifically patellar tendinitis (also known as “jumper’s knee”), is another repetitive stress injury. It affects the patellar tendon, which connects the kneecap to the shinbone. This condition develops from overuse and repeated stress, especially from jumping activities, causing tiny tears and inflammation within the tendon. Athletes in sports like volleyball and basketball are susceptible. Pain is typically felt directly below the kneecap and may be sharp during activity, lingering as a dull ache afterward.
Sudden Impact and Traumatic Injuries
Acute knee pain can result from falls, direct blows, or abrupt twisting motions. These traumatic events can damage various structures within the knee joint. Unlike chronic conditions, these injuries typically have an immediate onset of pain. Swelling and instability are often present, indicating potential structural damage.
Ligament sprains are frequent traumatic knee injuries. The anterior cruciate ligament (ACL) can tear when the knee twists or changes direction suddenly, often during sports. An ACL injury typically causes immediate pain, a “pop” sensation, and significant swelling, leading to instability. The medial collateral ligament (MCL), located on the inner side of the knee, is frequently injured by a direct blow to the outside of the knee or a forceful twisting motion. MCL injuries commonly present with pain and tenderness along the inside of the knee and sometimes swelling.
Meniscal tears involve damage to the C-shaped cartilage pads within the knee that act as shock absorbers. These tears commonly occur with a twisting injury, such as landing from a jump or making a sudden change in direction. Symptoms include pain, swelling, stiffness, and sometimes a clicking, popping, or locking sensation. Fractures, including growth plate fractures or patellar fractures, can also result from direct trauma or significant force. Growth plate fractures are specific to growing teenagers, as these areas are more susceptible to injury than mature bone.
When to Consult a Doctor
While many causes of knee pain in teenagers are not serious and resolve with rest, certain signs suggest a medical evaluation. Persistent pain that does not improve with rest, or pain that significantly interferes with daily activities, warrants attention. Severe swelling, especially if it occurs immediately after an injury, is a concerning symptom. The inability to bear weight on the affected leg or a noticeable limp also indicates a need for professional assessment.
Other red flags include any sensation of the knee locking, catching, or giving way, which can suggest mechanical issues. Pain accompanied by fever or chills, or pain that worsens at night and is not related to activity, should also prompt a doctor’s visit. Though rare, some serious conditions, such as infections or bone tumors, can present with knee pain. A medical evaluation helps ensure an accurate diagnosis and appropriate management plan.