Knee pain is a frequent concern for parents, ranging from harmless aches to symptoms of a more serious underlying condition. The knee is a complex joint under intense stress during a child’s rapid growth and high physical activity. Considering the nature, location, and associated symptoms of the pain helps determine the likely cause. This article explores the most common reasons a child’s knee might hurt, but it is not a substitute for a professional medical evaluation.
Intermittent Aches and Growing Pains
The term “growing pains” describes a common, benign pattern of muscular aches experienced by children, typically between the ages of three and twelve. This pain usually presents as a throbbing or aching sensation in the muscles, often affecting the calves, thighs, or behind the knees. A defining characteristic is that they occur late in the day or at night, sometimes waking a child, but are completely absent by morning.
Contrary to the name, the sensation is not directly caused by bone growth and does not involve the joint itself. These aches are theorized to result from muscular strain and overuse accumulated during a day of intense physical activity, such as running and jumping. Parents can manage these intermittent aches with simple home measures, including gentle massage or applying a covered heating pad. Over-the-counter pain relievers, such as acetaminophen or ibuprofen, can also be administered to relieve nighttime discomfort.
Pain Related to Activity and Overuse
Pain related to activity arises from repeated physical stress, especially during a growth spurt when bones may lengthen faster than muscles and tendons. Osgood-Schlatter disease causes localized pain and swelling just below the kneecap, at the tibial tubercle (the bony bump on the shinbone). This condition is common in adolescents, particularly boys aged 10 to 15, who participate in sports involving frequent running, jumping, and forceful quadriceps contraction. The constant pulling of the patellar tendon on the vulnerable growth plate causes irritation and inflammation.
Another common overuse injury is Patellofemoral Pain Syndrome (PFPS), often called “runner’s knee,” which causes a dull, aching pain around or under the kneecap. This discomfort is aggravated by activities that load the joint, such as climbing stairs, squatting, or sitting for long periods with the knee bent. The pain develops gradually over weeks or months due to repetitive motion rather than a single event. Similar conditions, such as Patellar Tendonitis (Jumper’s Knee), involve inflammation of the tendon connecting the kneecap to the shinbone, often seen in athletes who perform repetitive jumping motions.
When Trauma is the Cause
When knee pain begins immediately following a specific event, such as a fall, collision, or awkward twist, it is classified as acute trauma. Common acute injuries include ligament sprains (like to the MCL or ACL) and muscle strains. A sprain involves damage to the ligaments that connect bones, while a strain refers to an injury to a muscle or tendon. Fractures, particularly of the kneecap or growth plate, are also possible after high-impact trauma.
For immediate care of a non-severe acute injury, the R.I.C.E. principles (Rest, Ice, Compression, and Elevation) can help reduce initial swelling and pain. However, immediate medical evaluation is necessary if the child reports hearing an audible “pop” at the time of injury, experiences significant swelling, or is completely unable to bear weight. These symptoms may signal a substantial injury, such as a severe ligament tear or a bone fracture, requiring professional assessment, often including X-rays.
Warning Signs Requiring Urgent Medical Attention
Certain signs associated with knee pain are considered “red flags” and require prompt medical evaluation. These signs can indicate serious, non-traumatic conditions like infection, inflammation, or referred pain from the hip. Localized symptoms of concern include severe pain accompanied by joint swelling, warmth, or redness, which could signal a joint infection such as septic arthritis. A child who refuses to walk or is unable to bear weight due to the pain also needs urgent attention.
Systemic symptoms, such as fever, rash, unexplained weight loss, or general malaise accompanying the knee pain, may point toward an infectious or inflammatory process. Inflammatory conditions like Juvenile Idiopathic Arthritis (JIA) may present with knee pain and morning stiffness lasting longer than an hour. Pain felt only in the knee can also be referred pain originating in the hip. This is true for conditions like Slipped Capital Femoral Epiphysis (SCFE) in overweight adolescents, or Legg-Calvé-Perthes disease in younger children, both of which require hip examination for diagnosis.