Knee Pain in a Teenager: Probable Diagnosis and Management
The most probable diagnosis for knee pain in a teenager is patellofemoral pain syndrome (anterior knee pain), which affects approximately 25% of young people and is the most common cause of knee pain in this age group. 1, 2
Most Common Diagnoses in Adolescents
The differential diagnosis for teenage knee pain includes:
Patellofemoral pain syndrome is the leading diagnosis in physically active adolescents under 40 years, presenting with anterior knee pain that worsens during activities like squatting (91% sensitivity for diagnosis when pain occurs during squat testing). 1, 2
Osgood-Schlatter disease is the second most common condition, presenting as pain and swelling at the tibial tuberosity insertion of the patellar tendon, typically in active adolescents during growth spurts. 3, 2, 4
Osteochondritis dissecans (OCD) should be considered, particularly if imaging reveals subchondral bone abnormalities or loose bodies, as this condition specifically affects adolescents and young adults. 5, 2, 4
Sinding-Larsen-Johanssen syndrome, plica syndrome, and patellar tendonitis are additional overuse injuries to consider in the athletic teenager. 2, 4
Critical Clinical Assessment
Look for anterior knee pain during squatting (91% sensitive for patellofemoral pain), assess for tibial tuberosity tenderness (Osgood-Schlatter), and perform McMurray testing if meniscal injury is suspected (61% sensitivity, 84% specificity). 1
Imaging Approach
Initial plain radiographs are appropriate when OCD, loose bodies, or structural abnormalities are suspected, but routine imaging is not required for typical patellofemoral pain. 5, 1
MRI without contrast is indicated when radiographs show OCD or when symptoms persist despite conservative management, as MRI can detect cartilage abnormalities, stress fractures, and determine OCD fragment stability (though hyperintense rims are less specific for instability in children versus adults). 5
Axial radiographs with weight-bearing views should be obtained when patellofemoral dysfunction is suspected to assess patellar tilt or subluxation. 6
First-Line Management Strategy
Quadriceps strengthening exercises are the cornerstone of treatment and must be prescribed to all teenagers with knee pain related to patellofemoral dysfunction or overuse injuries. 6, 3
Exercise therapy should include sustained isometric quadriceps exercises, proximal hip girdle strengthening, aerobic conditioning, and range of motion/stretching exercises following the principle of "small amounts often" linked to daily activities. 6
Start exercises within the patient's capability and progressively build intensity over several months to promote adherence and prevent re-injury. 6
Education and self-management strategies should be the mainstay of treatment, as long-standing knee pain often leads to reduced physical activity levels and 50% of adolescents continue experiencing pain for years without proper management. 3, 7
Adjunctive Conservative Measures
Patellar taping (medial direction) provides statistically significant short-term pain relief and should be used for acute symptom management while building strength through exercise (Grade B recommendation). 6
Patellofemoral braces provide symptomatic relief for lateral patellar subluxation or maltracking by resisting lateral displacement, with most patients reporting significant subjective improvements using off-the-shelf braces. 6
Prefabricated foot orthoses may benefit select patients with patellofemoral pain who respond favorably to treatment direction tests. 6
Activity modification, ice, and anti-inflammatory medications are appropriate initial conservative measures for overuse injuries. 4
Pharmacologic Management
Acetaminophen up to 4,000 mg/day is the first-line oral analgesic for knee pain that doesn't respond adequately to non-pharmacological approaches. 6
Topical NSAIDs have clinical efficacy with a favorable safety profile and should be considered before oral NSAIDs. 6
Oral NSAIDs should only be used if unresponsive to acetaminophen. 6
When to Consider Advanced Imaging or Referral
MRI is warranted if OCD is suspected on radiographs, as it determines fragment stability and guides treatment decisions (surgical versus conservative). 5
CT without contrast may be indicated to evaluate OCD patients or confirm loose bodies when MRI is not definitive. 5
Surgical referral is appropriate for severe traumatic meniscal tears (bucket-handle tears with displaced tissue) or unstable OCD lesions, but not for degenerative changes or stable lesions. 1
Critical Prognostic Information
Adolescent knee pain, particularly patellofemoral pain, is NOT self-limiting in most cases—55.9% of teenagers with knee pain continue to have symptoms 2 years later, and those with patellofemoral pain have a 1.26 times higher risk of persistent pain compared to other knee pain types. 7
Adolescents with patellofemoral pain are significantly more likely to reduce or stop sports participation compared to those with other types of knee pain. 7
Early detection and aggressive conservative management are essential to prevent chronic pain and activity limitation. 7
Common Pitfalls to Avoid
Do not assume teenage knee pain is "growing pains" that will resolve spontaneously—the majority of cases persist without proper treatment. 7
Avoid lateral wedged insoles, as they lack evidence and may worsen symptoms in patellofemoral pain. 6
Do not rush to surgery for degenerative meniscal tears or stable OCD lesions—exercise therapy for 4-6 weeks is first-line treatment even in the presence of mechanical symptoms. 1
Do not overlook referred pain from low back, hip, or pelvic pathology when evaluating knee pain in adolescents. 2