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Knee Pain in Adults and Adolescents: The Initial Evaluation

Bernadette Pendergraph, MD
John Cheng, MD
Stephanie Diana Garcia, MD

American Family Physician. 2026;114(1):49-62.

Author disclosure: No relevant financial relationships.

This clinical content conforms to AAFP criteria for CME.

Knee pain is common, with more than 30% to 45% of middle-aged and older adults having symptomatic osteoarthritis, and 25% to 40% of younger adults having patellofemoral pain syndrome. Components of a detailed history include time of onset; pain duration, quality, and localization; trauma/mechanism of injury; swelling; popping/clicking; aggravating and alleviating factors; sports activities; and limitations to current activity. The physical examination for evaluating knee pain involves five overall components: inspecting the joint for obvious abnormalities, palpating the joint to identify effusion or points of tenderness that may be the source of the pain; testing active and passive range of motion; testing strength; and performing specialized maneuvers that evaluate specific knee joint structures. These maneuvers are most accurate when performed in combination, rather than relying on one specific maneuver to make the diagnosis. In addition to these five examination components, imaging should be obtained if appropriate, with plain radiography typically being the first step. With traumatic injuries, clinical decision rules such as the Ottawa Knee Rule can determine if radiography is needed to detect fractures or other injuries that may require referral. Additional evaluations can include arthrocentesis when joint effusion is present, optimally guided by point-of-care ultrasonography when available, and laboratory testing if infection or inflammatory disorders are suspected.

The prevalence of knee pain is increasing as the population ages. The increase is also associated with the rising incidence of obesity. More than 30% of individuals older than 45 years have symptomatic knee osteoarthritis, increasing to 45% by age 85 years. Patellofemoral pain syndrome is the most common cause of knee pain in people younger than 45 years, accounting for 25% to 40% of cases.1,2 Acute knee injuries are also common in young adults, including nonspecific sprains and structural injuries (Table 13).

WHAT'S NEW ON THIS TOPIC

Knee Pain
More than 30% of individuals older than 45 years have symptomatic knee osteoarthritis, increasing to 45% by age 85 years. Patellofemoral pain syndrome is the most common cause of knee pain in people younger than 45 years, accounting for 25%–40% of cases.
POCUS is increasingly available in office settings, but its diagnostic accuracy depends on operator experience. Using POCUS to guide knee arthrocentesis increases success rate, increases volume aspirated, and decreases pain.

POCUS = point-of-care ultrasonography.

TABLE 1. Frequency of Acute Knee Injuries in Young Adults

Knee injury % of all knee injuries
Nonspecific sprain/strain 33.9
Anterior cruciate ligament injury 20.3
Medial meniscal lesion 10.8
Cartilage lesion 10.6
Medial collateral ligament injury 7.9
Contusion 5.5
Lateral meniscal lesion 3.7
Patellar dislocation 3.3
Lateral collateral ligament injury 1.1
Fracture 1
Posterior cruciate ligament injury 0.7
Tendon injury 0.2
Other 1

Information from reference 3.

BERNADETTE PENDERGRAPH, MD, is an associate professor in the Department of Family Medicine at the David Geffen School of Medicine, University of California, Los Angeles (UCLA), Harbor City, and associate program director at the Harbor-UCLA Family Medicine Residency Program, Harbor City.

JOHN CHENG, MD, is an associate professor in the Department of Family Medicine at the David Geffen School of Medicine, UCLA, Harbor City, and faculty at the Harbor-UCLA Family Medicine Residency Program, Harbor City.

STEPHANIE DIANA GARCIA, MD, is faculty at the Harbor-UCLA Family Medicine Residency Program, Harbor City.

Address correspondence to Bernadette Pendergraph, MD, at bpendergraph@dhs.lacounty.gov.

Author disclosure: No relevant financial relationships.

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