A 15-year-old male reports dull pain in both knees. Sometimes one or both knees click, and the patient describes a catching sensation under the patella. In determining the causes of the knee pain, what additional history do you need? What categories can you use to differentiate knee pain? What are your specific differential diagnoses for knee pain? What physical examination will you perform? What anatomic structures are you assessing as part of the physical examination? What special maneuvers will you perform?

Introduction
Knee pain is a common complaint among individuals of all ages, including adolescents. When evaluating a 15-year-old male with knee pain, additional history, as well as a physical examination, is necessary to determine the cause of the pain. This paper will discuss the additional history needed, categories to differentiate knee pain, specific differential diagnoses for knee pain, the physical examination to be performed, anatomic structures assessed during the examination, and special maneuvers that may be used.

Additional History
In order to fully evaluate the cause of knee pain in a 15-year-old male, obtaining a thorough history is essential. The history should include the following information:

1. Onset and Duration: Inquire about the duration of the knee pain and whether it occurred suddenly or gradually.
2. Trauma: Determine if there was any recent trauma to the knee, such as a fall, sports injury, or direct impact.
3. Activity Level: Assess the patient’s activity level, including participation in sports, exercise routines, and any recent changes in activity.
4. Previous Episodes: Ask if the patient has experienced similar knee pain in the past and if so, the frequency and severity of these episodes.
5. Location: Determine the exact location of the knee pain, including whether it is localized to a specific area or if it radiates to other regions.
6. Associated Symptoms: Inquire about any additional symptoms, such as swelling, stiffness, weakness, locking, giving way, or clicking sounds in the knee.
7. Pain Characteristics: Assess the nature of the pain, including its intensity, quality, and any factors that exacerbate or alleviate it.
8. Medical History: Obtain the patient’s medical history, including any previous knee injuries, surgeries, or underlying medical conditions, such as arthritis or ligamentous laxity.

Differentiating Categories of Knee Pain
Knee pain can be categorized into various subtypes based on the underlying pathology. These categories include:

1. Traumatic: Knee pain resulting from a direct blow, fall, or sports injury.
2. Overuse: Pain caused by repetitive activities, excessive exercise, or training errors.
3. Inflammatory: Pain associated with underlying inflammatory conditions, such as rheumatoid arthritis or gout.
4. Mechanical: Pain caused by structural abnormalities or mechanical derangements, such as meniscal tears or patellofemoral syndrome.
5. Infection: Knee pain resulting from an infectious process, such as septic arthritis.
6. Neoplastic: Knee pain associated with tumors or malignancies.

Specific Differential Diagnoses for Knee Pain
Based on the additional history provided and the differentiation of knee pain categories, several specific differential diagnoses can be considered. These may include:

1. Patellofemoral Pain Syndrome: A common cause of anterior knee pain, typically associated with activities that place stress on the patellofemoral joint.
2. Osteochondritis Dissecans: A condition characterized by a disruption in the blood supply to the subchondral bone, leading to a fragment of the bone and cartilage detaching from the underlying bone.
3. Meniscal Tear: Injuries to the C-shaped cartilages within the knee joint that can cause pain, clicking, catching, and swelling.
4. Ligamentous Injuries: Including anterior cruciate ligament (ACL) tears, medial collateral ligament (MCL) sprains, or posterior cruciate ligament (PCL) tears.
5. Osgood-Schlatter Disease: A condition characterized by inflammation and irritation of the patellar tendon at the tibial tuberosity, commonly seen in adolescents involved in sports.
6. Juvenile Idiopathic Arthritis: A chronic inflammatory condition that affects the joints and can cause knee pain, swelling, and stiffness in adolescents.
7. Osteochondral Defect: A lesion or defect in the articular cartilage and underlying bone, commonly seen in the knee joint.

Physical Examination
The physical examination of the knee is crucial in identifying potential causes of the pain. The examination should include the following components:

1. Inspection: Observe the knee for any visible abnormalities, such as swelling, redness, deformities, or scars.
2. Palpation: Assess the knee joint and surrounding structures, including the patella, femoral condyles, tibial plateaus, collateral ligaments, and patellar tendon.
3. Range of Motion: Evaluate the patient’s ability to flex, extend, and rotate the knee joint.
4. Stability Testing: Assess the stability of the knee joint by performing various tests, such as the Lachman test, anterior and posterior drawer tests, and valgus and varus stress tests.
5. Neurovascular Examination: Evaluate the neurovascular status of the lower leg, including sensation, pulses, and motor function.

Anatomic Structures Assessed during the Examination
During the physical examination, several anatomic structures are assessed to determine the cause of knee pain. These include:

1. Bones: The femur, tibia, fibula, and patella are assessed for signs of fractures, defects, or deformities.
2. Ligaments: The ACL, MCL, LCL, and PCL are evaluated for stability.
3. Menisci: The medial and lateral menisci are assessed for signs of tears or other abnormalities.
4. Patella: The patella is examined for proper alignment and signs of maltracking or subluxation.
5. Muscles and Tendons: The quadriceps, hamstrings, and other surrounding muscles and tendons are examined for signs of weakness, atrophy, or tenderness.

Special Maneuvers
In addition to the standard physical examination, several special maneuvers may be performed to further evaluate the knee. These may include:

1. McMurray Test: A maneuver used to assess for meniscal tears by rotating the knee with simultaneous valgus or varus stress.
2. Thessaly Test: An alternative to the McMurray test, the Thessaly test involves the patient standing on one leg and rotating the body while keeping the knee flexed, which may elicit pain or a mechanical sensation.
3. Patellar Apprehension Test: A maneuver used to assess for patellar instability by attempting to laterally dislocate the patella.
4. Lachman Test: A test used to assess the stability of the ACL by applying an anterior force on the tibia while stabilizing the femur.

Conclusion
Evaluating a 15-year-old male with knee pain requires gathering additional history and performing a comprehensive physical examination. This process involves assessing various anatomic structures, using special maneuvers, and considering specific differential diagnoses based on different categories of knee pain. By thoroughly investigating the patient’s history and conducting a systematic examination, healthcare professionals can accurately diagnose and manage the underlying cause of the patient’s knee pain.