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?

In order to determine the underlying causes of the knee pain experienced by the 15-year-old male, additional history must be obtained. The following information would be essential to gather:

1. Onset and duration of symptoms: Determining when the pain began and how long it has lasted can provide insight into the potential causes.
2. Location and radiation of pain: Identifying whether the pain is localized to a specific area or radiates to other parts of the knee or leg can help in narrowing down the differential diagnosis.
3. Severity and exacerbating factors: Understanding the level of pain and any factors that worsen or alleviate it can provide valuable clues.
4. Associated symptoms: Inquiring about any additional symptoms like swelling, redness, warmth, or locking of the knee joint can aid in the diagnostic process.
5. Trauma and previous injuries: Inquiring about any history of trauma or previous knee injuries can help determine if the pain is related to a specific incident or previous pathology.
6. Activity level and sports involvement: Understanding the patient’s level of physical activity and sports participation can give insights into potential overuse injuries or biomechanical factors contributing to the knee pain.

Knee pain can be differentiated into various categories, including acute, chronic, traumatic, mechanical, inflammatory, or infectious. Acute knee pain typically occurs suddenly and is often associated with a specific event or injury. Chronic knee pain, on the other hand, lasts for a prolonged period, usually more than three months. Traumatic knee pain is related to a direct impact or injury, whereas mechanical knee pain is usually a result of overuse or abnormal joint mechanics. Inflammatory knee pain is associated with conditions such as arthritis, while infectious knee pain can be caused by an infection in the joint.

Based on the provided information, several potential differential diagnoses for knee pain in this patient can be considered. These include:

1. Patellofemoral pain syndrome: Often associated with activities like running or jumping, this condition involves pain and clicking sensations beneath the patella (kneecap).
2. Osgood-Schlatter disease: Common in active adolescents, it causes pain below the patella due to inflammation and small fractures at the site of tendon insertion.
3. Meniscal tear: A common knee injury, usually caused by twisting or direct trauma, resulting in pain, clicking, and a catching sensation.
4. Osteochondritis dissecans: A condition where a piece of cartilage and underlying bone detaches, causing knee pain, clicking, and locking.
5. Patellar subluxation or dislocation: The patella temporarily moves out of position, causing pain, clicking, and catching sensations.
6. Osteoarthritis: Although less common in young individuals, it could be considered if other causes are ruled out. It typically presents as chronic pain, stiffness, and limited mobility.

During the physical examination, a systematic approach should be followed. The following anatomic structures should be assessed:

1. Inspection: Look for signs of swelling, redness, deformity, or asymmetry.
2. Palpation: Assess for tenderness, warmth, and any abnormalities over the knee joint, including the patella, ligaments, and tendons.
3. Range of motion: Evaluate the patient’s ability to flex and extend the knee and any limitations, pain, or crepitus during movement.
4. Muscle strength and stability: Test the strength of the quadriceps and hamstring muscles, as well as the stability of the knee joint.
5. Special tests: Perform specific maneuvers such as the Lachman test, McMurray’s test, or patellar apprehension test to assess ligament stability, meniscal integrity, and patellar tracking, respectively.

In conclusion, to determine the causes of knee pain in a 15-year-old male, a detailed history, including onset, location, severity, associated symptoms, trauma, and activity level, should be obtained. Differential diagnoses for knee pain in this patient may include patellofemoral pain syndrome, Osgood-Schlatter disease, meniscal tear, osteochondritis dissecans, patellar subluxation/dislocation, or osteoarthritis. The physical examination should involve a thorough assessment of the knee joint, including inspection, palpation, range of motion, muscle strength, stability testing, and specific maneuvers.