Differential Diagnosis for Knee Pain in a 32-year-old Female

Single most likely diagnosis

• Overuse or repetitive strain injury: Given the patient's recent increase in lifting her children and the absence of any acute injury, overuse of the collateral ligaments or surrounding structures is a plausible cause for her knee pain. The pain being on the sides of the knee supports this, as it could indicate strain on the medial or lateral collateral ligaments.

Other Likely diagnoses

• Iliotibial (IT) band syndrome: This condition is common in individuals who have recently increased their physical activity, especially if it involves running, cycling, or repetitive knee bending. The IT band runs down the outside of the thigh from the hip to the knee, and friction or irritation of this band can cause pain on the sides of the knee.
• Patellofemoral pain syndrome: Although the pain is described as being on the sides of the knee, patellofemoral pain syndrome (PFPS) can sometimes present with pain in various areas around the knee, including the sides, due to maltracking of the patella or overuse.
• Bursitis: Prepatellar or pes anserine bursitis could cause knee pain, especially if the patient has been kneeling or putting pressure on her knees while lifting children. However, the absence of swelling makes this less likely.

Do Not Miss (ddxs that may not be likely, but would be deadly if missed)

• Osteonecrosis: Although less common, osteonecrosis (avascular necrosis) of the knee can present with pain, especially if the patient has a history of steroid use or other risk factors. It's crucial to consider this diagnosis to prevent progression and potential collapse of the bone.
• Infection or septic arthritis: Despite the absence of fever or swelling, it's essential to consider infectious causes, especially if the patient has a history of recent travel, immune compromise, or other risk factors.
• Tumor: Bone or soft tissue tumors around the knee can cause pain. While rare, missing a diagnosis of a tumor could have significant consequences.

Rare diagnoses

• Osgood-Schlatter disease: Typically seen in adolescents, this condition involves inflammation of the patellar tendon at its insertion on the tibia. It's less likely in a 32-year-old but could be considered if the patient has a history of unresolved adolescent knee issues.
• Plica syndrome: This involves irritation of the synovial folds within the knee joint, which can cause pain and snapping sensations. It's a less common cause of knee pain and might be considered if other diagnoses are ruled out.