Patient presents with right knee pain consistent with a strain.  Onset occurred while playing recreational basketball three days ago, characterized by a twisting injury during a sudden change in direction.  Patient reports experiencing immediate pain localized to the medial aspect of the right knee, followed by swelling and stiffness.  Pain is exacerbated by weight-bearing and activity, and alleviated by rest and ice.  Patient denies any popping or locking sensations.  Physical examination reveals tenderness to palpation along the medial joint line, mild effusion, and pain with valgus stress testing.  Range of motion is slightly limited due to pain and swelling.  No instability is noted.  McMurray test is negative.  Diagnosis of right knee strain is made, likely involving the medial collateral ligament.  Radiographs were obtained and are negative for fracture or dislocation.  Treatment plan includes RICE therapy (rest, ice, compression, elevation), NSAIDs for pain and inflammation, and physical therapy referral for range of motion exercises and strengthening.  Patient advised to avoid strenuous activity and weight-bearing as tolerated.  Follow-up scheduled in one week to assess progress and discuss further management, including potential for bracing if symptoms persist.  Differential diagnosis includes meniscus tear and ligament sprain, although current findings are more consistent with a mild to moderate strain.  ICD-10 code S86.111A, right knee strain, is assigned.  Patient education provided regarding activity modification, pain management strategies, and expected recovery timeline.