Initial Management of Knee Pain
Begin with plain radiographs (anteroposterior, lateral, and tangential patellar views) as the mandatory first step for all patients presenting with knee pain, followed by structured clinical evaluation to identify urgent conditions and guide further management. 1, 2
Immediate Assessment Priorities
Identify emergent conditions first that require urgent referral, including: 3, 4
- Severe pain with swelling and inability to bear weight following acute trauma 3
- Signs of septic arthritis: fever, joint swelling, erythema, and severely limited range of motion 3, 4
- Limb- or life-threatening conditions such as osteomyelitis or malignancy 4
Structured Clinical Evaluation
Obtain specific historical details including: 3, 5
- Age (guides differential diagnosis—adolescents more likely to have apophysitis or patellofemoral pain; older adults more likely osteoarthritis) 2, 6
- Location and quality of pain (anterior vs posterior vs medial/lateral compartment) 3
- Onset and duration (acute traumatic vs chronic/insidious) 3
- Mechanical symptoms (locking, catching, giving way suggest meniscal or ligamentous pathology) 3
- Presence and timing of swelling (immediate hemarthrosis suggests ACL tear or fracture; delayed suggests meniscal injury) 3, 6
Physical examination must systematically evaluate: 3, 5
- Inspection for effusion, erythema, deformity, muscle atrophy 3
- Palpation for joint line tenderness, warmth, point tenderness over specific structures 3
- Range of motion and strength testing 3
- Provocative maneuvers specific to suspected pathology 3
- Hip and lumbar spine examination to exclude referred pain 7
Imaging Algorithm
Plain radiographs are mandatory as the first imaging study for all patients ≥5 years with chronic knee pain or acute trauma meeting Ottawa criteria. 1, 2 This is non-negotiable and must include three views: anteroposterior, lateral (25-30 degrees flexion), and tangential patellar. 1, 2
Reserve radiographic imaging for: 3
- Chronic knee pain (>6 weeks duration) 3
- Acute traumatic pain in patients meeting evidence-based criteria 3
Proceed to MRI without IV contrast only if: 1, 2
- Radiographs are normal or show only effusion, but symptoms persist after 4-6 weeks of conservative treatment 1
- Radiographs demonstrate osteochondritis dissecans, loose bodies, or history of cartilage/meniscal repair 1
- Radiographs show signs of prior osseous injury requiring further characterization 1
Ultrasound is appropriate for: 1, 7
- Confirming suspected effusion and guiding aspiration 1
- Detecting popliteal cysts, particularly when loose bodies might be within the cyst 7
- Evaluating superficial structures and synovial pathology 1
Initial Treatment Strategy
For patellofemoral pain (most common in adolescents and young women): 8, 6
- Initiate knee-targeted exercise therapy focusing on quadriceps and hip muscle strengthening 8
- Decide whether hip-and-knee targeted exercise therapy is required based on tolerance to loaded knee flexion 8
- Prescribe exercise relative to symptom severity and irritability 8
Education must underpin all interventions and should: 8
- Challenge inaccurate beliefs about pain equaling damage 8
- Build confidence and understanding of diagnosis 8
- Manage expectations regarding recovery timeframes 8
- Promote autonomy and reduce fear of movement 8
Consider adjunctive interventions based on assessment findings: 8
- Prefabricated foot orthoses for those responding favorably to treatment direction tests 8
- Taping when rehabilitation is hindered by elevated symptom severity 8
- Movement/running retraining when symptoms align with specific biomechanical findings 8
Age-Specific Diagnostic Considerations
In adolescents (≥5 years): 2, 6
- Osgood-Schlatter disease (tibial tubercle apophysitis) is common in teenage boys 2, 6
- Sinding-Larsen-Johansson syndrome (inferior pole patella apophysitis) 2
- Patellofemoral pain syndrome is more common in teenage girls and young women 6
- Osteochondritis dissecans may cause activity-related pain with mechanical symptoms 2
In elderly patients (>70 years): 1, 7
- Osteoarthritis is the most common cause of chronic knee pain 1
- Bilateral structural abnormalities can exist with unilateral symptoms, limiting diagnostic discrimination 7
- Bone marrow lesions on MRI correlate with pain in osteoarthritis 1
Critical Pitfalls to Avoid
Do not overlook referred pain from hip or lumbar spine pathology before attributing all symptoms to knee pathology. 7 Complete thorough examination of lumbar spine and hip before proceeding with knee-focused imaging. 7
Avoid premature MRI use—approximately 20% of patients with chronic knee pain undergo MRI without recent radiographs, which violates the evidence-based imaging algorithm. 7
Recognize that not all imaging findings are symptomatic, particularly meniscal tears in patients over 45 years. 7
Specialty Referral Indications
Refer to orthopedics when: 2