Knee Pain Assessment and Documentation in Patients with Prior Injuries
Begin with plain radiographs (anteroposterior, lateral, and tangential patellar views) as the mandatory first imaging step, followed by a structured clinical evaluation that specifically documents mechanism of prior injury, current mechanical symptoms, focal tenderness patterns, effusion characteristics, and functional limitations—then proceed to MRI without contrast only if radiographs show abnormalities requiring further characterization or if symptoms persist despite adequate conservative treatment. 1
Essential History Documentation
Document these specific elements to guide diagnosis and avoid missing critical pathology:
- Prior injury mechanism and timing: Specify whether previous injuries involved acute trauma, twisting mechanisms, or direct blows, as this predicts current pathology patterns 2, 3
- Current pain characteristics: Location (medial, lateral, anterior, posterior), quality, timing, and aggravating factors 4, 2
- Mechanical symptoms: Locking, popping, giving way, or catching sensations suggest meniscal tears or loose bodies 2, 3
- Effusion history: Document timing of swelling onset (immediate suggests hemarthrosis from fracture or ligament tear; delayed suggests meniscal injury), amount, and recurrence patterns 2
- Functional limitations: Inability to bear weight, difficulty with stairs, squatting, or kneeling 2, 5
- Constitutional symptoms: Fever, weight loss, or systemic symptoms that suggest infection or inflammatory arthropathy 6, 7
Critical Physical Examination Components
Always examine the uninjured knee first for comparison 3
Inspection and Palpation
- Focal tenderness mapping: Palpate joint line spaces, patellar margins, tibial tubercle, fibular head, and medial/lateral femoral condyles to localize pathology 2, 3
- Effusion assessment: Use ballottement or bulge sign to detect and quantify joint effusion 2
- Alignment and gait: Document varus/valgus deformity and antalgic gait patterns 2
Range of Motion and Stability Testing
- Active and passive ROM: Document flexion/extension limitations and compare to contralateral side 2, 3
- Ligament stability: Perform valgus/varus stress testing for collateral ligaments, Lachman and pivot shift for anterior cruciate ligament, posterior drawer for posterior cruciate ligament 3
- Meniscal evaluation: McMurray's test, Apley's grind test, and bounce test for meniscal pathology 3
Mandatory Referred Pain Assessment
This is a critical pitfall to avoid: Always examine the hip (range of motion, impingement testing) and lumbar spine (neurologic examination, straight leg raise) before attributing all symptoms to knee pathology 8, 6, 9
- Hip pathology commonly refers pain to the knee, particularly in patients with unremarkable knee radiographs 8, 9
- Lumbar spine pathology must be considered if knee imaging is normal but pain persists 8, 9
Imaging Algorithm
Initial Imaging: Plain Radiographs
Radiographs are mandatory as the first imaging study for all patients ≥5 years with chronic knee pain or acute trauma meeting Ottawa criteria 1
Required views:
When to Proceed to MRI Without Contrast
MRI is indicated in these specific scenarios 1:
- Radiographs normal or show only effusion, but symptoms persist after 4-6 weeks of conservative treatment 1, 6
- Radiographs demonstrate signs of prior osseous injury (Segond fracture, tibial spine avulsion) requiring soft tissue evaluation 1
- Radiographs show osteochondritis dissecans, loose bodies, or history of cartilage/meniscal repair 1
- Clinical concern for patellar dislocation-relocation (MRI assesses medial patellofemoral ligament integrity, cartilage injury, loose bodies) 1
Alternative Imaging Modalities
- CT without contrast: May be appropriate for patellofemoral anatomy evaluation in repetitive subluxation or to confirm prior osseous injury 1
- Ultrasound: Useful for confirming effusion, guiding aspiration, detecting synovial pathology, and evaluating popliteal cysts 1, 8, 9
- Joint aspiration: Indicated only if effusion present with concern for crystal disease or infection 1
Documentation Requirements
Specify Laterality
Always document right versus left knee using specific codes, never "unspecified" 9
Document Imaging Sequence
Approximately 20% of patients inappropriately receive MRI without recent radiographs (within past year)—this must be avoided 8, 9
Record Conservative Treatment Trial
Document the duration and types of conservative measures attempted (activity modification, physical therapy, NSAIDs, ice) before proceeding to advanced imaging 6, 7
Common Pitfalls to Avoid
- Premature MRI ordering: Do not skip radiographs; MRI should not be the first imaging study 8, 9
- Overlooking referred pain: Failure to examine hip and lumbar spine leads to missed diagnoses 8, 6, 9
- Over-interpreting incidental findings: Not all meniscal tears seen on MRI are symptomatic, particularly in patients >45 years 8
- Ignoring bilateral findings in elderly: In patients >70 years, bilateral structural abnormalities may be present with unilateral symptoms 8
- Missing red flags: Constitutional symptoms, neurologic deficits, inability to bear weight, or palpable masses require immediate specialist referral 1, 6
Age-Specific Considerations
Pediatric Patients (≥5 years)
- Consider Osgood-Schlatter disease, Sinding-Larsen-Johansson syndrome, patellofemoral pain syndrome 1, 6
- Most pediatric knee pain is self-limiting; start with clinical assessment without imaging unless red flags present 6