What is the recommended assessment and treatment for knee pain?

Assessment and Treatment of Knee Pain

Begin with plain radiographs (AP, lateral, tangential patellar, and tunnel views) as the initial imaging study for all patients ≥5 years old presenting with chronic knee pain. 1

Initial Clinical Assessment

History - Key Elements to Elicit

• Pain characteristics: Location (anterior, medial, lateral, diffuse), duration (acute vs chronic >3 months), quality, and aggravating factors 2, 3
• Mechanical symptoms: Locking (motion halted), catching (motion partially inhibited), popping, or giving way 1
• Activity-related patterns: Pain with squatting suggests patellofemoral pathology (91% sensitive, 50% specific), while activity-related pain with <30 minutes morning stiffness in patients ≥45 years suggests osteoarthritis (95% sensitive, 69% specific) 4
• Previous treatments and their effectiveness 5
• Impact on daily activities and quality of life 5

Physical Examination - Specific Findings

• Inspection: Effusion, localized swelling, patella height abnormalities (alta or baja), gait abnormalities 1
• Palpation: Joint line tenderness (83% sensitive and specific for meniscal tears), crepitus 1, 4
• Range of motion: Loss of motion, pain with specific movements 1
• Strength testing: Quadriceps and hamstring strength, with particular attention to vastus medialis weakness and imbalance with vastus lateralis 5, 6
• Special tests: McMurray test for meniscal tears (61% sensitive, 84% specific - perform with concurrent knee rotation and extension) 4

Consider Referred Pain Sources

• Hip pathology: Obtain hip radiographs if knee radiographs are unremarkable and clinical concern exists for hip disease 1
• Lumbar spine pathology: Consider lumbar spine imaging if knee radiographs are unremarkable and lower back pathology is suspected 1

Imaging Algorithm

Step 1: Initial Radiographs (Always First)

Obtain knee radiographs including AP, lateral, tangential patellar (sunrise/Merchant), and tunnel views for all patients with chronic knee pain. 1

Critical pitfall: Approximately 20% of patients with chronic knee pain undergo MRI without recent (within prior year) radiographs - this is premature and unnecessary. 1

Step 2: Further Imaging Based on Radiographic Findings

If Radiographs are Normal or Show Only Joint Effusion:

• Proceed to MRI knee without IV contrast when pain persists despite normal or minimally abnormal radiographs 1
• MRI detects effusion extent, synovitis, popliteal cysts, subchondral cysts, articular cartilage abnormalities, meniscal tears, and bone marrow lesions 1

Important caveat: Meniscal tears are often incidental - the majority of people >70 years have asymptomatic meniscal tears, and prevalence is similar in painful vs asymptomatic knees in patients 45-55 years old 1

If Radiographs Show Osteochondritis Dissecans, Loose Bodies, or History of Cartilage/Meniscal Repair:

• MRI knee without IV contrast is indicated 1

If Radiographs Show Osteoarthritis or Chondrocalcinosis:

• Three options may be appropriate depending on clinical scenario: 1
  • MRI knee without IV contrast (most common)
  • Knee aspiration (if infection or crystal disease suspected)
  • CT knee without IV contrast (specific instances)

If Radiographs Show Prior Chronic Injury (Segond fracture, tibial spine avulsion):

• MRI knee without IV contrast to evaluate medial patellofemoral ligament, cartilage injury, menisci, and loose bodies 1

Special Circumstances:

• CT without IV contrast: For patellofemoral subluxation/maltracking evaluation, trochlear morphology, tibial tubercle-trochlear groove distance 1
• CT arthrography: Alternative to MRI for menisci and articular cartilage evaluation (86-100% sensitivity and specificity) 1

Treatment Algorithm by Diagnosis

Osteoarthritis (Most Common in Patients ≥45 Years)

First-Line Non-Pharmacological Treatment (Start Here):

• Exercise therapy: Regular strengthening exercises (especially quadriceps), low-impact aerobic activity 30-60 minutes most days (effect size 0.52 for pain, 0.46 for disability) 1, 7, 4
• Weight reduction: Minimum 5% body weight loss if BMI ≥25 kg/m², combining dietary modification with exercise 7
• Education and self-management programs: Individualized education, coping skills training, activity modifications 1, 7
• Appliances: Walking sticks, insoles (but NOT lateral wedge insoles), knee bracing 1, 7

Pharmacological Treatment Progression:

1. Acetaminophen (paracetamol) first: Initial oral analgesic for mild-moderate pain 1, 7
2. NSAIDs if acetaminophen fails: Non-selective NSAIDs with gastroprotective agents OR selective COX-2 inhibitors for patients with increased GI risk 1, 7
3. Topical NSAIDs and capsaicin: Clinically effective and safe 7
4. Tramadol: For moderate-severe pain 7

Intra-Articular Injections:

• Corticosteroid injections: Indicated for acute exacerbations, especially with effusion 1, 7, 8
  • Dose: 5-15 mg triamcinolone acetonide for larger joints like the knee, up to 40 mg for larger areas 8
  • Strict aseptic technique mandatory; inject deeply into joint space 8
• Hyaluronic acid: May have symptomatic effects but evidence is mixed (AAOS does not recommend, but EULAR suggests possible benefit) 7

Surgical Referral:

Consider joint replacement for patients with radiographic evidence of end-stage OA (minimal/no joint space) and refractory pain/disability despite exhausting all appropriate conservative options. 7, 4

Patellofemoral Pain (Most Common in Patients <40 Years, Physically Active)

Treatment Protocol (3-Month Minimum Before Considering Other Options):

Phase 1 - Pain Control and Muscle Balance (First 2-4 Weeks):

• Reduce pain and swelling 6
• Correct vastus medialis-vastus lateralis imbalance BEFORE starting quadriceps exercises 6
• Restore normal gait 6
• Decrease patellofemoral joint loading 6

Phase 2 - Strength and Coordination (Weeks 4-8):

• Hip and knee strengthening exercises combined with foot orthoses or patellar taping 4, 9
• Improve postural control and lower extremity coordination 6
• Increase quadriceps and hip muscle strength 6, 9

Phase 3 - Functional Return (Weeks 8-12):

• Functional exercises and return to regular physical activity 6
• Single-leg functional tests and functional knee scores for outcome evaluation 6

Key principles: Education to improve patient understanding, pain management strategies, load control and progression with emphasis on exercise therapy 9

No indication for surgery in patellofemoral pain. 4

Meniscal Tears

Conservative Management First (4-6 Weeks):

Exercise therapy is first-line treatment for both traumatic and degenerative meniscal tears, even in the presence of mechanical symptoms (locking, catching). 4

Surgical Indications:

• Severe traumatic bucket-handle tears with displaced meniscal tissue - surgery likely required 4
• Degenerative meniscal tears: Surgery is NOT indicated even with mechanical symptoms 4

Key Clinical Pitfalls to Avoid

1. Do not order MRI without recent radiographs - this occurs in 20% of cases and is inappropriate 1
2. Do not over-interpret meniscal tears on MRI in older patients - most are asymptomatic incidental findings 1
3. Do not rush to surgery for degenerative meniscal tears - exercise therapy is superior 4
4. Do not start quadriceps strengthening before correcting vastus medialis-lateralis imbalance in patellofemoral pain 6
5. Do not use lateral wedge insoles - not recommended 7