Knee pain - assessment
Exam Tips
- In trauma OSCEs, quote effusion timing: haemarthrosis within about 2 hours suggests ACL rupture/fracture/dislocation; delayed 24-36 hour swelling suggests meniscal injury or sprain.
- Use Ottawa Knee Rules to justify X-ray decisions in acute injury and mention inability to weight bear four steps as a key trigger.
- Do not over-interpret crepitus/clicking alone; they are common and poorly discriminatory.
- Prioritise red flags: hot swollen immobile joint with fever, inability to straight-leg raise, neurovascular deficit, severe night/rest pain, and unexplained weight loss.
- Always examine above and below the knee (hip, ankle, spine), especially in children where referred hip pathology may present as knee pain.
- If discussing anatomy in viva, reference a standard ligament map diagram (ACL/PCL/MCL/LCL and extensor mechanism) for mechanism-based localisation.
Definition
Knee pain assessment is the structured clinical evaluation of pain arising from the knee joint or referred from nearby or systemic pathology. In UK practice it focuses on identifying the pain generator, excluding time-critical causes such as fracture, tendon rupture, dislocation, septic arthritis, or malignancy, and directing appropriate conservative, medical, or urgent orthopaedic/rheumatology pathways.
Pathophysiology
Knee pain is a symptom with multiple mechanisms: nociceptive pain from synovium, periosteum, ligaments, menisci, tendon, bursa, and subchondral bone; inflammatory pain from crystal or autoimmune synovitis; and less commonly neuropathic/referred pain from lumbar radiculopathy or hip disease. Traumatic haemarthrosis typically develops rapidly (often within 2 hours) in major intra-articular injury (for example ACL rupture, patellar dislocation, fracture), whereas slower effusion over 24-36 hours is more typical of meniscal injury or lower-grade ligament sprain. Chronic overload (patellofemoral pain, tendinopathy), degenerative cartilage/subchondral change (osteoarthritis), and biomechanical factors (maltracking, obesity, occupational kneeling/squatting) perpetuate symptoms and disability.
Risk Factors
- Increasing age (especially osteoarthritis risk >45 years)
- Overweight or obesity
- Previous knee injury or surgery
- Knee-straining occupation (kneeling, squatting, heavy lifting, cramped workspaces)
- High-impact/torsional sport participation
- High overall physical activity load without adequate recovery
- Mental distress or depression
- Social deprivation
- South Asian ethnicity
Clinical Features
Symptoms
- Pain characteristics: site (anterior/medial/lateral/posterior), severity, quality, radiation, intermittent vs constant
- Temporal pattern: immediate post-trauma pain vs delayed onset
- Aggravating/relieving factors (stairs, twisting, squatting, weight-bearing, rest/night pain)
- Swelling history and timing (rapid tense swelling suggests significant intra-articular injury)
- Mechanical symptoms: true locking, giving way, instability, loud pop at injury
- Stiffness pattern (including morning stiffness suggesting inflammatory disease)
- Systemic symptoms: fever, malaise, rash, weight loss/night sweats
- Functional impact: walking distance, stairs, sport/work limitation
- Associated history: psoriasis, IBD, uveitis, gout/pseudogout, recent diarrhoeal/GU infection, immunosuppression
Signs
- Inspection: deformity, erythema, effusion, muscle wasting, wounds, patellar position abnormalities
- Palpation: warmth, joint-line tenderness, bursal tenderness/swelling, bony tenderness
- Range of movement (normal approximately 0 degrees extension to 135 degrees flexion), painful arc or block
- Gait and ability to weight bear
- Features of septic arthritis: hot swollen joint with markedly restricted movement and systemic upset
- Trauma-focused findings: extensor lag/failed straight-leg raise, palpable tendon gap, patella alta/baja
- Ligament laxity on valgus/varus stress, Lachman/anterior drawer/posterior drawer
- Neurovascular status: distal pulses, capillary refill, sensation, motor function; assess for compartment syndrome when relevant
- Examination of hip, ankle, and lumbosacral spine for referred pain (especially in children/adolescents)
Investigations
Management
Lifestyle Modifications
- Safety-net and urgent same-day referral for red flags (suspected septic arthritis, fracture, dislocation, extensor mechanism rupture, neurovascular compromise, malignancy features)
- Relative rest, ice, compression, elevation in acute soft-tissue injury
- Early guided physiotherapy: quadriceps/hip strengthening, range-of-motion work, proprioception and graded return to activity
- Weight reduction and activity modification for overload or osteoarthritis-pattern pain
- Address biomechanical contributors (footwear, training load, occupational kneeling/squatting adaptations)
Pharmacological Treatment
Simple analgesia
- Paracetamol 1 g orally up to 4 times daily (max 4 g/day in adults)
Use scheduled short-term dosing initially; reduce maximum dose in low body weight/frailty/liver impairment; avoid duplicate paracetamol-containing products.
NSAIDs (oral/topical) with gastroprotection when indicated
- Ibuprofen 400 mg orally three times daily with food (usual max 2.4 g/day prescribed)
- Naproxen 250-500 mg orally twice daily
- Topical ibuprofen gel applied 3-4 times daily to painful area
- Omeprazole 20 mg once daily for GI protection if oral NSAID risk factors
Avoid/caution in CKD, heart failure, uncontrolled hypertension, active peptic ulcer, anticoagulant therapy, or previous NSAID hypersensitivity/asthma exacerbation; use lowest effective dose for shortest duration.
Short-course weak opioid if pain remains severe despite first-line options
- Codeine phosphate 30-60 mg orally every 4-6 hours when required (max 240 mg/day)
Reserve for brief use; counsel on constipation, drowsiness, falls and driving risk; avoid in significant respiratory depression and use caution in older adults.
Condition-specific urgent therapy
- Empirical IV antibiotics for suspected septic arthritis after blood cultures and joint aspirate (for example flucloxacillin local protocol dependent)
Do not delay urgent hospital referral; definitive antibiotic choice should follow local microbiology guidance and culture results.
Surgical / Interventional
- Urgent reduction for patellar dislocation when indicated, then immobilisation/rehabilitation pathway
- Early orthopaedic management of extensor mechanism rupture (quadriceps/patellar tendon repair)
- Fracture fixation according to pattern and stability
- Ligament reconstruction or meniscal surgery in selected persistent instability/mechanical locking cases after specialist assessment
- Arthroplasty for end-stage osteoarthritis with severe symptoms after failed conservative treatment
Complications
- Missed septic arthritis leading to rapid cartilage destruction and sepsis
- Persistent instability after untreated ligament injury
- Chronic pain syndrome/complex regional pain syndrome
- Reduced function, deconditioning and falls
- Post-traumatic or progressive osteoarthritis
- Neurovascular injury complications after major trauma/dislocation
Prognosis
Prognosis depends on cause and timeliness of diagnosis. Many overuse and minor soft-tissue injuries improve with load modification, physiotherapy, and analgesia over weeks to months, whereas delayed recognition of septic arthritis, major ligament/tendon rupture, fracture, or malignancy worsens outcomes. Older age, obesity, recurrent injury, and psychosocial distress increase risk of persistent pain and disability.
Sources & References
✅NICE Guidelines(1)
- Knee pain - assessment[overview]