Osteoarthritis (Knee OA)

🔍 When to Suspect

A patient aged 45 or over presents with activity-related knee pain and no morning stiffness, or stiffness that lasts less than 30 minutes

From the full topic in The Ocean Library: Osteoarthritis (Knee OA)

🧭 When to suspect

Osteoarthritis (OA) is the most common form of arthritis and the knee is one of the most frequently affected joints – a leading cause of pain and disability in older adults, and overwhelmingly managed in primary care. It is a whole-joint "wear and repair" process involving cartilage loss, bony remodelling and low-grade synovial change, and the degree of damage on X-ray correlates poorly with how much pain a person has.

The diagnosis is clinical. Under NICE NG226, diagnose knee osteoarthritis without imaging in a person who is 45 or over, has activity-related joint pain, and has either no morning joint-related stiffness or morning stiffness lasting no longer than 30 minutes. Imaging is not needed to confirm the diagnosis and should be reserved for atypical features.

The key primary-care skills are twofold: recognise the mechanical pattern (pain worse with use, eased by rest), and never miss an inflammatory or septic mimic. Raise suspicion in those with increasing age, overweight or obesity (the main modifiable risk factor), previous joint injury or surgery (e.g. meniscectomy, anterior cruciate ligament rupture), occupations involving heavy lifting or repetitive kneeling/squatting, a family history of OA, and in women, in whom knee OA is more common.

Points towards osteoarthritis	Atypical features – reconsider the diagnosis
• Age ≥ 45 with gradual-onset, activity-related pain (worse with use, better with rest)	• Hot, red, swollen, acutely painful joint – think septic or crystal arthritis
• No morning stiffness, or stiffness ≤ 30 minutes	• Prolonged morning stiffness > 30 minutes, or pain worse at rest and easing with movement – think inflammatory arthritis
• Crepitus, bony swelling and restricted movement	• Rapidly worsening pain, function or deformity, or marked systemic upset
• Functional limitation (stairs, walking, kneeling) without systemic illness	• Rest/night pain with weight loss or a history of cancer (bone pathology), or true locking (meniscal tear / loose body)

Source: NICE NG226

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