Knee Osteoarthritis

Patients describe activity-related mechanical knee pain that eases with rest, with morning or post-rest gelling stiffness lasting under 30 minutes. Stairs (especially descending), squatting, and rising from a low chair are typically the worst. Intermittent effusions follow increased activity, and giving way is usually pain inhibition or quadriceps weakness rather than true ligamentous instability. Patellofemoral disease produces anterior knee pain worsened by prolonged sitting (the cinema sign).

On examination, look for antalgic gait, varus or valgus alignment, lateral thrust in stance (suggesting medial compartment loss), and quadriceps wasting. Palpate for joint-line tenderness, patellofemoral tenderness, and effusion using the patellar tap or sweep test. Document any fixed flexion deformity and crepitus through range. Test collateral and cruciate stability since secondary laxity develops with compartmental collapse. Examine the hip in every case: hip OA refers pain to the knee, and disproportionately mild knee findings should redirect the examination.

Knee OA is a clinical diagnosis per NICE NG226 in adults aged 45 and over with activity-related pain and morning stiffness of 30 minutes or less. Routine imaging is not required.

When imaging is justified by diagnostic uncertainty, atypical presentation, or pre-operative planning, request weight-bearing AP and lateral radiographs with a skyline view for the patellofemoral joint. Non-weight-bearing films underestimate joint space narrowing. Classical features are joint space narrowing, subchondral sclerosis, osteophytes, and subchondral cysts. Chondrocalcinosis raises suspicion of CPPD. Radiographic severity correlates poorly with symptoms.

Bloods are reserved for suspected inflammatory or crystal disease. MRI is not first-line and commonly shows degenerative meniscal tears, which are part of the OA process. Aspirate any acutely hot, swollen, painful knee for microscopy, culture, and crystal analysis.

Management follows NICE NG226 (2022). Offer core treatments to everyone: structured education that reframes OA as manageable and avoids wear and tear or bone on bone language, tailored therapeutic exercise, and weight management for those with overweight or obesity. A 5 to 10% weight reduction produces clinically meaningful improvement. Consider manual therapy only alongside exercise.

The pharmacological first line is a topical NSAID, which NG226 specifically recommends offering for the knee (stronger wording than for other joints), and should be tried before any oral preparation. If topical NSAIDs fail, consider a short course of oral NSAID at the lowest effective dose with gastroprotection. Paracetamol and weak opioids are no longer routinely recommended, a change from the 2014 guideline. Do not offer strong opioids, glucosamine, chondroitin, intra-articular hyaluronan, acupuncture, electrotherapy, or lateral wedge insoles. Intra-articular corticosteroid injection is reasonable for short-term symptom relief or to support exercise engagement, with diabetic patients warned about transient hyperglycaemia.

Refer for joint replacement when quality of life is substantially affected despite non-surgical care. Do not use a specific X-ray grade, BMI, age, smoking status, or comorbidity as a barrier. Surgical options include TKR (most common), UKR for selected unicompartmental disease, and HTO for younger patients with isolated medial compartment OA and varus alignment. Arthroscopic lavage, debridement, and partial meniscectomy for degenerative tears in OA are explicitly not recommended (ESCAPE, FIDELITY).

Exercise is the cornerstone. Progressive quadriceps strengthening targets both open-chain work (straight leg raises, terminal knee extension) and closed-chain work (mini squats, leg press, step-ups, wall sits). Combine with hip abductor strengthening, particularly gluteus medius which reduces medial compartment loading, hamstring work, and range of motion exercises with priority on maintaining full extension. Aerobic conditioning through walking, cycling, swimming, or aquatic exercise supports weight management and general fitness. Aquatic exercise is particularly useful for patients with severe symptoms who cannot tolerate land-based loading.

Pair exercise with dietary support since 5 to 10% weight loss yields clinically meaningful symptom reduction. A walking stick in the contralateral hand offloads the affected side.

Prehabilitation before TKR follows GIRFT principles: quadriceps strengthening, aerobic fitness, weight optimisation, smoking cessation, anaemia correction, diabetic optimisation, and expectation setting. Post-TKR rehabilitation uses enhanced recovery pathways with day-of-surgery mobilisation, full weight-bearing as tolerated, and progressive ROM where regaining full extension is the priority. Aim for 0 degrees extension and 90 plus degrees flexion by six weeks. Falls prevention should be considered for older patients with reduced confidence on stairs.

• •NICE NG226 (2022): Knee OA is a clinical diagnosis in adults aged 45+ with activity-related pain and morning stiffness of 30 minutes or less; education, exercise, and weight management are the core treatments.
• •NICE NG226 (2022): Specifically recommends offering a topical NSAID for the knee before any oral preparation; paracetamol and weak opioids are no longer routinely recommended.
• •ESCAPE trial (Katz, 2013, NEJM): Arthroscopic partial meniscectomy plus physiotherapy was not superior to physiotherapy alone for degenerative meniscal tears with concurrent knee OA.
• •FIDELITY trial (Sihvonen, 2013, NEJM): Arthroscopic partial meniscectomy was not superior to sham surgery for degenerative meniscal tears in middle-aged patients.
• •GIRFT Orthopaedic report: Sets best-practice elective arthroplasty pathways for the NHS, including prehabilitation and enhanced recovery.

• •NICE NG226 makes knee OA a clinical diagnosis at age 45+ with activity-related pain and morning stiffness of 30 minutes or less; routine imaging is not required.
• •Morning stiffness over 30 minutes points to inflammatory arthritis rather than OA. One of the most commonly tested distinctions.
• •NG226 offers a topical NSAID for the knee before any oral NSAID. Paracetamol is no longer first-line, a frequent exam trap from the 2014 to 2022 change.
• •Arthroscopic lavage, debridement, and partial meniscectomy for degenerative meniscal tears in OA are explicitly not recommended (ESCAPE, FIDELITY).
• •Hip OA refers pain to the knee. If knee examination is disproportionately normal, examine the hip before imaging.
• •Do not exclude patients from joint replacement referral on the basis of age, BMI, smoking, or comorbidities.