What are the causes and treatment options for knee pain and stiffness in adults?

Causes and Management of Knee Pain and Stiffness in Adults

Osteoarthritis is the most common cause of knee pain and stiffness in adults, particularly those over 45 years, and should be suspected when patients present with activity-related knee joint pain and less than 30 minutes of morning stiffness (95% sensitivity, 69% specificity). 1, 2

Common Causes by Age and Presentation

Adults Over 45 Years

• Osteoarthritis is the predominant cause, affecting an estimated 654 million people worldwide and 32.5 million adults in the US 3, 1, 2
• Characterized by joint pain, stiffness (typically <30 minutes in morning), reduced function, and bony enlargement on examination 1, 2
• Risk factors include age (33% of those >75 years affected), female sex, obesity, genetics, and prior major joint injury 2

Adults Under 40 Years

• Patellofemoral pain syndrome has a lifetime prevalence of approximately 25%, particularly in physically active individuals 1
• Anterior knee pain during squatting is 91% sensitive and 50% specific for this diagnosis 1
• Meniscal tears from acute trauma (twisting injuries) affect an estimated 12% of adults 1
• McMurray test (61% sensitivity, 84% specificity) and joint line tenderness (83% sensitivity, 83% specificity) assist diagnosis 1

Other Important Causes

• Referred pain from hip pathology (pain with internal hip rotation suggests hip OA) 2, 4
• Pes anserine bursitis and medial plica syndrome in active patients 4
• Rheumatoid arthritis and other inflammatory arthropathies (exclude through history and laboratory testing) 5, 6
• Septic arthritis (any age, requires urgent evaluation) 4
• Crystal-induced arthropathy (gout, pseudogout) more common in adults 4

Diagnostic Approach

Key Physical Examination Findings

• Bony enlargement strongly suggests knee OA 2
• Joint line tenderness and positive McMurray test suggest meniscal pathology 1
• Anterior knee pain with squatting indicates patellofemoral syndrome 1
• Effusion and warmth raise concern for inflammatory or infectious causes 4, 5

Imaging Considerations

• Radiographic imaging is NOT recommended for all patients with suspected knee OA 1
• Obtain radiographs when diagnosis is uncertain or to assess severity before surgical referral 3, 1
• Typical radiographic findings include marginal osteophytes and joint space narrowing 2

Treatment Algorithm for Knee Osteoarthritis

First-Line Core Treatments (Offer to ALL Patients)

These core treatments must be offered before considering any pharmacological or surgical interventions. 3

Non-Pharmacological Interventions

• Strengthening exercise and aerobic fitness training are cornerstones of management 3, 1, 2
• Weight loss if overweight or obese (sustained weight loss benefits pain and function) 3, 2
• Self-management education programs such as those by the Arthritis Foundation 3
• Manual therapy (manipulation and stretching) combined with supervised exercise 3, 7
• Local heat and cold applications for temporary symptom relief 3, 7
• Assistive devices to reduce joint loading 3, 7

Exercise Prescription Specifics

• Begin with isometric strengthening at 30% maximal voluntary contraction, gradually increasing to 75% as tolerated 7
• Hold contractions for no longer than 6 seconds 7
• Start with one contraction per muscle group, gradually increasing to 8-10 repetitions 7
• Warm-up phase: 5-10 minutes of low-intensity range-of-motion exercises 7
• Cool-down phase: 5 minutes of static stretching 7
• Static stretching daily when pain minimal, hold terminal position 10-30 seconds 7
• Joint pain lasting >1 hour after exercise indicates excessive activity requiring modification 7

Second-Line Pharmacological Treatments

Only consider after implementing core treatments; prioritize topical over oral agents. 3

Topical Agents (Preferred First)

• Topical NSAIDs (diclofenac gel) are recommended before oral NSAIDs due to markedly reduced systemic exposure and lower risk of gastrointestinal, cardiovascular, liver, and renal toxicity 3, 8, 2
• Particularly advantageous in elderly patients 8
• Capsaicin is an option for localized pain relief 3

Oral Analgesics

• Paracetamol (acetaminophen) at regular doses up to 3000-4000 mg daily (consider 3000 mg limit in older adults) rather than "as needed" for better sustained pain control 3, 7
• Oral NSAIDs or COX-2 inhibitors only if topical treatments fail, using lowest effective dose for shortest duration 3, 7, 2
• All oral NSAIDs have similar analgesic magnitude but vary in gastrointestinal, liver, and cardiorenal toxicity 3
• ALWAYS co-prescribe a proton pump inhibitor with oral NSAIDs for gastroprotection, particularly in middle-aged and older patients 3, 7
• Assess cardiovascular, gastrointestinal, and renal risk factors before prescribing oral NSAIDs 3, 7
• Duloxetine has demonstrated efficacy for OA pain 2

Intra-Articular Injections

• Corticosteroid injections for moderate to severe pain provide short-term relief 3, 7, 2
• Hyaluronic acid is conditionally recommended (evidence mixed) 5
• Platelet-rich plasma lacks sufficient evidence at present 5

Third-Line Adjunctive Treatments

These have less proven efficacy or increased risk compared to second-line options. 3

• Opioids should be avoided but considered cautiously only if previous treatments insufficient and pain prevents sleep 3, 7, 2
• Supports and braces 3
• Shock-absorbing shoes or insoles 3
• Transcutaneous electrical nerve stimulation (TENS) 3

Interventional Procedures (When Conservative Measures Fail)

• Radiofrequency ablation (conventional and cooled) of genicular nerves has been shown effective 5
• Chemical ablation of genicular nerves and neurostimulation lack sufficient evidence currently 5

Surgical Referral

Consider joint replacement surgery only after offering core treatments and when symptoms substantially affect quality of life despite conservative management. 3, 1

Indications for Surgical Referral

• Joint symptoms (pain, stiffness, reduced function) substantially affecting quality of life and refractory to non-surgical treatment 3
• Refer before prolonged and established functional limitation and severe pain develop 3
• End-stage OA with minimal joint space and inability to cope with pain 1

What NOT to Refer For

• Arthroscopic lavage and debridement should NOT be routinely offered unless clear history of mechanical locking (not for gelling, "giving way," or radiographic loose bodies) 3
• Recovery from arthroscopy takes 2-6 weeks with pain, swelling, and limited function 3
• Evidence shows no persistent benefit beyond one year for arthroscopic surgery in degenerative knee disease 3

Patient-Specific Factors

• Age, sex, smoking, obesity, and comorbidities should NOT be barriers to joint replacement referral 3

Treatment for Patellofemoral Pain

Hip and knee strengthening exercises combined with foot orthoses or patellar taping are recommended, with no indication for surgery. 1

Treatment for Meniscal Tears

Conservative Management First

• Exercise therapy for 4-6 weeks is appropriate for most meniscal tears 1
• For degenerative meniscal tears, exercise therapy is first-line treatment; surgery is NOT indicated even with mechanical symptoms (locking, catching) 1

Surgical Indications

• Only for severe traumatic (bucket-handle) tears with displaced meniscal tissue 1

Critical Pitfalls to Avoid

• Do NOT prescribe oral NSAIDs without gastroprotection (proton pump inhibitor) 7
• Do NOT combine topical NSAIDs with oral NSAIDs or other NSAIDs (patients often fail to disclose OTC NSAID use) 9, 8
• Do NOT use glucosamine or chondroitin as evidence does not support efficacy 7
• Do NOT refer for arthroscopic surgery for degenerative knee disease without clear mechanical locking 3
• Do NOT delay surgical referral until severe functional limitation develops 3
• Do NOT exceed 4000 mg daily acetaminophen to prevent hepatotoxicity 7
• Do NOT ignore cardiovascular risk with NSAIDs, even short-term use carries some risk at higher doses 9
• Do NOT use opioids as routine treatment; they should be avoided 2

Special Considerations

Combination Therapy

• Naproxen may be used safely with gold salts and/or corticosteroids 10
• Combination with aspirin is NOT recommended as aspirin increases naproxen excretion rate and may result in higher frequency of adverse events 10

Monitoring During Treatment

• Monitor for NSAID toxicities if treatment extends beyond 10 days 9
• Baseline and periodic monitoring of blood pressure, renal function, and liver function if prolonged NSAID use anticipated 9
• Avoid NSAIDs in high-risk patients: those over 60 years, with cardiovascular disease, renal impairment, history of peptic ulcer disease, or on anticoagulants 9