Why is knee OA important? Affects one-fifth of the US population and is one of the most common causes of pain and disability.

Knee OA is the most prevalent form of OA in women (13%) and men (10%) over 60.

Presentation: knee pain that worsens with prolonged activity, crepitus on exam.

If just OA, the aspirate will reveal a clear synovial fluid with a white blood cell count less than 2000 per uL, an ESR <40 and rheumatoid factor less than 1:40.

You can also aspirate the knee if you palpate an effusion and want to send for inflammatory or infectious arthritis work-up.

X-rays really aren’t necessary if the story fits. But you will see joint space narrowing, bony spurs, subchondral sclerosis/thickening.

If you’re concerned about inflammatory or infectious process consider X-ray, aspiration and lab testing.

Combination of age > 50, presence of bony enlargement, crepitus and no palpable warmth is 92% sensitive and 75% specific for knee OA with a positive likelihood ratio of 3.7.

Weight loss for BMI > 25 through calorie restriction and exercise.

Exercise therapy: no recommended strategy other than self-management programs that include strengthening, low impact aerobic exercise and neuromuscular education.

Cochrane review in 2015 of 54 randomized clinical trials showed some benefit in pain and function with land-based exercises as opposed to aquatic exercise.

Cochrane review in 2016 of 13 aquatic therapy vs control in randomized control trials did find improvement in pain, disability and quality of life but did disappear after 4-24 weeks post-intervention.

Bracing/wedge inserts/taping: limited evidence of effectiveness.

Acetaminophen: number needed to treat between 4 and 16 but this is based on Cochrane review from 2006 that showed those taking properly dosed (1000mg, 4 times a day) improved 4 points on a 100 point scale.

American College of Rheumatology still recommends as initial management but American College of Orthopedic Surgeons no longer recommends for or against it.

NSAIDs:

There doesn’t seem to be a superior NSAID.

Be careful in older patients, those with a history of GI bleed and definitely stay away if they have Stage 4 or 5 kidney disease.

Topical NSAIDs may be just as effective as oral agents with less GI side effects.

Check out the July 2017 PCRAP Paper Chase for more details on topical NSAIDs.

Tramadol:

Cochrane review of 10 randomized trials showed only small benefit (8 points on 100 point scale).

Cepeda MS et. al. Tramadol for osteoarthritis. Cochrane Database Syst Rev. 2006 Jul 19;(3):CD005522. Review. PMID: 16856101.



Opioids:

Minimal benefit (0.7 on a 10-point scale) with high risk potential.

da Costa BR et. al. Oral or transdermal opioids for osteoarthritis of the knee or hip. Cochrane Database Syst Rev. 2014 Sep 17;(9):CD003115. PMID: 25229835.

Chondroitin sulfate:

Data is mixed - Cochrane review in 2015 looked at 800mg per day v. placebo and found pain reduction at less than 6 months, 10 points on a 100 point scale and number needed to treat of 5.

Singh JA et. al. Chondroitin for osteoarthritis. Cochrane Database Syst Rev. 2015 Jan 28;1:CD005614. PMID: 25629804.



American Academy of Orthopedic Surgeons recommends against using glucosamine for treatment of knee OA.

Duloxetine: three studies have shown improvement in pain with number needed to treat of 5 for 50% pain improvement. Data for widespread use is not available.

Steroid injections: Have been used since the 1950’s but the data is limited.