It doesn't. It may improve a bit movement range and reduces stiffness and pain.
When it comes to rheumatoid arthritis, lupus, gout and infectious arthritis there's nothing that passive movement can do due to the etiology of these conditions. Autoimmune arthritis (rheumatoid and lupic) requires immunosupressive therapy. Gout requires lowering uric acid blood levels. Infectious arthritis requires antibiotherapy .
Damage from mechanical stress with insufficient self repair by joints is believed to be the primary cause of osteoarthritis. Sources of this stress may include: misalignments of bones caused by congenital or pathogenic causes; mechanical injury; excess body weight; loss of strength in the muscles supporting a joint; and impairment of peripheral nerves, leading to sudden or uncoordinated movements. However exercise, including running in the absence of injury, has not been found to increase the risk .
Cartilage has limited repair capabilities: Because chondrocytes are bound in lacunae, they cannot migrate to damaged areas. Therefore cartilage damage is difficult to heal. Also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is usually replaced by fibrocartilage scar tissue .
A study made on rabbits in 1980 says that continuous passive movement helps:
At three weeks this assessment revealed that in the adolescent rabbits, healing of the defects by hyaline articular cartilage was present in 5 per cent of forty defects in ten animals whose knees were immobilized, in 9 per cent of forty defects in ten animals whose knees were permitted intermittent active motion, and in 52 per cent of forty defects in ten animals whose knees were managed immediately after operation by continuous passive motion .
However, more recent studies and reviews (although after surgery - when the etiological agent has been removed/suppressed, misalignments have been corrected) fail to confirm that on humans:
There is high-quality evidence that continuous passive motion increases passive knee flexion range of motion (mean difference 2 degrees, 95% CI 0 to 5) and active knee flexion range of motion (mean difference 3 degrees, 95% CI 0 to 6). These effects are too small to be clinically worthwhile. There is low-quality evidence that continuous passive motion has no effect on length of hospital stay (mean difference -0.3 days; 95% CI -0.9 to 0.2) but reduces the need for manipulation under anaesthesia (relative risk 0.15; 95% CI 0.03 to 0.70) .
Continuous passive motion is commonly used postoperatively following cartilage surgery. Unfortunately, the clinical evidence (only 4 studies) to support the use of continuous passive motion is lacking despite an overwhelming abundance of basic science support and the common clinical practice of continuous passive motion implementation postoperatively in knee cartilage restoration procedures. There is a great need for well-conducted, high-level evidence studies to address this void in our literature .
The lack of consistent standardized reporting of postoperative CPM protocols provides an impetus to researchers and clinicians to more clearly define and describe their use following knee articular surgery .
- Wikipedia contributors, "Arthritis," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Arthritis&oldid=615702031 (accessed July 9, 2014).
- Wikipedia contributors, "Osteoarthritis," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Osteoarthritis&oldid=615716855 (accessed July 9, 2014).
- Wikipedia contributors, "Cartilage," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Cartilage&oldid=614202865 (accessed July 9, 2014).
- Salter RB, Simmonds DF, Malcolm BW, Rumble EJ, MacMichael D, Clements ND. The biological effect of continuous passive motion on the healing of full-thickness defects in articular cartilage. An experimental investigation in the rabbit. J Bone Joint Surg Am. 1980 Dec;62(8):1232-51.
- Harvey LA, Brosseau L, Herbert RD. Continuous passive motion following total knee arthroplasty in people with arthritis. Cochrane Database Syst Rev. 2010 Mar 17;(3):CD004260. doi: 10.1002/14651858.CD004260.pub2.
- Fazalare JA, Griesser MJ, Siston RA, Flanigan DC. The use of continuous passive motion following knee cartilage defect surgery: a systematic review. Orthopedics. 2010 Dec 1;33(12):878. doi: 10.3928/01477447-20101021-16.
- Karnes JM, Harris JD, Griesser MJ, Flanigan DC. Continuous passive motion following cartilage surgery: does a common protocol exist? Phys Sportsmed. 2013 Nov;41(4):53-63. doi: 10.3810/psm.2013.11.2036.