Continuous Passive Motion after Knee Replacement Surgery

A Plain Language Summary

Background:

Knee replacement surgery is common for the management of arthritis, but can cause knee stiffness. Knee stiffness can make it difficult to perform certain activities including standing up from a seated position. Continuous passive motion (CPM) is a way of providing regular movement to the knee using a machine. This research review presents what we know about the effects of CPM following knee surgery. After searching for all relevant studies through January 2013, the research team at The Cochran Collaboration found 24 studies with 1445 participants who had knee replacement surgery primarily for knee arthritis.

Continuous Passive Motion Device

Here is a link to the Cochrane Collaboration Study (2014): Continuous passive motion after knee replacement surgery

Below we review the findings.

CPM was started from the first to the fourth day post surgery and applied for 1.5 to 24 hours a day, over 1 to 17 days. In the study it was found that CPM following knee replacement surgery may improve the ability to bend the knee slightly. But it does not improve pain or function. The results were inconclusive about the effects of CPM on need for Manipulation Under Anesthesia, participants’ perceptions of treatment effectiveness, or risk of complications.

The best estimates of what happens to people who have CPM after knee replacement surgery are:

Range of Motion – active knee flexion (i.e. ability to bend the knee)

People who had CPM were able to bend their knees an average of 2 degrees more (0 to 5 degrees more) than those who did not have CPM at six weeks (2% absolute improvement, 0 to 4% absolute improvement)

– Those who had CPM were able to bend their knees an average of 80 degrees.

– People who did not have CPM were able to bend their knees an average of 78 degrees.

Pain (higher scores means worse or more severe pain)

People who had CPM rated their pain an average of 0.4 points lower (0.8 points lower to 0.1 points higher) on a 0 to 10 point scale at six weeks (4% absolute reduction, 8% reduction to 1% increase)

– Those who had CPM rated their pain an average of 2.6 points on a 0 to 10 scale.

– People who did not have CPM rated their pain an average of 3 points on a 0 to 10 scale.

Function (higher scores means better function)

People who had CPM had a loss in function equivalent to an average of 1.6 points on a 0- to 100-point scale at six months (2% absolute reduction, 5% reduction to 2% increase).

– Those who had CPM had function equivalent to an average of 56 points on a 0- to 100-point scale.

– People who did not have CPM had function equivalent to an average of 57.6 points on a 0- to 100-points scale.

Quality of life (higher scores means better quality of life)

People who had CPM had an increase in quality of life equivalent to an average of 1 point on a 0- to 100-point scale at six months (1% absolute improvement, 3% reduction to 4% increase).

– Those who had CPM had a quality of life equivalent to an average of 41 points on a 0- to 100-point scale.

– People who did not have CPM had function equivalent to an average of 40 points on a 0- to 100-points scale.

Manipulation Under Anesthesia

People who had CPM had a decrease in the risk of requiring manipulation under anesthesia equivalent to an average of 25 fewer manipulations per 1000 patients (4% absolute risk reduction, 8% risk reduction to 0% risk reduction).

Adverse Events

People who had CPM had a decrease in the risk of developing adverse events equivalent to an average of 13 fewer adverse events per 1000 patients (1% absolute risk reduction, 5% risk reduction to 3% risk increase).

– Those who had CPM had on average a 15% risk of developing adverse events.

– People who did not have CPM had on average a 16.3% risk of developing adverse events.

Comparison: CPM and PMKR Machine

Here is an analysis of the CPM as compared to a new class of knee rehabilitation devices known as PMKR – Pressure Modulated Knee Rehabilitation. The X10 is the first PMKR machine.

The Global Journal of Orthopedics Research: Are Computer-Controlled, Pressure Modulated Knee Rehabilitation Machines Valuable Following Knee Arthroplasty?

knee exercise machine - X10 4.0 Knee Machine