Assessing Foot Loads in Continuous Passive Motion (CPM) and Active Knee Joint Motion Devices

Area of Science:

• Orthopedics
• Biomechanics
• Rehabilitation Engineering

Background:

• Continuous passive motion (CPM) and active knee joint motion devices are widely used post-surgery.
• Limited data exists comparing plantar loads between these mobilization techniques.
• Investigating foot loads is crucial for understanding device efficacy and patient recovery.

Purpose of the Study:

• To measure and compare plantar foot loads during knee joint mobilization using CPM and active devices.
• To compare these loads against the physiological load of full weight-bearing during normal gait.
• To evaluate the impact of different resistance levels and range of motion settings on foot loading.

Main Methods:

• Fifteen healthy participants underwent testing with CPM and active knee motion devices.
• Plantar loads were measured using dynamic pedobarography with the pedar® X system.
• Devices were tested with restricted (0-0-90°) and free range of motion, and active devices included four resistance levels.

Main Results:

• CPM devices generated negligible plantar forces (< 1.5 N).
• Active devices with restricted ROM produced < 1.5 N (0-II resistance) and 3.4 N (III resistance).
• Active devices with free ROM generated 0.6% to 1.1% of full weight-bearing loads, with peak forces around 7.7 N.

Conclusions:

• Both CPM and active knee motion devices allow for exercises under strict weight-bearing restrictions.
• Active devices can be utilized for offloading the ankle and foot joints.
• Further research on intra-articular joint loads is recommended to validate these findings.