Knee osteoarthritis pendulum therapy: In vivo evaluation and a randomised, single-blind feasibility clinical trial

Abstract

Background: Exercise is recommended as the first-line management for knee osteoarthritis (KOA); however, it is difficult to determine which specific exercises are more effective. This study aimed to explore the potential mechanism and effectiveness of a leg-swinging exercise practiced in China, called 'KOA pendulum therapy' (KOAPT). Intraarticular hydrostatic and dynamic pressure (IHDP) are suggested to partially explain the signs and symptoms of KOA. As such this paper set out to explore this mechanism in vivo in minipigs and in human volunteers alongside a feasibility clinical trial. The objective of this study is 1) to analyze the effect of KOAPT on local mechanical and circulation environment of the knee in experimental animals and healthy volunteers; and 2) to test if it is feasible to run a large sample, randomized/single blind clinical trial.

Methods: IHDP of the knee was measured in ten minipigs and ten volunteers (five healthy and five KOA patients). The effect of leg swinging on synovial blood flow and synovial fluid content depletion in minipigs were also measured. Fifty KOA patients were randomly divided into two groups for a feasibility clinical trial. One group performed KOAPT (targeting 1000 swings/leg/day), and the other performed walking exercise (targeting 4000 steps/day) for 12 weeks with 12 weeks of follow-up.

Results: The results showed dynamic intra-articular pressure changes in the knee joint, increases in local blood flow, and depletion of synovial fluid contents during pendulum leg swinging in minipigs. The intra-articular pressure in healthy human knee joints was -11.32 ± 0.21 (cmH₂O), whereas in KOA patients, it was -3.52 ± 0.34 (cmH₂O). Measures were completed by 100% of participants in all groups with 95-98% adherence to training in both groups in the feasibility clinical trial. There were significant decreases in the Oxford knee score in both KOAPT and walking groups after intervention (p < 0.01), but no significant differences between the two groups.

Conclusion: We conclude that KOAPT exhibited potential as an intervention to improve symptoms of KOA possibly through a mechanism of normalising mechanical pressure in the knee; however, optimisation of the method, longer-term intervention and a large sample randomized-single blind clinical trial with a minimal 524 cases are needed to demonstrate whether there is any superior benefit over other exercises.

The translational potential of this article: The research aimed to investigate the effect of an ancient leg-swinging exercise on knee osteoarthritis. A minipig animal model was used to establish the potential mechanism underlying the exercise of knee osteoarthritis pendulum therapy, followed by a randomised, single-blind feasibility clinical trial in comparison with a commonly-practised walking exercise regimen. Based on the results of the feasibility trial, a large sample clinical trial is proposed for future research, in order to develop an effective exercise therapy for KOA.

Keywords: Clinical trials; Intraarticular pressure; Knee osteoarthritis (KOA); Knee osteoarthritis pendulum therapy (KOAPT).

Graphical abstract

Fig. 1

The design of the study. A, In vivo study of the intraarticular hydrostatic pressure of the knee and the effect of leg swinging on the intraarticular dynamic pressure, synovial blood flow and depletion of synovial fluid contents. B1, intra-articular hydrostatic pressure of healthy volunteers and KOA patients, and intra-articular dynamic pressure of healthy volunteers. B2, a randomised, single-blind feasibility clinical trial.

Fig. 2

Dynamic pressure changes of knee joint pressure during leg pendulum swinging (mean ± SE, unit: cmH₂O).

Fig. 3

The effect of leg pendulum movement on knee synovial blood flow immediately after a 6-min exercise by electrical stimulation (Active swing) group, the no leg exercise in the same animal (Control-A); or 6 min exercise by mechanical pushing (Passive swing) and the no exercise leg in the same animal (Control-P). There were 7- and 5-fold increases of knee synovial blood flow 30 s after exercises in both the active and passive swing groups in comparison with their respective control groups (p < 0.05). The increases of synovial blood flow recovered to less than a 2-fold increase in 3.5 min.

Fig. 4

The effect of leg pendulum movement on potential synovial content depletion. Control, control group with gadopentetate meglumine injection without exercise. L(Ga)-L(Swing), gadopentetate was injected into the left knee joint cavity followed by 2 × 6 min left leg pendulum movement. L(Ga)-R(swing), gadopentetate was injected into the left knee joint cavity followed by 2 × 6 min right leg pendulum movement. Gadopentetate injected into the knee joint cavity was rapidly depleted and released into the blood at the end of the first swing and reached a peak at the end of the second swing movement. Both control and L(Ga)-R(swing) animals showed slow release of gadopentetate into the blood at 6 min. At the second swing the gadopentetate in the L(Ga)-R(swing) group slowly increased and peaked at 42 min, whereas the control group maintained a slow release.

Fig. 5

Healthy and KOA joint pressure (mean ± SE, unit: cmH₂O).

Fig. 6

Dynamic pressure changes of knee joint pressure during leg pendulum swinging of healthy human volunteers (mean ± SE, unit: cmH₂O).

Fig. 7

The flow of patients in the trial.

Fig. 8

The number of swings for all participants as an average with associated 95% confident intervals, whereby across all KOAPT group participants, the target of 1000 swings per day was, on average, achieved by day 58, with a group average increase of 7.1 swings/day (R² = 0868).