recovery. These results confirm the first hypothesis that
only recent-onset knee flexion contractures fully reverse
spontaneously. This study confirmed reports of incomplete
reversal of joint contractures in various animal models
[11-16] and improved upon previous investigations
by the broad range of 18 clinically relevant durations of
spontaneous recovery, from adult to geriatric age, by standardized
mechanical testing, and by sufficient sample size
for statistical testing. These data should help resolve the
controversy regarding the potential for full spontaneous
recovery of joint contractures secondary to immobility
[8,10].
Within a specific time window — recovery for 2–8
weeks, some knee joint contractures were partially reversible.
The extent of partial reversal was modest, an
average gain of 20° of knee extension. This corresponded
to an average 41% of the contractures (Figure 1). These
constituted plateaus in the spontaneous recovery; extending
the duration of recovery never led to a significant
improvement of the contractures, which confirms the second
hypothesis. Once a joint contracture is diagnosed, the
current study implies that simple observation is not an appropriate
option. Our data predict a poor prognosis, with
recovery of only 20° (or 41%) of the contracture. Therefore
intervention may be necessary to regain knee extension
beyond natural recovery.
This study also measured decreased knee extension
over time in the rat knees contralateral to a contractured
knee (Figure 1). In this animal model, at least three factors
can contribute: both surgical procedures involved
general anesthesia and postoperative recovery (approximately
1 week each). The temporary general hypomobility
may have contributed to the loss of extension in