Abstract
Background: Knee flexion contractures prevent the full extension of the knee joint and cause disability. The
etiology is not well defined. Extended periods of immobilization of joints lead to contractures difficult to
completely reverse by rehabilitation treatments. Recovery of the complete range of motion without intervention
has not been studied but is of importance to optimize clinical management. This study was designed to quantify
the spontaneous reversibility of knee flexion contractures over time.
Methods: Knee flexion contractures of increasing severities were induced by internally fixing one knee of 250 adult
male rats for 6 increasing durations. The contractures were followed for four different durations of spontaneous
recovery up to 48 weeks (24 groups, target n = 10 per group). The angle of knee of extension at a standardized
torque was measured. Contralateral knees constituted controls.
Results: Full reversibility characterized by knee extension similar to controls was only measured in the lowest
severity group where 4 weeks of spontaneous recovery reversed early-onset contractures. Spontaneous recovery of
2, 4 and 8 weeks caused partial gain of knee extension in longer-lasting contractures (P ≤ 0.05; all 4 comparisons).
Extending the durations of spontaneous recovery failed to further improve knee extension (P > 0.05, all 12
comparisons). No reversal occurred in the highest severity group (32 week; P > 0.05).
Conclusions: Reversibility of knee flexion contractures was dependent on their severity. Full spontaneous recovery
was limited to the least severe contractures. While contractures initially improved, a plateau was reached beyond
which additional durations of spontaneous recovery led to no additional gain of knee extension. These
results support our view that without treatment, permanent losses in knee mobility must be anticipated in
immobility-induced contractures.
Keywords: Contracture, Knee joint, Biomechanics, Reversibility, Temporal study