Publications

Background: People with haemophilia (PwH) are prone to joint bleeds resulting in haemophilic arthropathy (HA), potentially altering muscle tissue. While functional and morphological impairments are documented, little is known about biomechanical muscle properties in PwH.

Objectives: This study investigates muscle stiffness in relaxed and contracted states in the lower limbs of adult PwH and its relationship to muscle strength and joint health.

Methods: In this cross-sectional case-control study, 40 PwH and 20 healthy controls were assessed. Using myotonometry, stiffness of eight lower limb muscles was measured under relaxed (S_rel) and maximum voluntarily contracted conditions (S_con). Stiffness increase rate (SIR) was calculated. Joint health was assessed via the Haemophilia Joint Health Score (HJHS) and sonography (HEAD-US), muscle strength was measured using a mobile isometric force gauge. PwH were stratified by lower limb joint impairment (PwH_minor vs. PwH_major).

Results: PwH_major exhibited significantly increased S_rel in anterior thigh and calf muscles compared to controls and PwH_minor (all p ≤ .05, r = .397 to .101). Under contraction, PwH_major showed reduced S_con in the tibialis anterior (p ≤ .05, r = .511 to 683) and biceps femoris (p = .041, r = .390). The SIR was significantly lower in PwH_major across most muscles (all p ≤ .05, r = .380 to .573), indicating impaired muscle contractility. Furthermore, muscle strength correlated negatively with S_rel (rs = -0.220 to -0.430) and positively with both S_con and SIR (rs = 0.273 to 0.449). HJHS correlated with myotonometric parameters (rs = 0.248 to 0.683), linking joint damage to altered muscle properties.

Conclusion: Advanced HA is associated with increased passive stiffness and reduced active muscle response, particularly in stabilizing muscle groups. Myotonometry may serve as a potential supplementary tool for the exploratory assessment of biomechanical muscle status in PwH.

Keywords: haemophilic arthropathy, muscle stiffness, muscle strength, myotonometry

This study provides first detailed insights into the biomechanical viscoelastic muscle properties of adult PwH using non-invasive myotonometry. The findings reveal that PwH with advanced HA exhibit increased muscle stiffness at rest S_rel and reduced stiffness during maximal voluntary contraction S_con, particularly in muscle groups responsible for stabilizing the commonly affected knee and ankle joints. The differences observed in the SIR between PwH_major, PwH_minor, and CG suggest structural and functional alterations in skeletal muscle associated with the severity of HA. Furthermore, the correlations between myotonometric parameters and muscle strength underscore the functional relevance of these biomechanical properties, highlighting a progressive loss of muscle function in PwH with advanced joint damage.

However, given the observational cross-sectional design of this study, causal relationships cannot be established and statements regarding direct clinical implementation must be made with caution. Future longitudinal and interventional research is required to determine whether myotonometric monitoring can effectively guide clinical decision making or individual therapy planning.