Synovial folds in equine articular process joints.
Authors: Thomsen L N, Berg L C, Markussen B, Thomsen P D
Journal: Equine veterinary journal
Summary
# Synovial Folds in Equine Cervical Articular Process Joints Synovial folds—small pouches of synovial membrane within joints—have been implicated as a source of neck pain in human patients, yet their presence and characteristics in equine cervical joints remain poorly documented. Thomsen and colleagues conducted a histological examination of cervical articular process joints (C2/C3 through C6/C7) from six horses, measuring and classifying synovial folds according to tissue type (adipose, fibrous, or mixed) to establish baseline data on their frequency and morphology. Synovial folds were remarkably prevalent, present in 98% of joints examined, with dimensions ranging from 4–41 mm in width and 1–17.8 mm in height; tissue composition varied, with 41% fibrous, 38% adipose and 21% mixed types, whilst fold size was significantly influenced by neck side and fold type. Given these substantial dimensions, synovial folds represent a plausible source of mechanical irritation or entrapment in horses with cervical pain—a consideration particularly relevant when evaluating chronic neck stiffness, resistance to lateral flexion, or acute cervical trauma in clinical practice. Whilst this explorative work is limited to six horses, it provides essential baseline morphological data and suggests that synovial fold pathology warrants further investigation as a differential diagnosis in equine cervical dysfunction.
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Practical Takeaways
- •Cervical synovial folds are nearly universal in horses and may be a normal anatomical feature, but their size suggests they could be involved in neck pain syndromes when damaged
- •Understanding the normal morphology and location of these folds may help explain some cases of unexplained cervical pain or stiffness in practice
- •Further research is needed to determine which horses with synovial folds develop clinical problems and under what circumstances they become symptomatic
Key Findings
- •Synovial folds were identified in 98% of cervical articular process joints examined across C2-C7 levels
- •Synovial fold width ranged from 4-41 mm and height from 1-17.8 mm, with significant variation by neck side and fold type
- •38% of folds were adipose type, 41% fibrous type, and 21% mixed type
- •Size of synovial folds indicates potential for damage from acute injury or chronic cervical articular process joint disease