Is It All About the Fascia? A Systematic Review and Meta-analysis of the Prevalence of Extramuscular Connective Tissue Lesions in Muscle Strain Injury

Abstract

Background: The fascia has been demonstrated to represent a potential force transmitter intimately connected to the underlying skeletal muscle. Sports-related soft tissue strains may therefore result in damage to both structures. Purpose: To elucidate the prevalence of connective tissue lesions in muscle strain injury and their potential impact on return-to-play (RTP) duration. Study Design: Systematic review; Level of evidence, 3. Methods: Imaging studies describing frequency, location, and extent of soft tissue lesions in lower limb muscle strain injuries were identified by 2 independent investigators. Weighted proportions (random effects) were pooled for the occurrence of (1) myofascial or fascial lesions, (2) myotendinous lesions, and (3) purely muscular lesions. Study quality was evaluated by means of an adapted Downs and Black checklist, which evaluates reporting, risk of bias, and external validity. Results: A total of 16 studies (fair to good methodological quality) were identified. Prevalence of strain injury on imaging studies was 32.1% (95% CI, 24.2%-40.4%) for myofascial lesions, 68.4% (95% CI, 59.6%-76.6%) for myotendinous lesions, and 12.7% (95% CI, 3.0%-27.7%) for isolated muscular lesions. Evidence regarding associations between fascial damage and RTP duration was mixed. Conclusion: Lesions of the collagenous connective tissue, namely the fascia and the tendinous junction, are highly prevalent in athletic muscle strain injuries. However, at present, their impact on RTP duration is unclear and requires further investigation.

Is “Delayed Onset Muscle Soreness” a False Friend? The Potential Implication of the Fascial Connective Tissue in Post-Exercise Discomfort

“…As outlined, DOMS primarily occurs during eccentric loading, and during this active lengthening, high strain forces act upon the skeletal muscle. From a functional point of view, the described continuities to the collagenous soft tissue may represent a shock absorber taking up excessive forces potentially damaging the skeletal muscle [46,47]. However, if going beyond the loading capacity, microscopic or macroscopic damage may occur in the endomysium, perimysium, or deep fascia.…”

“…Despite its denomination, muscle injuries rarely affect only the muscle tissue [47]. In about 90% of the cases, the actual site of injury is either located in the musculotendinous junction or in the extramuscular fascia [47].…”

“…Despite its denomination, muscle injuries rarely affect only the muscle tissue [47]. In about 90% of the cases, the actual site of injury is either located in the musculotendinous junction or in the extramuscular fascia [47]. Like DOMS, muscle injury frequently occurs after active excessive eccentric loading, and therefore both may exhibit a similar involvement of the connective tissue.…”

The Structure and Role of Intramuscular Connective Tissue in Muscle Function

“…In the study of advanced human aging, it is unclear if an increase in IMCT concentration is simply a function of muscle fiber volume loss due to inactivity. It is also clear that the connections within muscle tissue afforded by IMCT and myotendinous joint connections are predominant sites of lesions in muscle strain injuries, as highlighted in a recent meta-analysis (Wilke et al, 2019).…”

Fascia Thickness Increases Following Eccentric Exercise Leading to Delayed Onset Muscle Soreness

“…In contrast, structural lesions mostly occur in the connective tissue, namely the myotendinous junction and the deep fascia. Considering that eccentric overload represents the main mechanism of injury, it has been hypothesized that the connective tissue, via its numerous links to muscular structures, absorbs and dampens excessive elongating forces [10].…”