Introduction
Muscle strains represent 32 % of injuries (1st cause) in footballers (1) and can be opposed to extrinsic muscular injuries resulting from a direct shock.
These lesions arise during an eccentric effort (active contraction occuring simultaneous with lengthening of muscle).
The characterization of muscle strains in footballer is key to guide their therapeutic care.
Ultrasound (US) and MRI,
guided by clinical examination,
are very usefull tools to precisely asses muscle strains.
Topographic and pathologic classification
Topography ( Fig. 1 )
- At the myoconjunctive junction ("m" lesion):
myotendinous junction: proximal or distal.
myofascial junction: central (along an intramuscular conjunctive wall) or peripheral (along epimysium,
which may be between to conjunctive walls).
- Focused on a conjunctive structure ("c" lesion):
Tendon
Intramuscular conjunctive wall
Perimuscular conjunctive wall
Note that lesions focused on a conjunctive wall are underestimated and under-recognized by radiologists and sports physician.
Fig. 1: Topography classification
References: Massein et al. Imaging of muscle injuries The prognosis impact of connective tissue involvement, RSNA poster 2014
Model of bipenned muscle ( Fig. 2)
Bipenned muscles have muscular fibers on both sides of their central conjunctive wall (for example semitendinosus or rectus femoris).
Fig. 14: Grading of muscle strains
References: Massein et al. Imaging of muscle injuries The prognosis impact of connective tissue involvement, RSNA poster 2014
Model of unipenned muscle ( Fig. 3)
Unipenned muscle have muscular fibers on one side of their conjunctive structure (for example,
ending of soleus on calcaneal tendon).
It is more difficult to differentitate "m" and "c" lesions on this model.
The main sign is thickening and hypersignal of the conjunctive structure for "c" lesions.
Some lesions are purely conjunctive,
without muscular hypersignal.For example,
between medial gastrocnemius and soleus,
muscular fibers kiip a correct alignment and are correctly inserted.
The sole abnormality is also located on a conjunctive wall ("c" lesion)