Sports-related changes of the synovial membrane

Abstract

Purpose: the aim of this study is to differentiate the behavior of the synovial membrane in the presence of various stimuli in patients who practice sports.

Methods: fifty one patients (30 males and 21 females, mean age 48 years, range 31-59 years) who actively practiced non-competitive sports underwent a biopsy of the synovial membrane during arthroscopic surgery performed for joint effusion secondary to meniscal lesion (24 cases), anterior cruciate ligament injury (ACL) (17 cases), postoperative knee joint stiffness (2 cases), aseptic loosening or dislocation of the polyethylene component of uni-compartmental knee arthroplasty (5 cases), and anterior fibrous impingement of the ankle (3 cases). Synovial tissue samples were obtained during surgery from all the patients and processed for light microscopy, transmission electron microscopy and scanning electron microscopy observation.

Results: circulatory phenomena were observed in acute inflammatory processes, characterized by hyperemia and vasodilation. Exudative and infiltrative phenomena were observed in the presence of foreign bodies and were characterized by leukocytic exudation (presence of polynuclear neutrophils), accompanied by lymphomonocytic infiltration. Proliferative phenomena were observed in post-traumatic forms of synovitis (ACL and meniscal injuries), characterized by hypertrophy and proliferation of villous formations. Degenerative and regressive phenomena were observed in cases of fibrous reaction (ankle impingement and joint stiffness) and were characterized by formation of dense fibrous connective tissue with hyaline patches, evolving towards sclerosis.

Conclusions: the activation of inflammatory processes in patients who expose their joints to excessive stress may lead to the formation of hyperplastic tissue. Ultramicroscopic debris is usually capable of transforming the structural organization of the synovial tissue.

Level of evidence: Level IV, observational case series.

Keywords: athlete; sports; synovial membrane; synovitis; ultrastructure.

Fig. 1

A: Post-traumatic subacute arthrosynovitis: the vascular congestion of the villi is easily seen during arthroscopy procedures. B: The intimal hyperplasia of the lining, supported by the accumulation of synoviocytes is indicative of an injury dating back at least 2–3 weeks.

Fig. 2

The penetration of the synovial tissue (reparative function expression) within the mesh of the tendon tissue (synovialization process) allows the revascularization and colonization of graft. The type B synoviocytes are the main responsible for the repopulation of the graft.

Fig. 3

Chronic hypertrophic proliferative synovitis.

Fig. 4

A: Arthroscopic examination has allowed us to highlight a dark gray pannus, proliferative, which surrounds the whole joint with the release of a number of metal beads. B: Detail of villus giant piece: numerous pieces of metal inside. C: The histological examination shows the debris of metal, in the form of aggregated blacks within the synovial membrane lined with fibrous connective tissue. D: The transmission electron microscopy shows that small fragments of metal (white arrow) are phagocytosed by macrophages. E: The largest metallic debris are indigestible and remain in the interstitium.

Fig. 5

A: Arthroscopic view of an artificial ligament broken 1 year by the implantation; it’s possible to appreciate the wear fragments become detached from the synthetic ligament. B: Severe structural disruption of the synovial membrane, especially in the zones of rupture of the ligament. C: Synovial tissue with aspects of papillary hyperplasia, chronic inflammatory pictures, hemosiderin deposit of material and fragments of ligament. D: The task of debris removal is carried mainly by type A synoviocytes, which are able to degrade the material to be deleted.

Fig. 6

A: Chronic hyperplastic arthrosynovitis of prevailing inflammatory and reactive. B: The histological examination demonstrated the presence of hemosiderin pigment and villous hyperplasia: these findings do not constitute sufficient evidence to make a diagnosis of SVNP it is in fact necessary to the complete subversion of the structural response of typical granulomatous formations.

Fig. 7

A: The alignment of the fibers is subverted; available anarchist fibroblast. B: Appearance arthroscopic intra-articular fibrosis, proliferation of tissue adhesions at the level of the fornix may limit joint movement.