Trauma can breach the integrity of the joint capsule and result in infection, long-term arthritis, and other serious and potentially permanent morbidity. Synovial joint fluid provides nutrition to the articular cartilage. Loss of synovial fluid without prompt joint capsule closure can lead to cartilage wasting. Additionally, any breach of the joint capsule, especially through dirty skin, can introduce environmental contaminants and risk septic inoculation of the joint. The injection of joints with methylene blue dye is a simple, rapid, and definitive way to assess joint capsule integrity in cases of periarticular trauma where the clinical examination is inconclusive.
Synovial joints, such as those of the fingers, wrist, shoulder, and knee, consist of a fibrous capsule that overlies a thin, delicate synovial membrane (Figure 78-1). The synovial membrane is a highly vascular structure and the site of synovial fluid production. The synovial fluid provides nutritional support to the relatively avascular articular cartilage. Joint capsules contain varying volumes of fluid, and can be greatly expanded under conditions of inflammation or injection.
The anatomy of the knee joint.
Methylene blue is a relatively safe and stable deep blue dye used in both chemistry and medicine. It has most frequently been used to treat methemoglobinemia and for marking skin and lymphatic tracts for oncologic surgery. It is readily oxidized, which has been the proposed basis for its vasoconstrictive effects.1 Methylene blue can cause local necrosis without an immune sensitization when injected at full strength directly into tissues.2
The literature regarding the safety of methylene blue, even during direct intradermal injection, is supportive of its use. When used for lymph node mapping (i.e., direct intradermal and intraparenchymal injection), there is consistent evidence of local inflammatory reactions ranging from local wheal and flare (0.5% of patients) to focal erythema with induration (5% of patients).3,4 Superficial tissue toxicity occurred in only 1.25% of patients.4 These reactions were proportional to the concentration of methylene blue dye (ranging from a dilution of 1:1 to 1:7) and the superficiality of the injection.4 Emergency Physicians (EPs) need to be aware of the potential complications arising from its use just as with any drug or dye introduced parenterally or intradermally. The tissue toxic effects are believed to be much less for intra-articular injections than direct intradermal injection.
The primary indication for injecting a joint with methylene blue dye is to assess the integrity of the articular joint capsule (Figure 78-2). This includes any of the following injuries in close proximity to a joint: skin laceration, a visible joint capsule through a wound, an open fracture, extravasation of serous or serosanguineous fluid from a wound, or a traumatic loading of the joint with evidence of a deformity or an acute effusion. The finger, wrist, elbow, shoulder, toe, ankle, knee, and ...