Bakers cysts arise between the tendons of the medial head of the gastrocnemius and the semimembranosus muscles. They are posterior to the medial femoral condyle. The synovial sac of the knee joint can, under certain circumstances, produce a posterior bulge, into the popliteal space, the space behind the knee. When this bulge becomes large enough, it becomes palpable and cystic. Most Bakers cysts maintain this direct communication with the synovial cavity of the knee, but sometimes, the new cyst pinches off. A Bakers cyst can rupture and produce acute pain behind the knee and in the calf and swelling of the calf muscles. Diagnosis
Diagnosis is by examination. A Bakers cyst is easier to see from behind with the patient standing with knees fully extended. It is most easily palpated (felt) with the knee partially flexed. Diagnosis is confirmed by ultrasonography, although if needed and there is no suspicion of a popliteal artery aneurysm then aspiration of synovial fluid from the cyst may be undertaken with care. An MRI image can reveal presence of a Bakers cyst. An infrequent but potentially life-threatening complication, which may need to be excluded by blood tests and ultrasonography, is a deep vein thrombosis (DVT). Quick assessment of the possibility of DVT may be required where a Bakers cyst has compressed vascular structures, causing leg edema, as this sets up conditions for a DVT to develop. A burst cyst commonly causes calf pain, swelling and redness that may mimic thrombophlebitis. Treatment
Bakers cysts usually require no treatment unless they are symptomatic.
One exception is barodontalgia manifested as referred pain from barosinusitis or barotitis-media. The latter two conditions are generated from pressure changes rather than pressure-related flare-up of pre-existing conditions. A meta-analysis of studies conducted between 2001 and 2010 revealed a rate of 5 episodes/1,000 flight-years. Maxillary and mandibular dentitions were affected equally in flight, but in diving, maxillary dentition was affected more than the mandibular dentition, which can indicate a greater role for maxillary sinus pathology in diving barodontalgia. Surprisingly, despite cabin pressurization, the current in-flight barodontalgia incidence is similar to the incidence in the first half of the 20th century. Also, despite the greater fluctuation in divers pressures, the weighted incidence of barodontalgia among aircrews is similar to the weighted incidence among divers. Furthermore, contrary to common belief, and in contrast to diving conditions, the role of facial barotrauma in the cause of in-flight barodontalgia is only minor (about one-tenth of cases). Classification
The Fédération dentaire internationale describes 4 classes of barodontalgia. The classes are based on signs and symptoms. They also provide specific and valuable recommendations for therapeutic intervention. Barotrauma
Sometimes, pressure changes damage teeth (rather than just causing pain). When the external pressure rises or falls and the trapped air within the void cannot expand or contract to balance the external pressure, the pressure difference on the rigid structure of the tooth can occasionally induce stresses sufficient to fracture the tooth or dislodge a filling. Typically this is seen in underwater divers or aviators who experience pressure changes in the course of their activity.