Joint | Semiquantitative scoring system, BM |

Anterior elbow | 0: No or minimal synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion2: Moderate synovial hypertrophy/effusion up to, but not beyond the imaginary line*3: Severe synovial hypertrophy/effusion beyond the imaginary line* and a clearly convex shape* The line above the radial fossa; between the proximal end of the fossa to the top of the cartilage over the capitulum humeri |

Posterior elbow | 0: No or minimal synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion, filling up to 25% of the fossa2: Moderate synovial hypertrophy/effusion filling up to 50% of the fossa, but not beyond the imaginary line*3: Severe synovial hypertrophy/effusion filling more than 50% of the fossa and/or extending beyond the imaginary line** The line above the fossa olecrani; between the proximal end of the fossa to the top of the cartilage of the trochlea humeri |

Radiocarpal and midcarpal | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion2: Moderate synovial hypertrophy/effusion up to, but not beyond the imaginary line*3: Severe synovial hypertrophy/effusion with a convex shape extending beyond the imaginary line* and can push up the extensor tendons* The line between the top of the cartilage of the distal end of the radius to the top of the cartilage of the capitate (just proximal to the CMC joint) |

MCP2–3, dorsal | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion but not beyond the imaginary line*2: Moderate synovial hypertrophy/effusion extending beyond the imaginary line*, but without overall convex shape3: Severe synovial hypertrophy/effusion extending beyond the imaginary line* with a clearly convex shape* The line between the top of the cartilage of the distal end of the metacarpal to the top of the cartilage of the proximal end of the phalanx |

PIP2–3, dorsal | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion but not beyond the imaginary line*2: Moderate synovial hypertrophy/effusion extending beyond the imaginary line*, but without overall convex shape3: Severe synovial hypertrophy/effusion extending beyond the imaginary line* with a clearly convex shape*The line between the top of the cartilage of the distal end of the proximal phalanx to the top of the cartilage of the proximal end of the middle phalanx |

PIP2–3, volar | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion, possible to extend proximally but without convex shape2: Moderate synovial hypertrophy/effusion extending over the proximal phalanx with convex shape, but not filling the joint space between proximal and middle phalanx3: Severe synovial hypertrophy/effusion extending over the proximal phalanx and filling the joint space between proximal and middle phalanx with an overall convex shape |

Hip | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion, but just a ‘slit’ of fluid between the two layers of the capsule2: Moderate synovial hypertrophy/effusion leading to a straight line/minimal convex shape of the capsule3: Severe synovial hypertrophy/effusion with a clearly convex shape, the effusion can also extend proximally over the femoral head |

Knee, suprapatellar recess | 0: ‘Slit’ of fluid/synovium without elevation of the prepatellar fat pad but with only minimal extension beyond the prepatellar fat pad1: Mild synovial hypertrophy/effusion with elevation of the prepatellar fat pad and extension proximally <50% of the visualised portion of the quadriceps tendon2: Moderate synovial hypertrophy/effusion elevating the prepatellar fat pad with extension proximally >50% of the visualised portion of the quadriceps tendon3: Significant distension of the suprapatellar recess throughout the image, and with the most proximal portion of the synovial recess being >50% of the maximum distension of the recess17 |

Knee, lateral parapatellar recess | 0: Empty parapatellar recess but a minimal bulge of synovial hypertrophy/effusion may be found extending to the patellofemoral joint line1: Synovial hypertrophy/effusion filling <1/3 of the full area of the parapatellar recess2: Synovial hypertrophy/effusion filing between 1/3 to 2/3 of the full area of the parapatellar recess3: Synovial hypertrophy/effusion that fills >2/3 of the full area of the parapatellar recess and clearly pushing up the retinaculum17 |

Tibiotalar | 0: No sign of synovial hypertrophy/effusion in the tibiotalar joint, but possible to have a minimal amount of fluid in the concave neck of the talus1: Mild synovial hypertrophy/effusion filling the gap between the tibia and the talus and in the concave neck of the talus, but not continuously over the talus2: Moderate synovial hypertrophy/effusion filling <50% of the area between the tibia, the talus and the imaginary line* and continuously over the talus3: Severe synovial hypertrophy/effusion filling >50% of the area between the tibia, the talus and the imaginary line* or beyond the imaginary line** The line between the top of the cartilage of the distal end of the tibia and the top of the cartilage of the talar head |

Talonavicular | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion but not beyond the imaginary line*2: Moderate synovial hypertrophy/effusion extending beyond the imaginary line* and proximal with a concave or straight shape3: Severe synovial hypertrophy/effusion extending beyond the imaginary line* and over the talus with a convex shape clearly pushing up the joint capsule* The line between the top of the cartilage of the head of the talus to the top of the cartilage of the navicular bone |

Anterior subtalar | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion covering up to 25% of the straight part of the talus2: Moderate synovial hypertrophy/effusion covering up to 50% of the straight part of the talus3: Severe synovial hypertrophy/effusion covering more than 50% of the straight part of the talus |

Posterior subtalar | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion filling the gap between the talus and the calcaneus2: Moderate synovial hypertrophy/effusion extending beyond the talus and the calcaneus but not with a convex shape3: Severe synovial hypertrophy/effusion extending beyond the talus and the calcaneus with a convex shape |

MTP2–3 dorsal | 0: No sign of synovial hypertrophy/effusion1: Mild synovial hypertrophy/effusion but not beyond the imaginary line*2: Moderate synovial hypertrophy/effusion extending beyond the imaginary line*, but without overall convex shape3: Severe synovial hypertrophy/effusion extending beyond the imaginary line* with a clearly convex shape* The line between the top of the cartilage of the distal end of the metatarsal to the top of the cartilage of the proximal end of the phalanx |

BM, B-mode; CMC, carpometacarpal; MCP, metacarpophalangeal; MTP, metatarsophalangeal; PIP, proximal interphalangeal.