1. Describe the radiographic features of joint disorders seen in the
foot.
2. List the radiographic features that distinguish these joint disorders
from one another.
3. Identify the classic radiographic presentation of each joint disorder
when shown a radiographic example.
The six joint disorders most frequently seen in the foot include osteoarthritis, gouty arthritis, tarsal neuropathic arthropathy, forefoot neuropathic arthropathy, rheumatoid arthritis, and psoriatic arthritis. The following examples are "classic" presentations, in most respects. Please spend time reviewing the characteristic radiographic features of each arthritide. Be able to recognize the abnormal findings, and apply the appropriate terminology to describe them.
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| Dorsoplantar and lateral views of the first metatarsophalangeal joint. The example above demonstrates all the classic features of osteoarthritis: osteophytes (laterally and superiorly - arrow); subchondral sclerosis; nonuniform joint space narrowing laterally; geographic, subchondral decreased densities with thin sclerotic margins; and a loose osseous body (arrowhead). |
The characteristic radiographic features of osteoarthritis are:
1) joint space narrowing. The joint space narrowing typically is uneven (or, nonuniform) at the focus of the applied abnormal force or site of cartilage or subchondral bone abnormality; however, uniform narrowing may be seen if the entire cartilaginous surface is affected.
2) subchondral sclerosis (AKA eburnation). This finding is represented by periarticular increased bone density. Subchondral sclerosis is frequently found adjacent to the site of joint space narrowing. In more severe cases, it is diffuse in presentation.
3) osteophytosis. An osteophyte is a bony outgrowth (spur, exostosis) typically seen at the margin or margins of the affected joint. It may be an isolated finding, with the absence of joint space narrowing or subchondral sclerosis.
4) subchondral cyst formation. A subchondral (or, degenerative) cyst is a geographic, radiolucent lesion frequently associated with the osteoarthritic joint. It characteristically has a thin, sclerotic margin.
5) loose osseous body (AKA "joint mouse"). The loose body appears as a bone fragment or ossicle within the joint. It more than likely is related to a traumatic event, that the patient may not ever recall; it could be an osteochondral bone fragment that initiates osteoarthritis, or can represent a fractured osteophyte in an already existing osteoarthritic joint.
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Dorsoplantar view of the first metatarsophalangeal joint. A "lumpy-bumpy" increased soft tissue density and volume is seen adjacent to the first metatarsal head. Despite significant erosion of the first metatarsal head medially and laterally, the joint space is relatively spared. Note the C-shaped erosion along the lateral aspect of the hallux proximally phalanx base with the overhanging edge of bone at its margin (arrow, AKA Martel's sign). |
Characteristic radiographic features of gouty arthritis include:
1) erosion. Initial erosions are ill-defined but eventually become well-defined and frequently "C"-shaped, typically along the medial aspect of the first metatarsophalangeal and hallux interphalangeal joints.
2) overhanging margin of new bone (AKA Martel's sign). This feature is seen at the periphery of the erosion and appears to represent new bone production forming around the soft tissue tophus. When present, this finding is very characteristic of gouty arthritis.
3) normal joint space. In contrast to the inflammatory joint diseases (rheumatoid, psoriatic, and septic arthritis), the joint space is relatively spared.
4) soft tissue calcification. Small, speckled increased densities might be recognized in the soft tissue tophus. This is not a common finding.
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| Dosoplantar and lateral views of the midfoot. Note dislocation of the second metatarsal-cuneiform joint and subluxation of all remaining metatarsal-tarsal joints. Subchondral bone resorption is seen at all lesser metatarsal-tarsal and naviculocuneiform joints. Diffuse osseous sclerosis is also present throughout this region. Fragmentation can be noted along the superior aspect of the midfoot in the lateral view. |
The primary radiographic features of neuropathic osteoarthropathy at the intertarsal and metatarsal-tarsal joints include:
1) diffuse sclerosis. Increased density is seen at all affected joints and bones.
2) subchondral resorption (early). Not easily visualized due to the diffuse sclerosis, resorption at articular margins is particularly important when differentiating between early neuropathic osteoarthropathy versus osteoarthritis.
3) subluxation and dislocation. Loss of apposition eventually occurs at affected joints and progresses to gross dislocation.
4) fragmentation. Bone fragments will be seen, typically associated with the subluxation and dislocation. The fragments may be quite large in size.
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Dorsoplantar view of the forefoot. The third toe proximal phalanx base and third metatarsal head are absent. The remaining stumps are "whittled" (arthritis mutilans). The fifth toe middle and distal phalanges are also absent. no evidence of new bone production is noted. Deformity of the second metatarsal head is noted, probably the sequella of previous fracture, another complication of forefoot neuropathic arthropathy. |
The primary radiographic features of forefoot osteopathy include:
1) arthritis mutilans. Bone resorption along the medial and lateral margins of affected both is typically more pronounced than that seen in psoriatic arthritis. Phalanges and metatarsals alike can be affected, individually or en masse.
2) periostitis. Periosteal new bone production may be seen adjacent to affected joints, but is infrequently encountered.
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The above images demonstrate the classic features of rheumatoid arthritis:
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The radiographic features of rheumatoid arthritis include:
1) erosion. The outer margin of subchondral bone disappears. Initially, this may be as subtle as a "dot-dash" appearance or "skipping" along the thin white line that comprises the subchondral bone plate. Eventually, this progresses as a localized loss of marginal bone (decreased density) such that the form of the affected bone appears abnormal. Erosions typically affect the medial side of affected forefoot joints, but it additionally affects the lateral aspect of the fifth metatarsophalangeal joint. Erosion may also be seen along the posterosuperior aspect of the calcaneus in the lateral view adjacent to the retrocalcaneal bursal recess.
2) joint space narrowing. This is an early feature of an affected joint, and many times is even or uniform across the joint. However, mild subluxation can occur simultaneously, giving the appearance of uneven narrowing.
3) osteopenia. This term refers to generalized radiolucency of bones. Objective features that can be recognized include thinning of cortices, intracortical tunneling, and prominence of primary trabeculations standing out in relief. Osteopenia is a characteristic finding of rheumatoid arthritis and is associated with the other radiographic features; but, alone, osteopenia is a nonspecific finding.
4) digital malalignment and joint subluxation/dislocation. All toes (except the fifth) generally will deviate in a fibular direction relative to the metatarsals, but don't be surprised to see deviation in a tibial direction. As the disease progresses, the proximal phalangeal bases may only partially appose their respective metatarsal heads (subluxation), and can further result in dislocation (0% apposition).
5) cyst (AKA pseudocyst). Geographic, subchondral radiolucent lesions occasionally are seen centrally at affected joints.
6) ankylosis. In the later stages of rheumatoid arthritis, the joint space may disappear entirely and the two bones appear united as one. Ankylosis appears more frequently in the tarsus but can also affect the first ray. Always review additional views of the joint in question; apparent ankylosis in one view may actually be dorsal dislocation and superimposition.
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| Dorsoplantar views of the forefeet, same patient. This example demonstrates the following findings: PIPJ and DIPJ erosions, fifth toes (arrowheads); periosteal reaction, left third toe proximal phalanx (black arrow); early ivory phalanx, left hallux distal phalanx; whiskering, left hallux distal phalanx (white arrow); slight joint space narrowing, third and fourth MPJs, left foot; and spotty osteopenia, left foot. |
Characteristic radiographic features vary but include the following:
1) bone proliferation. Several forms of new bone production might be seen with psoriatic arthritis, including whiskering, "ivory phalanx", and periostitis. Whiskering and the ivory phalanx typically affect the hallux distal phalanx; whiskering appears as small spicules of bone arising perpendicular from the phalanx shaft, and ivory phalanx refers to overall increased density of the phalanx. Periosteal new bone production is seen adjacent to affected metatarsophalangeal joints.
2) erosion. Loss of the marginal subchondral bone plate may appear no different than that seen in rheumatoid arthritis. However, in contrast to rheumatoid arthritis, erosions frequently affect the medial and lateral margins of the metatarsophalangeal and hallux interphalangeal joints. Erosion can also occurs centrally within the joint, and be quite destructive visually, leading to joint space widening of interphalangeal joints or arthritis mutilans of metatarsophalangeal joints (see below).
3) arthritis mutilans. Excessive bone erosion along both the medial and lateral margins of a metatarsophalangeal joint can result in an appearance that has frequently been described by the following figurative terminology: pencil-in-cup deformity, mortar-in-pestle, sucked candy, and whittling. This gross, erosive deformity mutilates the joint, thus the term arthritis mutilans.
4) joint space widening. Central joint erosion especially affects the interphalangeal joints and results in a relative widening of the joint space.
5) joint space narrowing. Narrowing of joint spaces is more frequently seen early is the disease at the metatarsophalangeal joints.
© Copyright 1998, Robert A. Christman, D.P.M.
These articles and figures may not be published, reposted, or redistributed without permission from Dr. Christman.
This page was updated May 5, 1998.
