# Pittsburgh knee rule (Seaberg 1994)

Pittsburgh knee

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/pittsburgh_knee`
HTML: https://magentlab.com/docs/pittsburgh-knee
Markdown: https://magentlab.com/docs/pittsburgh-knee.md

Not a medical device. Not a diagnosis, dose, or listing recommendation.

## What it computes

Apply the Seaberg 1994 Pittsburgh knee rule: a knee radiograph is indicated after fall or blunt trauma if the patient cannot walk four weight-bearing steps or is younger than 12 or older than 50.

## When to use

When an agent needs the published Pittsburgh knee radiography rule and must not apply the Ottawa knee rule or invent a different age cutoff.

## When not to use

- Not a diagnosis of fracture. magent does not examine the knee.
- Without fall or blunt trauma the rule does not indicate a film.
- Age 12 and age 50 do not meet the age limb (younger than 12 or older than 50). This is not the Ottawa knee rule (Stiell 1995).

## Formula

```
Knee x-ray indicated iff blunt_trauma_or_fall and (unable_to_walk_four_steps or age < 12 or age > 50)
```

## Citation

[Clinical decision rule for knee radiographs](https://doi.org/10.1016/0735-6757(94)90274-7)
Seaberg DC, Jackson R
Am J Emerg Med. 1994;12(5):541-543
DOI: [10.1016/0735-6757(94)90274-7](https://doi.org/10.1016/0735-6757(94)90274-7)

## Worked example

### Age 30, blunt trauma, can walk four steps

Given: `age=30, blunt_trauma_or_fall=true, unable_to_walk_four_steps=false`

1. mechanism true; unable false; age 30 is not <12 and not >50
2. x-ray not indicated


### Age 30, blunt trauma, unable to walk four steps

Given: `age=30, blunt_trauma_or_fall=true, unable_to_walk_four_steps=true`

1. mechanism and inability to ambulate → x-ray indicated


## Also searched as

- Pittsburgh knee rules
- Pittsburgh knee rule
- Seaberg knee
- knee radiograph rule
- blunt trauma knee x-ray
- Pittsburgh vs Ottawa knee

## Parameters

- `age` (integer, required): Age in years (0-120). Seaberg 1994: younger than 12 or older than 50 meets the age limb; 12 and 50 do not.
- `blunt_trauma_or_fall` (boolean, required): Fall or blunt trauma mechanism (Seaberg 1994). true or false as assigned by the caller. The rule does not indicate a film without this mechanism.
- `unable_to_walk_four_steps` (boolean, required): Inability to ambulate four weight-bearing steps (Seaberg 1994). true or false as assigned by the caller.

## Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

Method: `POST /api/calc/pittsburgh_knee`
Max items: 25
Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic)
Status: PREVIEW

- 1 to 25 items. Each item uses the same keys as the GET query parameters.
- POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
- The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
- HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
- Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
- x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request:

```json
{
  "items": [
    {
      "age": "30",
      "blunt_trauma_or_fall": "true",
      "unable_to_walk_four_steps": "false"
    },
    {
      "age": "30",
      "blunt_trauma_or_fall": "true",
      "unable_to_walk_four_steps": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/pittsburgh-knee

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/pittsburgh_knee",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Seaberg DC, Jackson R",
        "doi": "10.1016/0735-6757(94)90274-7",
        "id": "seaberg-1994",
        "source": "Am J Emerg Med. 1994;12(5):541-543",
        "title": "Clinical decision rule for knee radiographs"
      },
      "formula": "pittsburgh_knee",
      "formula_expression": "Knee x-ray indicated iff blunt_trauma_or_fall and (unable_to_walk_four_steps or age < 12 or age > 50)",
      "age_years": 30,
      "criteria": [
        {
          "factor": "blunt_trauma_or_fall",
          "met": true
        },
        {
          "factor": "unable_to_walk_four_steps",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_lt_12",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_gt_50",
          "met": false
        }
      ],
      "xray_indicated": false,
      "blunt_trauma_or_fall": true,
      "unable_to_walk_four_steps": false
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Seaberg DC, Jackson R",
        "doi": "10.1016/0735-6757(94)90274-7",
        "id": "seaberg-1994",
        "source": "Am J Emerg Med. 1994;12(5):541-543",
        "title": "Clinical decision rule for knee radiographs"
      },
      "formula": "pittsburgh_knee",
      "formula_expression": "Knee x-ray indicated iff blunt_trauma_or_fall and (unable_to_walk_four_steps or age < 12 or age > 50)",
      "age_years": 30,
      "criteria": [
        {
          "factor": "blunt_trauma_or_fall",
          "met": true
        },
        {
          "factor": "unable_to_walk_four_steps",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_lt_12",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_gt_50",
          "met": false
        }
      ],
      "xray_indicated": false,
      "blunt_trauma_or_fall": true,
      "unable_to_walk_four_steps": false
    }
  ]
}
```

## Response fields

- `formula` (string): pittsburgh_knee
- `formula_expression` (string): Seaberg 1994 rule
- `xray_indicated` (boolean): Whether the rule indicates a knee series
- `age_years` (integer): Caller age
- `blunt_trauma_or_fall` (boolean): Mechanism limb
- `unable_to_walk_four_steps` (boolean): Ambulation limb
- `criteria` (array): Evaluated criteria
- `citation` (object): Seaberg 1994
- `disclaimer` (string): Not a medical device

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Seaberg DC, Jackson R",
    "doi": "10.1016/0735-6757(94)90274-7",
    "id": "seaberg-1994",
    "source": "Am J Emerg Med. 1994;12(5):541-543",
    "title": "Clinical decision rule for knee radiographs"
  },
  "formula": "pittsburgh_knee",
  "formula_expression": "Knee x-ray indicated iff blunt_trauma_or_fall and (unable_to_walk_four_steps or age < 12 or age > 50)",
  "age_years": 30,
  "criteria": [
    {
      "factor": "blunt_trauma_or_fall",
      "met": true
    },
    {
      "factor": "unable_to_walk_four_steps",
      "met": false
    },
    {
      "value": 30,
      "factor": "age_lt_12",
      "met": false
    },
    {
      "value": 30,
      "factor": "age_gt_50",
      "met": false
    }
  ],
  "xray_indicated": false,
  "blunt_trauma_or_fall": true,
  "unable_to_walk_four_steps": false
}
```

## Errors

- HTTP 400 `invalid_pittsburgh_age`: age must be an integer from 0 to 120 (Seaberg 1994 includes children). Returned before settlement; you are not charged.
- HTTP 400 `invalid_flag`: boolean clinical flags must be true or false Returned before settlement; you are not charged.
- HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
- HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
- HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged.

Shared HTTP 402 and 503: https://magentlab.com/docs/payments

## Related tools

- [Ottawa knee rule](https://magentlab.com/docs/ottawa-knee) — Apply the Stiell 1995 Ottawa knee rule and return whether a knee x-ray series is indicated from age and caller-assigned bone tenderness, flexion, and weight-bearing findings.
- [Ottawa ankle rule](https://magentlab.com/docs/ottawa-ankle) — Apply the Stiell 1992 Ottawa ankle rule and return whether an ankle x-ray series is indicated from caller-assigned malleolar pain, malleolar bone tenderness, and inability to bear weight.

## Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s.

- GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall).
- HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote.
- Sign accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON echoing accepted, payload, and extensions when present).
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact nonce only after a new HTTP 402.

- offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront.
- offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization.

- not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search.

Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers).

Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments

Stdio MCP (one process per host): https://magentlab.com/docs/mcp

## Guarantees

- HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged.
- exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
- HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
- Execution is timeout-bounded and concurrency-capped.
- Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.