# Kocher Score for Septic Arthritis vs Transient Synovitis (Pediatric Hip)

> Kocher Score for Septic Arthritis vs Transient Synovitis (Pediatric Hip) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Computes the Kocher 1999 four-predictor clinical decision score for differentiating septic arthritis from transient synovitis in children with irritable hip, returning the published predicted probability of septic arthritis.

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/kocher
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/kocher-score-for-septic-arthritis-vs-transient-synovitis-pediatric-hip-2b496c9b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qwgD9Ly2Wm-mfY0x9QbS9

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability kocher-score-for-septic-arthritis-vs-transient-synovitis-pediatric-hip-2b496c9b
```

Example prompt: My 7-year-old patient has an irritable hip — they have a history of fever over 38.5°C, are non-weight-bearing, ESR is 52 mm/h, and WBC is 14,200/µL. What's the Kocher score and predicted probability of septic arthritis?

## When to prefer this

Use this endpoint when you need the original Kocher 1999 four-predictor score specifically — not the Caird et al. CRP-extended version. It is appropriate only for pediatric patients with irritable hip being evaluated for septic arthritis versus transient synovitis. Prefer this over manual lookup when integrating clinical decision support into an agentic workflow, EHR assistant, or medical education tool. Do not use for adults or as a substitute for clinical judgment or aspiration.

## Known failure modes

- Missing required parameters (history_of_fever, non_weight_bearing, esr_mm_h) returns a validation error
- ESR value outside valid range (1.0–150.0 mm/h) may be rejected
- WBC value outside valid range returns error
- Providing both wbc_ul and wbc_k_ul may cause ambiguity; only one should be provided
- Payment not included or insufficient USDC results in 402 Payment Required
- Score is inapplicable to adults or to the Caird CRP-modified criteria — misuse yields a valid but clinically inappropriate result

## How this service works

Kocher 1999 four predictors for children with irritable hip: history of fever (oral temperature >38.5 C), non-weight-bearing, ESR >=40 mm/h, and serum WBC >12000/uL; 1 point each, max 4. Returns published predicted probability of septic arthritis vs transient synovitis. Deterministic published score with citation; not a diagnosis, not Caird CRP, not adults, and not an aspiration order.

## Output

Returns the computed Kocher score (integer 0–4), the published predicted probability of septic arthritis corresponding to that score (from Kocher 1999), and a citation. The result is a deterministic lookup of published data — not a diagnosis, not the Caird CRP-extended score, not applicable to adults, and does not constitute an aspiration order.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "history_of_fever",
      "non_weight_bearing",
      "esr_mm_h"
     ],
     "properties": {
      "wbc_ul": {
       "type": "number",
       "description": "WBC in cells/µL (same as cells/mm^3). Provide wbc_k_ul or wbc_ul. Range 10-500000. >12000 scores 1 (12000 does not; 12001 does)."
      },
      "esr_mm_h": {
       "type": "number",
       "description": "Erythrocyte sedimentation rate in mm/h (1.0-150.0). ≥40 scores 1 (40 scores; 39.9 does not)."
      },
      "wbc_k_ul": {
       "type": "number",
       "description": "WBC in 10^3/µL (same as 10^9/L). Provide wbc_k_ul or wbc_ul. Range 0.01-500. >12000/µL scores 1."
      },
      "history_of_fever": {
       "type": "boolean",
       "description": "History of fever (oral temperature >38.5°C in Kocher 1999). true or false as assigned by the caller."
      },
      "non_weight_bearing": {
       "type": "boolean",
       "description": "Non-weight-bearing on the affected limb (Kocher 1999). true or false as assigned by the caller."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "path": "/api/calc/kocher",
  "count": 2,
  "items": [
   {
    "score": 0,
    "wbc_ul": 8000,
    "formula": "kocher",
    "citation": {
     "id": "kocher-1999",
     "doi": "10.2106/00004623-199912000-00002",
     "pmid": "10608376",
     "title": "Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm",
     "source": "J Bone Joint Surg Am. 1999;81(12):1662-1670",
     "authors": "Kocher MS, Zurakowski D, Kasser JR"
    },
    "esr_mm_h": 20,
    "max_score": 4,
    "components": [
     {
      "factor": "history_of_fever",
      "points": 0,
      "present": false
     },
     {
      "factor": "non_weight_bearing",
      "points": 0,
      "present": false
     },
     {
      "value": 20,
      "factor": "esr_ge_40",
      "points": 0,
      "present": false
     },
     {
      "value": 8000,
      "factor": "wbc_gt_12000",
      "points": 0,
      "present": 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.",
    "formula_expression": "Kocher = history_of_fever + non_weight_bearing + (esr_mm_h >= 40) + (wbc_ul > 12000); each 1; max 4; predicted probability 0:<0.2% 1:3.0% 2:40.0% 3:93.1% 4:99.6%",
    "predicted_probability": "<0.2%"
   },
   {
    "score": 0,
    "wbc_ul": 8000,
    "formula": "kocher",
    "citation": {
     "id": "kocher-1999",
     "doi": "10.2106/00004623-199912000-00002",
     "pmid": "10608376",
     "title": "Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm",
     "source": "J Bone Joint Surg Am. 1999;81(12):1662-1670",
     "authors": "Kocher MS, Zurakowski D, Kasser JR"
    },
    "esr_mm_h": 20,
    "max_score": 4,
    "components": [
     {
      "factor": "history_of_fever",
      "points": 0,
      "present": false
     },
     {
      "factor": "non_weight_bearing",
      "points": 0,
      "present": false
     },
     {
      "value": 20,
      "factor": "esr_ge_40",
      "points": 0,
      "present": false
     },
     {
      "value": 8000,
      "factor": "wbc_gt_12000",
      "points": 0,
      "present": false
     }
    ],
    "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous a
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/kocher-score-for-septic-arthritis-vs-transient-synovitis-pediatric-hip-2b496c9b/health.json
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