Diagnostic Assessment — Left Knee - Intercruciate Ganglion
Example 1 of 1 · fictitious patient (Veteran BF)
Diagnostic Assessment
Left Knee - Intercruciate Ganglion
BOP Code: 8 of 2025 (Ganglion)
RH Code: 7 of 2025 (Ganglion)
ADF History
Veteran BF, date of birth 17 May 1990, Royal Australian Air Force, Airfield Defence Guard, enlisted 22 February 2009, medically discharged 30 June 2021. Operational service: Middle East Area of Operations, 10 January 2017 to 28 July 2017 (warlike); Middle East Area of Operations, 05 February 2019 to 20 August 2019 (warlike).
Occupational History
As an airfield defence guard the veteran conducted ground defence of air bases, including foot and vehicle patrols carrying 25 to 35 kilograms of body armour, weapon and equipment, sentry duty at fixed positions, quick reaction responses and live-fire training. The role involves repeated kneeling, squatting and prone firing positions, running in equipment, and mounting and dismounting from protected mobility vehicles, often at night.
These duties carry a high risk of acute knee injury from falls, twisting and direct impact, and of cumulative loading of the knee joint from load carriage and kneeling. Members are frequently posted to remote bases and deployed locations where specialist orthopaedic and imaging services are not readily available.
History
Veteran BF, an airfield defence guard in the Royal Australian Air Force, injured her left knee in a 1.5-metre fall from a protected mobility vehicle on warlike service in the Middle East on 14 March 2017. She developed an intercruciate ganglion of the anterior cruciate ligament in September 2017, which enlarged and caused locking after planned surgery could not be obtained before and during her second deployment in 2019.
Timeline
- 24 Oct 2016 — At her pre-deployment health assessment the veteran had no knee symptoms, full range of motion of both knees and no history of knee injury. She was assessed as fit for deployment with no restrictions. "knees NAD, fit to deploy"
- 14 Mar 2017 — During warlike service in the Middle East the veteran fell about 1.5 metres from the rear step of a protected mobility vehicle during a night-time base defence response, landing on her flexed left knee on concrete while carrying about 32 kilograms. The role 2 medical officer recorded a tense effusion, posterior knee tenderness, pain at end-range flexion and inability to weight bear. Plain radiographs showed no fracture. She was placed on light duties for three weeks. "fall 1.5 m, L knee effusion"
- 02 Aug 2017 — At her post-deployment health assessment the veteran reported intermittent aching behind the left knee after patrols, which settled with rest. Range of motion was full and there was no effusion. She was advised to report any increase in symptoms. "intermittent posterior knee ache"
- 25 Sep 2017 — The veteran presented to the base health centre with five days of constant deep pain behind the left knee, worse with squatting, kneeling and full extension, and night pain. Examination showed pain at the extremes of flexion and extension, a 5-degree loss of terminal extension and a stable knee on ligament testing. A sports physician referral and MRI were requested. "posterior knee pain, terminal extension painful"
- 30 Oct 2017 — MRI of the left knee showed a 22 x 9 mm multiloculated cystic lesion within the intercondylar notch along the anterior cruciate ligament, consistent with an intercruciate ganglion, with an intact ligament and no meniscal tear. On 06 November 2017 a sports physician confirmed the diagnosis and requested physiotherapy and urgent orthopaedic review. "intercruciate ganglion, ACL intact"
- 12 Oct 2018 — After a referral delay of more than nine months while the veteran was posted to an RAAF base in northern Australia without physiotherapy or orthopaedic services, an orthopaedic surgeon reviewed her. Pain and loss of terminal extension had persisted. He recommended arthroscopic decompression of the ganglion and listed her for surgery in March 2019. "listed arthroscopic decompression"
- 18 Sep 2019 — Four weeks after returning from her second warlike deployment, during which her surgery was cancelled and could not be obtained, the veteran reported locking of the knee in extension from June 2019 and constant pain. Repeat MRI showed the ganglion had enlarged to 38 x 14 mm with extension into the posterior notch. Extension was limited by 10 degrees. "ganglion enlarged 38 mm, locking"
- 21 Nov 2019 — The orthopaedic surgeon performed arthroscopic decompression and debridement of the intercruciate ganglion. Operative findings confirmed a mucinous cyst arising from the anterior cruciate ligament, and histology showed a fibrous-walled cyst without an epithelial lining. She was medically downgraded and later discharged. "arthroscopic decompression, histology confirmed"
Symptoms
At onset the veteran had constant deep pain behind the left knee, worse with squatting, kneeling, running and full extension, with night pain and stiffness and a small loss of terminal extension. Before surgery the pain became constant, and from June 2019 the knee locked in extension, with a 10-degree loss of extension and difficulty with stairs and load carriage.
She now reports residual posterior knee pain after prolonged standing, kneeling or walking more than 3 kilometres, intermittent swelling and stiffness, and inability to run or kneel for long. She has not returned to load carriage or field activity.
Imaging
- 14 Mar 2017 — Left knee radiographs, role 2 facility: "No fracture or dislocation. Moderate joint effusion."
- 30 Oct 2017 — MRI left knee: "22 x 9 mm multiloculated fluid-signal lesion in the intercondylar notch, interposed between the fibres of the anterior cruciate ligament, consistent with an intercruciate (ACL) ganglion. Anterior cruciate ligament fibres intact. Menisci and articular cartilage normal."
- 18 Sep 2019 — MRI left knee: "Interval enlargement of the intercruciate ganglion to 38 x 14 mm, extending into the posterior intercondylar notch towards the posterior cruciate ligament, with surrounding bone marrow oedema at the femoral attachment of the anterior cruciate ligament."
Onset Date
The most likely date of onset of this condition is 20 Sep 2017.
At that date the veteran was serving full time as an airfield defence guard at an RAAF base in Australia, having returned from warlike service in the Middle East on 28 July 2017. Her duties included patrols with load carriage and repeated kneeling at firing positions. On that date her intermittent posterior knee ache became constant, with pain at end-range flexion and extension.
This date is appropriate because her post-deployment health assessment of 02 August 2017 recorded full range of motion with no effusion and only intermittent aching after patrols, and she first presented with constant posterior knee pain and loss of terminal extension on 25 September 2017, five days after this date. MRI on 30 October 2017 confirmed the ganglion. The date falls within uninterrupted full-time service.
For the acute trauma factor, the 1 year before clinical onset runs from 20 Sep 2016 to 20 Sep 2017. The fall onto the left knee on 14 Mar 2017, on warlike service in the Middle East, occurred 6 months and 6 days before onset, within that window.
For the worsening factors, the documented clinical worsening is the MRI of 18 Sep 2019, which showed enlargement of the ganglion from 22 x 9 mm to 38 x 14 mm, with locking from June 2019. Before that worsening, the orthopaedic referral was not actioned from 06 Nov 2017 to 22 Aug 2018 during peacetime service, and the planned surgery could not be obtained during her warlike deployment from 05 Feb 2019 to 20 Aug 2019.
1. What is the formal diagnosis of the condition claimed above?
The formal diagnosis is Left Knee - Intercruciate Ganglion (ICD-10-AM M67.46), a ganglion of the anterior cruciate ligament, under the Statements of Principles concerning ganglion, Balance of Probabilities No. 8 of 2025 and Reasonable Hypothesis No. 7 of 2025.
A ganglion is a benign cystic lesion overlying a joint or tendon, with a thin fibrous capsule and no epithelial lining, filled with clear mucinous fluid. An intercruciate ganglion arises within the intercondylar notch of the knee from the cruciate ligaments, most often the anterior cruciate ligament, and is thought to result from mucoid degeneration of connective tissue after trauma. It causes deep posterior knee pain, pain at the extremes of flexion and extension, and, as it enlarges, a block to full extension or locking. Treatment is by image-guided aspiration or arthroscopic decompression.
The condition followed a fall onto the flexed left knee on warlike service on 14 March 2017. It began on 20 September 2017, was confirmed on MRI on 30 October 2017 and worsened by September 2019 while surgery could not be obtained.
2. For each diagnosis identified, please also provide the following dates:
When did the veteran first experience symptoms attributable to this condition?
20 September 2017.
When did the veteran first present to a health / medical provider for this condition?
25 September 2017.
When was the condition confirmed / formally diagnosed?
30 October 2017.
When did the veteran first present to you (or your practice) for this condition?
03 February 2025.
3. How was this diagnosis confirmed? i.e. what were the key symptoms and signs, investigation results, specialist opinions?
The diagnosis was confirmed on MRI on 30 October 2017, which showed a 22 x 9 mm multiloculated fluid-signal cystic lesion within the intercondylar notch, interposed between the fibres of an intact anterior cruciate ligament. This meets the Statement of Principles definition of ganglion: a benign cystic lesion overlying a joint or tendon, accompanied by pain and loss of function. It is not a bursal, synovial, epidermoid or Tarlov cyst.
The clinical picture was consistent, with deep posterior knee pain and pain at the extremes of motion. At arthroscopy on 21 November 2019 a mucinous cyst arising from the anterior cruciate ligament was found, and histology confirmed a fibrous-walled cyst without an epithelial lining.
4. What do you consider to be the cause(s) of the condition in this veteran? Give consideration to constitutional and common risk factors, pre-existing injuries or diseases, and occupational or lifestyle risks, as well as direct causative mechanisms.
Legislation: the clinical onset of this condition was on 20 September 2017, after 1 July 2004, during continuous full-time service. This is a Military Rehabilitation and Compensation Act 2004 (MRCA) claim and the Statements of Principles apply. The Balance of Probabilities instrument applies to peacetime service, and its single factor, the inability to obtain appropriate clinical management, applies to the aggravation of a ganglion that was contracted during but did not arise out of peacetime service. The Reasonable Hypothesis instrument applies to the veteran's warlike service in the Middle East in 2017, where the knee injury occurred, and in 2019, where the planned surgery could not be obtained.
Each factor must be related to the person's relevant service. Under the beneficial approach required by the legislation, the absence of documentation does not mean that an event or exposure did not occur: lack of evidence is not evidence of lack.
Balance of Probabilities — Statement of Principles concerning Ganglion, No. 8 of 2025
Causative factors
Worsening factors
Factor 9(1): inability to obtain appropriate clinical management for ganglion before clinical worsening. — MET
- The left knee ganglion was first diagnosed on MRI on 30 October 2017 and arose from the deployment injury of 14 March 2017, so for the purposes of peacetime service it was contracted during, but did not arise out of, that service, as section 10(2) requires. After diagnosis the treating sports physician requested physiotherapy and urgent orthopaedic review on 06 November 2017. The veteran was then posted to an RAAF base in northern Australia that had no on-base physiotherapist and no visiting orthopaedic surgeon, and the referral was not actioned by the base health centre until 22 August 2018, a delay of more than nine months. When the orthopaedic surgeon saw her on 12 October 2018 he recommended arthroscopic decompression and listed her for surgery in March 2019. During this period she continued to perform airfield defence duties, including patrols carrying 30 kilograms and repeated kneeling and squatting at firing positions, which loaded the knee. The untreated ganglion enlarged from 22 x 9 mm to 38 x 14 mm and began to block knee extension, as shown on MRI on 18 September 2019. Under Brew v Repatriation Commission (1999) the administrative failure to action a specialist referral for nine months, and the absence of local services, amount to an inability to obtain appropriate clinical management before the clinical worsening.
Reasonable Hypothesis — Statement of Principles concerning Ganglion, No. 7 of 2025
Causative factors
Factor 9(1): having acute trauma due to a significant physical force applied to the affected joint or tendon within the 1 year before clinical onset; — MET
- On 14 March 2017, during warlike service in the Middle East Area of Operations, the veteran was dismounting from the rear of a protected mobility vehicle at night during a base defence response when the step gave way. Carrying about 32 kilograms of body armour, weapon and equipment, she fell about 1.5 metres and landed on her flexed left knee on concrete, with the knee forced into hyperflexion and twisting. A significant physical force was applied directly to the affected joint. The role 2 medical officer recorded an immediate tense effusion, inability to weight bear for two days, tenderness at the back of the knee and pain at the end of flexion, and plain radiographs showed no fracture. MRI was not available in theatre. Posterior knee pain persisted intermittently, and on 20 September 2017 she developed constant deep posterior knee pain with painful limitation of full flexion and extension. MRI on 30 October 2017 confirmed an intercruciate ganglion arising from the anterior cruciate ligament. The onset on 20 September 2017 was 6 months and 6 days after the injury, within the 1 year before clinical onset, which runs from 20 September 2016 to 20 September 2017. Trauma to the cruciate ligaments is the recognised mechanism for intercruciate ganglion formation through mucoid degeneration of the injured ligament.
Worsening factors
Factor 9(2): inability to obtain appropriate clinical management for ganglion before clinical worsening. — MET
- After the diagnosis in October 2017 the veteran was listed for arthroscopic decompression of the ganglion in March 2019, but the surgery was cancelled when she was deployed again on warlike service to the Middle East Area of Operations from 05 February 2019 to 20 August 2019. No surgical, imaging or physiotherapy services for the knee were available at her deployed location, and a request for an early return for surgery was declined on operational grounds in May 2019. Throughout the deployment she carried loads of 30 to 35 kilograms on base patrols and spent long periods kneeling at sentry positions. The knee developed episodes of locking in extension from June 2019. MRI on 18 September 2019, four weeks after her return, showed the ganglion had enlarged from 22 x 9 mm to 38 x 14 mm, extending into the posterior intercondylar notch, with a 10-degree loss of extension. The inability to obtain the planned surgery on operational service occurred before this documented clinical worsening and materially contributed to it. Under Brew v Repatriation Commission (1999) operational constraints that prevent prescribed treatment amount to an inability to obtain appropriate clinical management.
The % contribution of the causes is 100% and significant.
Sequelae
The intercruciate ganglion is a sequela of the left knee injury sustained on warlike service on 14 March 2017. The loss of extension, locking and residual posterior knee pain, and the arthroscopic surgery required to treat them, are sequelae of the ganglion.
Unintended Consequence
Not met on the records reviewed. The ganglion was not caused by medical treatment provided by the Commonwealth; its enlargement followed the failure to provide treatment, which is addressed under the inability factor.
Inability to Attain Appropriate Medical Management
MET. After diagnosis in October 2017 the veteran's urgent orthopaedic referral was not actioned for more than nine months because her base had no physiotherapy or orthopaedic services, and her scheduled arthroscopic decompression was then cancelled when she deployed on warlike service in February 2019, with a request to return early for surgery declined on operational grounds. The ganglion enlarged from 22 mm to 38 mm and caused locking before she could be treated. Applying the objective and subjective tests in Brew v Repatriation Commission (Full Federal Court, 10 September 1999, Merkel J), administrative delay and operational constraints that prevent prescribed treatment amount to an inability to obtain appropriate clinical management.
5. Please provide a Health Summary and a medication / prescribing history.
See attached report.
References
- 24 Oct 2016, Pre-deployment health assessment, Medical Officer
- 14 Mar 2017, Role 2 treatment record and radiographs, Medical Officer, Middle East Area of Operations
- 02 Aug 2017, Post-deployment health assessment, Medical Officer
- 25 Sep 2017, Outpatient health record, Medical Officer, Base health centre
- 30 Oct 2017, MRI left knee report, Radiologist
- 06 Nov 2017, Specialist consultation, Sports physician
- 12 Oct 2018, Orthopaedic consultation, Orthopaedic surgeon
- 18 Sep 2019, MRI left knee report, Radiologist
- 21 Nov 2019, Operation report and histopathology, Orthopaedic surgeon and pathologist
- Statement of Principles concerning Ganglion (Balance of Probabilities) No. 8 of 2025, Repatriation Medical Authority
- Statement of Principles concerning Ganglion (Reasonable Hypothesis) No. 7 of 2025, Repatriation Medical Authority
