Right Knee - Popliteal Cyst — DVA claim example

Diagnostic Assessment — Right Knee - Popliteal Cyst

Example 1 of 1 · fictitious patient (Veteran DY)

Diagnostic Assessment

Right Knee - Popliteal Cyst

BOP Code: 32 of 2018 (Popliteal Cyst)
RH Code: 31 of 2018 (Popliteal Cyst)

ADF History

Veteran DY, date of birth 19 May 1982, Australian Army, Rifleman (Infantry), re-mustered to Supply Operator in 2014, enlisted 15 January 2001, medically discharged 30 September 2020. Operational service: Afghanistan, 01 September 2006 to 15 April 2007 (warlike); Middle East Area of Operations (Iraq), 10 January 2018 to 25 July 2018 (warlike).

Occupational History

Infantry soldiers patrol over rough ground carrying 30 to 45 kilograms, kneel and squat for long periods, and repeatedly jump down from vehicles, walls and ditches under load. These activities apply twisting and compressive forces to the knee and cause meniscal tears, ligament injuries and, over time, post-traumatic osteoarthritis. Infantry soldiers with knee injuries are commonly re-mustered to less physically demanding trades.

Supply operators receive, store and issue stores and equipment. The work involves repeated lifting and carrying of boxes and equipment of 10 to 25 kilograms, loading and unloading trucks and pallets by hand, climbing on and off vehicle trays, squatting and kneeling in warehouses, and long periods of standing. On deployment these tasks are performed in extreme heat at a high tempo, with limited access to orthopaedic care, imaging and procedures such as joint aspiration.

History

Veteran DY, an infantry soldier and later supply operator in the Australian Army, tore the medial meniscus of his right knee during warlike service in Afghanistan in 2006, developed post-traumatic osteoarthritis and had a medial unicompartmental knee replacement in 2014. A right popliteal cyst began on 05 August 2016 with osteoarthritic synovitis of the knee, and it worsened and ruptured on 14 June 2018 while he was unloading stores during warlike service in Iraq, shortly after a lateral meniscal tear.

Timeline

• 14 Dec 2006 — During warlike service in Afghanistan the veteran twisted his right knee jumping down from a vehicle carrying about 35 kg. He had immediate medial knee pain, a large effusion within hours and a locked knee. The medical officer recorded medial joint line tenderness, a positive McMurray test and a 20 degree loss of extension. He was evacuated to the role 3 hospital, where an acute bucket-handle tear of the medial meniscus was diagnosed. "R knee locked, medial meniscal tear"
• 10 May 2007 — After return to Australia an orthopaedic surgeon performed arthroscopic partial medial meniscectomy of the right knee, removing about 60 per cent of the medial meniscus. Early chondral softening of the medial femoral condyle was noted. He returned to infantry duties after four months. "arthroscopic partial medial meniscectomy"
• 12 Mar 2014 — Following progressive medial knee pain, stiffness and recurrent effusions from post-traumatic medial compartment osteoarthritis, with bone-on-bone narrowing on standing X-ray, the orthopaedic surgeon performed a right medial unicompartmental knee replacement. He was re-mustered from infantry to supply operator. Mild osteoarthritis of the patellofemoral and lateral compartments was noted at surgery. "R medial unicompartmental knee replacement"
• 06 Jun 2016 — Annual orthopaedic review of the knee replacement. The veteran reported anterior and lateral knee aching with heavy lifting at work. There was no effusion and no swelling or fullness in the popliteal fossa. X-rays showed a well-fixed prosthesis and progression of patellofemoral and lateral compartment osteoarthritis. "no popliteal swelling, PFJ OA"
• 18 Aug 2016 — Presentation to the garrison medical officer with two weeks of tightness and a lump behind the right knee, worse after standing and lifting at work, and a recurrent knee effusion. There was a 5 cm soft, fluctuant swelling in the medial popliteal fossa that was firmer in extension. Ultrasound the same day showed a popliteal cyst arising from the gastrocnemius-semimembranosus bursa, with a joint effusion and synovial thickening. Aspiration of the knee yielded non-inflammatory fluid consistent with osteoarthritic synovitis. "popliteal cyst, effusion, synovitis"
• 02 Jun 2018 — During warlike service in Iraq the veteran twisted his right knee while turning with a box in a stores container. He developed lateral knee pain, catching and a moderate effusion. The role 2 medical officer recorded lateral joint line tenderness and a positive McMurray test, suspected an acute lateral meniscal tear and prescribed analgesia. No MRI or orthopaedic review was available, and he continued his duties. "R knee twist, lateral meniscal tear"
• 14 Jun 2018 — While unloading boxes of 15 to 25 kg from a truck by hand for about three hours in 42 degree heat, the veteran felt sudden pain behind the right knee that spread into the calf, followed by calf swelling. At the role 3 facility a deep vein thrombosis was excluded on ultrasound, which showed a ruptured popliteal cyst with fluid dissecting into the medial gastrocnemius. He was rested for five days and returned to duties. "ruptured popliteal cyst, DVT excluded"
• 11 Sep 2018 — After return to Australia MRI confirmed a complex lateral meniscal tear with synovitis and a recurrent, enlarged popliteal cyst measuring 7 cm, with residual fluid in the calf. The Oxford Knee Score had fallen from 34 in 2016 to 19. The orthopaedic surgeon recommended revision to total knee replacement. "lateral meniscal tear, cyst 7 cm"

Symptoms

At onset the veteran had a soft swelling and tightness behind the right knee, aching in the back of the knee after standing and lifting, stiffness on bending and a recurrent knee effusion. Symptoms worsened through each working day and settled partially overnight.

After the 2018 worsening he had a sudden onset of pain behind the knee spreading into the calf with calf swelling, followed by a larger, more painful cyst, catching and locking from the lateral meniscal tear and a limp. He now cannot kneel or squat, has posterior knee pain after walking more than 20 minutes and needs a stick on uneven ground.

Imaging

• 14 Dec 2006 — X-ray right knee: "Large joint effusion. No fracture. Joint spaces preserved."
• 18 Aug 2016 — Ultrasound right popliteal fossa: "Fluid-filled cyst 48 x 22 x 20 mm arising between the medial head of gastrocnemius and the semimembranosus tendon, communicating with the knee joint. Moderate joint effusion with synovial thickening."
• 14 Jun 2018 — Ultrasound right calf and popliteal fossa: "No deep vein thrombosis. Collapsed popliteal cyst with irregular margins and a fluid collection tracking into the medial gastrocnemius, consistent with cyst rupture."
• 11 Sep 2018 — MRI right knee: "Medial unicompartmental knee replacement in place. Complex tear of the posterior horn of the lateral meniscus. Moderate effusion with diffuse synovitis. Recurrent popliteal cyst 70 x 30 x 28 mm with debris and residual fluid in the medial gastrocnemius. Patellofemoral and lateral compartment osteoarthritis."

Onset Date

The most likely date of onset of this condition is 05 Aug 2016.

At that date the veteran was serving full time in Australia as a supply operator at a logistics unit, lifting and carrying stores and loading trucks daily. He had a right medial unicompartmental knee replacement, performed on 12 March 2014, and progressive patellofemoral and lateral compartment osteoarthritis following the meniscal tear he sustained in Afghanistan in 2006. On 05 August 2016 he noticed tightness and a swelling behind the right knee.

This date is appropriate because the orthopaedic review of 06 June 2016 found no effusion and no swelling or fullness in the popliteal fossa, and he first presented with the cyst on 18 August 2016, two weeks after he noticed it, when ultrasound confirmed it. It falls within uninterrupted full-time service.

For the synovitis factor, the Statement of Principles requires the injury or disease causing synovitis to be present at the time of onset; osteoarthritis of the right knee was established by 06 Jun 2016 and the synovitis it caused was shown by effusion, synovial thickening on ultrasound and joint aspiration on 18 Aug 2016. For the knee replacement factor, the replacement must be before onset; the medial unicompartmental knee replacement was performed on 12 Mar 2014, 29 months before 05 Aug 2016.

For the worsening factors, the cyst was established and documented from August 2016. The clinical worsening, with rupture of the cyst, occurred on 14 Jun 2018 in Iraq. The synovitis factor at worsening is met by the lateral meniscal tear of 02 Jun 2018 and the osteoarthritis, both causing an effusion and synovitis on 14 Jun 2018. The knee replacement of 12 Mar 2014 was in place before the worsening. The rupture occurred while he was unloading boxes by hand at an intensity of about 6 METs, at the time of the worsening. From 02 Jun 2018 to his return on 25 Jul 2018 he could not obtain appropriate clinical management in Iraq.

1. What is the formal diagnosis of the condition claimed above?

The formal diagnosis is Right Knee - Popliteal Cyst (Baker's cyst) (ICD-10-AM M71.2), complicated by rupture, under the Statements of Principles concerning popliteal cyst, Balance of Probabilities No. 32 of 2018 and Reasonable Hypothesis No. 31 of 2018.

A popliteal cyst is a swelling in the popliteal fossa behind the knee due to enlargement of the gastrocnemius-semimembranosus bursa, which communicates with the knee joint. In adults it almost always follows a disorder inside the knee that causes synovitis and an effusion, such as a meniscal tear, osteoarthritis or inflammatory arthritis. Joint fluid is forced into the bursa during knee movement and a one-way valve effect traps it there. Popliteal cysts cause posterior knee swelling, tightness, pain and stiffness, and they can enlarge, dissect into the calf or rupture, producing sudden calf pain and swelling that mimics a deep vein thrombosis.

In this veteran the cyst began on 05 August 2016 following post-traumatic osteoarthritis and a unicompartmental knee replacement, and it worsened and ruptured on 14 June 2018 during warlike service in Iraq.

2. For each diagnosis identified, please also provide the following dates:

When did the veteran first experience symptoms attributable to this condition?

05 August 2016.

When did the veteran first present to a health / medical provider for this condition?

18 August 2016.

When was the condition confirmed / formally diagnosed?

18 August 2016.

When did the veteran first present to you (or your practice) for this condition?

15 October 2025.

3. How was this diagnosis confirmed? i.e. what were the key symptoms and signs, investigation results, specialist opinions?

The diagnosis was made on 18 August 2016 on a palpable, fluctuant swelling in the medial popliteal fossa with posterior knee tightness and a recurrent effusion, confirmed the same day on ultrasound as a fluid-filled cyst arising between the medial head of gastrocnemius and the semimembranosus tendon and communicating with the knee joint. This meets the Statement of Principles definition of popliteal cyst: a swelling in the popliteal fossa due to enlargement of the gastrocnemius-semimembranosus bursa associated with clinical manifestations.

The rupture on 14 June 2018 was confirmed on ultrasound, which excluded a deep vein thrombosis and showed a collapsed cyst with fluid dissecting into the medial gastrocnemius. MRI on 11 September 2018 confirmed a recurrent, enlarged cyst with synovitis and a lateral meniscal tear. Other popliteal masses, including a popliteal artery aneurysm, a ganglion and a soft tissue tumour, were excluded on imaging.

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 05 August 2016, 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, including the supply duties and the knee replacement in Australia. The Reasonable Hypothesis instrument applies to the veteran's warlike service in Afghanistan in 2006, where the meniscal tear that led to the osteoarthritis and knee replacement occurred, and in Iraq in 2018, where the cyst worsened and ruptured.

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 Popliteal Cyst, No. 32 of 2018

Causative factors

Factor 8(1): having an injury or disease which causes synovitis of the affected knee joint at the time of the clinical onset of popliteal cyst; — MET

- At the onset on 05 August 2016 the veteran had osteoarthritis of the patellofemoral and lateral compartments of the right knee, shown on X-ray on 06 June 2016, causing synovitis with a recurrent effusion and synovial thickening on ultrasound on 18 August 2016, and non-inflammatory osteoarthritic fluid on aspiration. Osteoarthritis is listed in the Statement of Principles as an example of a disease causing synovitis. The osteoarthritis followed the service meniscal injury and meniscectomy and progressed with the heavy lifting, squatting and kneeling of his infantry and supply duties.

Factor 8(2): having a partial or total knee replacement before the clinical onset of popliteal cyst; — MET

- The veteran had a right medial unicompartmental knee replacement, a partial knee replacement, on 12 March 2014, 29 months before the onset on 05 August 2016. It was performed and funded by Defence while he was serving, for post-traumatic osteoarthritis that followed his service meniscal tear.

Worsening factors

Factor 8(3): having an injury or disease which causes synovitis of the affected knee joint at the time of the clinical worsening of popliteal cyst; — MET

- On 02 June 2018 the veteran sustained an acute lateral meniscal tear of the right knee while turning with a box in a stores container, with a moderate effusion recorded by the medical officer and a complex lateral meniscal tear and diffuse synovitis confirmed on MRI on 11 September 2018. Together with the established osteoarthritis, this caused synovitis at the time of the worsening and rupture on 14 June 2018. An acute meniscal tear is listed as an example in the Statement of Principles. The injury occurred in the course of his duties.

Factor 8(4): having a partial or total knee replacement before the clinical worsening of popliteal cyst; — MET

- The medial unicompartmental knee replacement of 12 March 2014 was in place before the worsening of the cyst on 14 June 2018, as confirmed on MRI on 11 September 2018.

Factor 8(5): for clinical worsening of a popliteal cyst manifesting as rupture of a popliteal cyst only, undertaking physical activity at a minimum intensity of five METS at the time of the clinical worsening of popliteal cyst; — MET

- The worsening on 14 June 2018 manifested as rupture of the cyst, confirmed on ultrasound the same day. At the time of the rupture the veteran had been unloading boxes of 15 to 25 kg from a truck by hand for about three hours, repeatedly squatting, lifting and carrying, an activity of about 6 METs. This was part of his supply duties.

Factor 8(6): inability to obtain appropriate clinical management for popliteal cyst. — MET

- After the lateral meniscal tear on 02 June 2018 and the rupture of the cyst on 14 June 2018 there was no orthopaedic surgeon, MRI or arthroscopy available, and the knee effusion was not aspirated. He was rested for five days and returned to lifting duties until 25 July 2018. Definitive imaging was not obtained until 11 September 2018, by which time the cyst had recurred and enlarged to 7 cm. Under Brew v Repatriation Commission (1999) this is an inability to obtain appropriate clinical management.

Reasonable Hypothesis — Statement of Principles concerning Popliteal Cyst, No. 31 of 2018

Causative factors

Factor 8(1): having an injury or disease which causes synovitis of the affected knee joint at the time of the clinical onset of popliteal cyst; — MET

- The osteoarthritis causing synovitis of the right knee at onset on 05 August 2016 was post-traumatic. It followed the acute bucket-handle tear of the medial meniscus sustained on warlike service in Afghanistan on 14 December 2006 and the partial meniscectomy that treated it on 10 May 2007.

Factor 8(2): having a partial or total knee replacement before the clinical onset of popliteal cyst; — MET

- The medial unicompartmental knee replacement of 12 March 2014, before the onset on 05 August 2016, was required for post-traumatic osteoarthritis resulting from the meniscal tear sustained on warlike service in Afghanistan in December 2006.

Worsening factors

Factor 8(3): having an injury or disease which causes synovitis of the affected knee joint at the time of the clinical worsening of popliteal cyst; — MET

- The acute lateral meniscal tear of 02 June 2018 was sustained during warlike service in Iraq and caused an effusion and synovitis at the time of the worsening and rupture on 14 June 2018, on a background of post-traumatic osteoarthritis from the 2006 Afghanistan injury.

Factor 8(4): having a partial or total knee replacement before the clinical worsening of popliteal cyst; — MET

- The partial knee replacement of 12 March 2014, required because of the 2006 meniscal tear on warlike service in Afghanistan, was in place before the worsening on 14 June 2018 during warlike service in Iraq.

Factor 8(5): for clinical worsening of a popliteal cyst manifesting as rupture of a popliteal cyst only, undertaking physical activity at a minimum intensity of five METS at the time of the clinical worsening of popliteal cyst; — MET

- The cyst ruptured on 14 June 2018, during warlike service in Iraq, while the veteran was unloading 15 to 25 kg boxes from a truck by hand for three hours in 42 degree heat, an activity of about 6 METs.

Factor 8(6): inability to obtain appropriate clinical management for popliteal cyst. — MET

- During warlike service in Iraq from 02 June to 25 July 2018 there was no orthopaedic care, MRI, arthroscopy or joint aspiration, and the veteran continued heavy lifting duties after the meniscal tear and the cyst rupture, before the cyst recurred and enlarged.

The % contribution of the causes is 100% and significant.

Sequelae

The ruptured and recurrent popliteal cyst caused calf swelling and pain, a limp and loss of knee flexion, and it contributed to the recommendation for revision to a total knee replacement. The altered gait has caused left knee and lower back pain. These are sequelae of the accepted condition and should be considered in any related claim.

Unintended Consequence

Met. The medial unicompartmental knee replacement of 12 March 2014, performed and paid for by Defence while the veteran was serving, is a recognised cause of popliteal cyst through polyethylene wear and altered knee mechanics, and the cyst is in part an unintended consequence of that treatment (section 6A of the DRCA and the equivalent provisions of the MRCA).

Inability to Attain Appropriate Medical Management

MET. From 02 June 2018 to his return on 25 July 2018, during warlike service in Iraq, the veteran's knee and popliteal cyst could not be appropriately managed. After an acute lateral meniscal tear and then rupture of the cyst there was no orthopaedic surgeon, MRI, arthroscopy or joint aspiration, and he returned to heavy lifting after five days. MRI in September 2018 showed the cyst had recurred and enlarged to 7 cm and his Oxford Knee Score had fallen from 34 to 19. Applying the objective and subjective tests in Brew v Repatriation Commission (Full Federal Court, 10 September 1999, Merkel J), operational constraints that prevent investigation and 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

1. 14 Dec 2006, Role 3 hospital record and X-ray right knee, Afghanistan
2. 10 May 2007, Operation report, Orthopaedic surgeon
3. 12 Mar 2014, Operation report, Orthopaedic surgeon
4. 06 Jun 2016, Orthopaedic review and X-ray right knee, Orthopaedic surgeon
5. 18 Aug 2016, Outpatient health record and ultrasound, Medical Officer, Garrison health centre
6. 02 Jun 2018, Role 2 medical facility record, Medical Officer, Iraq
7. 14 Jun 2018, Role 3 facility record and ultrasound, Iraq
8. 11 Sep 2018, MRI right knee and orthopaedic review, Orthopaedic surgeon
9. Statement of Principles concerning Popliteal Cyst (Balance of Probabilities) No. 32 of 2018, Repatriation Medical Authority
10. Statement of Principles concerning Popliteal Cyst (Reasonable Hypothesis) No. 31 of 2018, Repatriation Medical Authority