Presentation on several osteochondral and subchondral conditions in the knee joint.

1. Surgical Treatment of
Symptomatic Subchondral Activity
(or Bone Marrow Oedema or Bone Marrow Lesion)
What are we treating? Why? How?
Mr Vladimir Bobić, MD FRCS Ed, Consultant Orthopaedic Knee Surgeon
Chester Knee Clinic, Chester UK
www.kneeclinic.info office@kneeclinic.info @ChesterKnee

2. The entire presentation is available on: www.slideshare.net/vbobic
ICRS Approved Knee & Ankle Course
Wrocław, Poznań, Poland, 8th & 9th October 2020

3. MARIARC MRI, UK (1997)
The orange pixels correspond to normal T2 values for bone. The blue and
purple pixels are anomalous: the T2 relaxation times are elevated because the
tissue is "wetter" than normal (the fluid interface between recipient and
donor bone).
OAT MRI analysis
MR Imaging Protocol 1997: Dr David Ritchie, Consultant Musculoskeletal Radiologist, Liverpool (now Glasgow), UK

4. Osteochondral Functional Unit
Source: Dr Carl Winalski, Boston, USA, 2003
CKC UK

5. The Structure of Subchondral Bone
Redrawn from: Imhof H, Breitenseher M, Kainberger F, Rand T, Trattnig S. (1999): Importance of subchondral bone to
articular cartilage in health and disease. Top Magn Reson Imaging 10:180–192
A surprisingly high number of arterial and venous vessels, as well
as nerves, can be seen in the subchondral region sending tiny
branches into the calcified cartilage …

6. The Terminology is a Bit Confusing …
• We have a problem at the outset: what are we actually talking
about? How do we treat a wide range of osteochondral problems which
are still poorly defined and understood?
• Bone Bruise (BB): a transient traumatic event = a series of trabecular
microfractures. No surgical treatment required.
• Bone Marrow Oedema (BME): MRI evidence of increased subchondral
metabolic activity. Remodelling or reparative process, or a failure of
subchondral remodelling or repair = a degenerative process? Initially a
reparative process, but if persistent it is probably a degenerative process
(often associated with initial formation of subchondral cysts, which are a
consequence of failed local repair). No surgical treatment required, but …
• Transient Osteoporosis (TOP): no history of trauma, the knee pain is
spontaneous and disabling, exacerbated on weight-bearing. Usually gets
better over many months, back to normal MRI and clinically. When
multiple joints are involved (in approx. 40% of patients) the condition is
referred to as Transient Regional Migratory Osteoporosis (TRMO).
No surgical treatment required.
CKC UK

7. The BME is not necessarily a problem!
CKC UK

8. No Edema in Bone Marrow Edema!
• The correlation of bone marrow lesions with pain in knee OA has been
convincingly established. Here, another compelling association is established
between bone marrow (edema) lesions and risk for progression of knee OA.
What remains to be established is the cause-and-effect relationship between
the various variables.
• It is interesting that, histologically, the lesions that appear as bone
marrow edema on MRI contain very little edema at all. Rather, they
demonstrate fibrosis, osteonecrosis, and extensive bony REMODELLING
and are likely the result of contusions and focal microfractures.
• Also, it is not clear, whether an initial injury to articular cartilage
leads to mechanical malalignment and subsequent subchondral bone
destruction or rather subchondral bone damage leads to mechanical
malalignment and subsequent articular cartilage destruction.
Does bone marrow edema predict progression of knee arthritis?
A summary of Felson’s 2001 and 2003 AIM articles written by Jon Gilles, M.D., The John Hopkins Arthritis Center, 2003.
http://www.hopkins-arthritis.org/arthritis-news/2003/bone_edema_oa.html

9. Conclusion:
A majority of acutely
ACL injured knees
(92%) had a cortical
depression fracture,
which was associated
with larger BME
volumes.
This indicates strong
compressive forces
to the articular
cartilage at the time
of injury, which may
constitute an additional
risk factor for later
knee OA development.
CKC UK

10. ACL injury + extensive BB
CKC MRI 110206
Gone after 7 months
Traumatic bone bruise = many local microtrabecular fractures
CKC UK

11. MFC ACI, 6/12: “In the medial
compartment, the ACI graft has
been placed over the central
weight-bearing portion of the
medial femoral condyle. Small
cartilage flap at the interface
peripherally in keeping with
minor delamination but
otherwise the graft appears good
with no cartilage overgrowth or
major defects. The
inhomogeneity of the implant
cartilage and mild marrow
oedema-like signal beneath
the graft are expected normal
findings 6 months after the
procedure.”
Unedited MRI report Dr
David Ritchie, Glasgow, UK
CKC MRI 260906
“Normal” Bone Marrow Oedema 6/12 after MFC ACI

12. CKC UK
BME After ACI: Quite Common After 3 Years

13. Long term ACI FU & MRI and BME
CKC UK
VB: I know, but for how long?

14. CKC UK
Spontaneous BME + Insufficiency Fracture

15. Transient Osteoporosis – Extreme Bone Remodeling?
CKC UK
• The aetiology of TO and TRMO remains unclear:
• One of the likely explanations for the pathogenesis of TO is perhaps
that proposed by Frost and others.
• He stated that under noxious tissue stimuli, the ordinary biological
processes, including blood flow, cell metabolism and turnover
and also tissue modelling and remodelling, might be greatly
accelerated, called the Regional Acceleratory Phenomenon
(RAP). In his opinion a prolonged or exaggerated RAP in which a
large number of bone turnover foci are activated, is the cause of
TO.
• It has been hypothesized that symptoms may be related to bone
marrow edema demonstrated at MRI and to a transitory regional
arterial hyperflow observed at the early scintigraphic analysis.
Bone tissue micro damage is the most frequent noxious
stimulus that provokes RAP and bone tissue micro fracture
is the main consequence.
• Several elements support this hypothesis. The repeatedly observed
histological findings in patients with TO showing mild inflammatory
changes and osteoporosis, associated with an elevated bone
turnover with increased bone resorption and reactive bone
formation are a good description of ongoing TRMO.

16. Transient Regional Migratory Osteoporosis:
MRI report: “The diffuse bone marrow oedema pattern with development of subchondral linear fractures
would therefore suggest regional migratory osteoporosis rather than typical SONK lesions.”

17. Shifting Bone Marrow Oedema = Remodelling Overdrive?
Shifting Bone Marrow Oedema is a self-contained disorder involving both femoral
condyles. On MRI it exhibits vast marrow oedema and is most likely an event on the SONK
timeline. Gets better (asymptomatic), eventually!
CKC UK

18. The Terminology is Even More Confusing …
• Spontaneous Osteonecrosis (SONK): is the term used to describe a
subchondral insufficiency fracture that causes osteonecrosis. MRI
appearance: a thin linear hypointense subchondral focus on T1W and T2W
that blends in with overlying cortex and is typically surrounded by
diffuse BME. With or without subchondral fractures/deformity.
• Avascular Necrosis (AVN): an osteonecrotic lesion, low signal rim on
T1W and double line sign on T2W, with or without BME. The necrotic focus
often extends some distance away from the articular margin and may
contain fat, blood, fluid, fibrous tissue. With or without subchondral
fractures/deformity.
• Osteochondritis Dissecans (OCD): semidetached osteochondral
fragment (essentially a non-union) with fluid layer at osseous interface and
seemingly intact articulating surface. A traumatic or metabolic event, or
both?
• Secondary Osteoarthrosis (not –itis): if localized, this is perhaps the
end result of more extensive progressive failure of subchondral
remodelling. Increased but unsuccessful subchondral activity (progressive
BME + multiple cysts?) seems to be a primary event, with secondary loss
of articulating surface, which fails gradually as it is not supported by
normal elastic trabecular bone. May go as far back as injury-induced BB,
with or without visible initial chondral damage.
CKC UK

19. BME and Insufficiency Fracture
Recent localised incomplete subarticular fracture of the outer aspect of the MFC (15 x 5 x 3
mm) with slight depression of the overlying articular cortex and prominent surrounding
marrow and soft tissue oedema but no obvious disruption of the overlying articular
cartilage or unstable osteochondral fragment.
CKC UK

20. Insufficiency Fracture and BME
CKC UK

21. SONK (Spontaneous Osteonecrosis)
CKC UK

22. Post-arthroscopy Spontaneous Osteonecrosis (SONK)
• Ahlback et al first described
spontaneous osteonecrosis of the
knee as a distinct clinical entity in
1968.
• Osteonecrosis of the knee has also
been described as a postsurgical
complication following
arthroscopic meniscectomy
(Muscolo et al., Prues-Latour et al.)
and following radiofrequency-
assisted arthroscopic treatments,
mainly in 50+ age groups.
• The pathophysiology of osteonecrosis
following these arthroscopic
procedures is not fully understood
(vascular isufficiency, trabecular
microfractures?), or, more likely, a
consequence of pre-arthrosopy
osteopoenia and altered focal
biomechanics (bone density
should be looked into).
CKC UK

23. Post-arthroscopy BME (SONK?)
CKC UK 2018

24. SONK Before and After Subchondral Decompression
• 15/12/08: subarticular
insufficiency fracture and slight
flattening of the MFC and prominent
subarticular marrow oedema more
marked on the femoral side. Since
04/04/08, significant deterioration
in the medial compartment with
SONK-like process, progressive
degenerative changes …
• 11/09/09: Comparison is made with
the previous scan 15/12/2008. In
the medial compartment, following
the subchondral decompression,
there is now evidence of
articular irregularity, deficiency
and thinning of articular
cartilage, slight increase in the
subarticular marrow oedema
and early subarticular cyst
formation in the outer aspect of
the MFC …
CKC UK

25. Insufficiency Fracture and BME - Things get better, given time!
CKC UK

26. CKC UK
Spontaneous SONK + Insufficiency Fracture:
relatively asymptomatic, getting better slowly …

27. SONK (Spontaneous Osteonecrosis)
with Residual Insufficiency Fracture
CKC UK

28. Symptomatic Treatable Subchondral Cyst (with CP and BMC)
CKC UK

29. CKC UK
Subchondral Cysts Are Not Good But Do not Need Treatment

30. CKC UK
Symptomatic Treatable MTC BME (with intraosseous BMA)

31. Subchondroplasty
Procedure with CP

32. Subchondroplasty: 1st Take Home Message:
CKC UK

33. CKC UK

34. The 1st report on complications after
a calcium phosphate subchondroplasty
CKC UK

35. CKC UK

36. The CP Subchondroplasty Procedure:
Arguably, subchondroplasty with bone substitute is indicated mainly for the
treatment of subchondral cysts and cavities, rather than various bone marrow
oedema conditions.
Bone marrow oedema, as metabolic (vascular) “event” does not lack bone
(therefore injecting bone substitute is not the right ingredient). To the contrary,
injecting bone paste will clog many interconnected cellular spaces and will slow
down or prevent subchondral repair and remodelling.
Injected and cured bone paste will increase intra-osseous pressure (which is
already higher than normal and which is why SONK-like conditions are very painful
to start with) and block metabolic (vascular) pathways!
However, the real (biologically) desirable ingredient is autologous bone marrow
aspirate (or autologous stem cells or even PRP), delivered to the area affected
with bone marrow oedema.
Vladimir Bobic CKC: Articular Cartilage, Subchondral Bone and Osteochondral Unit. 4th BKS Meeting, Cardiff, UK 1-2 February 2018.

37. The Importance of Autologous Bone Marrow
CKC UK
Dr Philippe Hernigou, Paris

38. James Cook, UMSM “Pre-TKR” option: OATS combined with ABMC

40. Targeted Intraosseous Delivery of Autologous Bone Marrow
CKC UK

41. Symptomatic Medial OA + BME: PT Declined UKR or HTO
CKC UK

42. Asymptomatic Medial OA + BME 1 Year After OATS + SCD + ABMI
CKC UK

43. Other Take Home Messages …
Do you really have to treat painful bone marrow
oedema? Think twice!
Do not treat MR images - treat the patient, holistically!
Take time: wait, review, repeat the scan …
If you decide to treat “symptomatic bone marrow
oedema”, discuss everything with the patient and
document everything.
Do not use bone substitutes, use autologous bone
marrow.
Do not restrict WB and ROM!
And finally, remember:
CKC UK

44. … and the Last Take Home Message:

45. Thank You for Your Attention
Everything We Know About
Articular Cartilage
A Lot More We do Not Know About
Subchondral Bone and
Osteochondral Unit
(Known and Unknown Unknowns)
www.slideshare.net/vbobic
CKC UK