Cartilage Defects

Chondral Defect Medial Femoral CondyleKnee OCD Arthroscopy Type 4




Anatomy / Biochemistry


Constituents of cartilage


1. Type II collagen

- triple helix

- provides tensile strength and mechanical integrity

- 50% of dry weight


2. Proteoglycans

- 10%

- glycosaminoglycans with keratan sulphate and chondroitin sulphate

- negative charge has high affinity for water


3.  Water

- 65-85% of weight

- highly attracted to GAG

- resistant to compressive loads


4.  Chondrocytes

- 2% weight

- low oxygen, avascular environment

- anaerobic metabolism

- make collagen and GAG


Structure of cartilage


Superficial zone

- 10-20%

- arranged parallel to surface


Intermediate zone

- more haphazard


Deep zone

- chondrocytes in columns

- perpendicular


Calcified Zone / tidemark

- above subchondral bone

- any mitotic ability of chondrocytes ceases when this develops




Inability to heal

- avascular

- nil pluripotent cells in maturity

- nil mitotic ability

- limited synthetic ability in adult


Some ingrowth from sides can occur

- healing size dependant

- 3 mm lesion will heal

- 9 mm will not



- loss of cartilage results in loss of water and increased stiffness in remainder

- vicious cycle of continued damage

- nil ability to heal unless penetrates thick subchondral bone

- allows bleeding and primitive mesenchymal cells

- typically produce fibrocartilage




Chondral Defect Full Thickness






Grade 1: Softening and swelling of the cartilage

Grade 2: Fragmentation and fissuring in an area half an inch or less in diameter

Grade 3: Same as grade 2 but an area more than half an inch in diameter is involved

Grade 4: Erosion of cartilage done to bone



- difference between grade 2 and 3 is size

- depth is probably more of an issue


ICRS / International Cartilage Research Society


Grade 0: Normal


Normal Hyaline Cartilage


Grade 1: Nearly normal / soft indentation and/or superficial fissures and cracks


Grade 1 Cartilage LesionGrade 1 Chondral Lesion Femur


Grade 2: Abnormal (lesions extending down to < 50% of cartilage depth)


Grade 2 Chondral Lesion


Grade 3:  Severely abnormal (cartilage defects > 50% of cartilage depth)


MFC Grade 4 LesionICRS Grade 3 Chondral Lesion


Grade 4: Severely abnormal (through to the subchondral bone)


Grade 3 Chondral InjuryICRS Grade 4 Chondral Lesion




5mm graduated probe

- tend to overestimate size arthroscopically


Measure in 2 dimensions

- give a size in cm2

- assumes that lesions are basically rectangular


Chondral Lesion 5 mmChondral Width Measurement


Treatment Algorithms



- grade 3 or 4 ICRS lesions


Niemeyer et al Arthroscopy 2011

- lesions < 4cm2 microfracture

- lesions > 4cm2 or failed microfracture ACI


Cole et al JBJS 2009

- < 2 - 3 cm2 with microfracture or OATS (osteochondral allograft transplantation)

- > 2 - 3 cm2 with osteochondral allograft (OCA) or autologous chondrocyte implantation (ACI)

- trochlea - microfracture or ACI + anteromedialization of the trochlea


Brittberg 2003

- osteochondral lesions < 8mm deep can be managed with ACI

- osteochondral lesions > 8mm deep require bone graft / ACI or OATS


1.  Microfracture / drilling


Microfracture Chondral Defect InitiallyMicrofracture Post PreparationMicrofracture Awl Holes



- pluripotent marrow cells

- produce fibrocartilage to varying degree

- principally type 1 cartilage

- low stiffness and poor wear characteristics over time

- may be more beneficial to combine with realignment procedure



- young patient

- contained defect

- best results < 2 cm2

- BMI < 30

- age < 40

- need cartilage on each side to contain clot



- axial malalignment

- uncontained lesion (edge of condyles / intercondylar notch


Chondral Defet Uncontained


Technique (Steadman J Knee Surg 2002)


1.  Debride all unstable cartilage to stable edge

- removed calcified cartilage layer with curette, protect subchondral bone

- create a perpendicular edge which helps to hold the superclot

- if there is a great deal of subchondral sclerosis may remove with arthroscopic burr

- until reveal punctate bleeding


Microfracture Currette BaseMicrofracture Arthroscopic Awl


2.  Arthroscopic awl

- usually have bend of 30o (Steadman Pick)

- typically 3-4 mm apart

- depth until see fat globules (2-3 mm)

- start at periphery and finish at centre

- will see blood oozing if drop pump pressure / turn off tourniquet / apply suction


Microfracture Awl Holes Pre SuctionMicrofracture Awl Holes Bleeding


Post op


NWB 8/52

Full passive ROM

Brace locked 0 - 20o for PFJ

ROM brace to prevent varus / valgus

No running for 3/12

No sports for 6/12




Patients may feel catching of perpendicular edge

- will resolve over time


Swelling common for 6-8 weeks




Knutsen et al JBJS Am 2007

- prospective RCT ACI v microfracture

- 77% good results in both groups at 5 years


Steadman et al Am J Sports Med 2004

- combined microfracture and HTO in patients with varus > 5o

- effective at reducing pain and improving function


2.  Membranous Autologous Cartilage Implantation






Transplant living viable cells

- capable of synthesising and maintaining a cartilaginous matrix

- makes a substance physically and histologically similar to hyaline cartilage



- cells presented on a membrane for implant

- ACI have to harvest periosteum to secure cells in place




Nil instability

Nil malalignment




Doesn't deal with bony defect

- only cartilage defect


Technique Harvest


Harvest mature chondrocytes


Biopsy taken from NWB area

- in notch or lateral edge of femoral cartilage

- use small punch, take 5 - 6 very small bites


Placed in tubes of saline for transport

- provided by company

- blood taken to isolate serum

- cells isolated and washed

- expanded in cell culture

- attached to membrane

- process takes about six weeks


Technique Implantation



- medial or lateral parapatellar

- if lateral lesion very large, may need medial parapatellar approach to evert patella

- cut through retinaculum in extension so can pull up tissue towards knife and avoid cutting femoral condyle

- distally often have to make small radial incision in meniscus which can be repaired afterwards

- again, take care to protect the tibial plateau cartilage



- use knife to cut cartilage edge to sharp stable margin

- use curette at base, but must keep subchondral plate intact to prevent bleeding

- excess bleeding will wash away graft

- options to control bleeding involve the use of adrenalin soaked gauze or fibrin glue



- use foil from suture pack and cut to size

- want graft to be undersized rather than oversized

- needs to fit into defect and not overlap edges

- in this way it will be stable and not be torn away with ROM

- place onto membrane

- must ensure that the cartilage cell side (which look rough) will be placed down



- run fibrin glue from above down

- will set quickly

- take graft off paper and insert

- finger digital pressure whilst glue sets

- reassess MACI and check edges are not overhanging

- trim with scissors if needed

- ensure is stuck down (can reapply glue and re-pressurise)



- do a rough aggressive ROM to ensure is graft stable 


Post op


NWB 8/52

- limit ROM to 90o for 6 weeks

- no sports minimum 6 months




Ebert et al Am J Sports Med 2011

- 5 year clinical and MRI follow up of 41 patients

- 90% good or excellent filling of chondral defect on MRI

- 86% able to do ADL's

- 76% able to return to sport


3.  Autologous Chondrocyte Implantation






1.  Harvest a periosteal graft form proximal medial tibia

- medial or lateral parapatellar approach

- nothing done to subchondral plate to prevent any bleeding

- place periosteum cambium layer down

- suture in place with 6.0 Dexon / Vicryl

- seal edges with fibrin glue except with one corner

- inject cells, seal edge with fibrin glue


2.  Porcine collagen ACI-C




Bartlett et al JBJS Br 2005


- arthroscopic review at one year

- 80% good cartilage in ACI v 66% in MACI

- similar clinical outcomes in each


4.  Mosaicplasty / Osteochondral Autograft Transplant / Osteochondral Allograft Transplantation (OATS)


Pre MosaicplastyChondral Defect Post MosaicplastyOsteochondral Allograft


Chondral DefectDefect debridedHarvestMosaicplasty




Take bone plugs on bone and cartilage

- implant in defect

- get coverage with normal hyline cartilage

- also deals with bone defect




Prepare Defect

- debride all tissue from defect

- create cylindrical holes with drill


Donor sites

- periphery of femoral trochlea

- trochlea notch

- plug size 4.5 mm usually



- fill with plugs of bone and cartilage in mosaic fashion

- fill 60 - 80%

- slightly recess cartilage on plugs

- attempt to match radius of curvature


Post op


MRI at six months

- assess cartilage regrowth


Mosaicplasty MRI Post Implantation Good Cartilage CoverMosaicplasty MRI Post Implantation Sagittal Good Cartilage Cover




Hangody et al Am J Sports Med 2010

- 354 patients followed up for average 9 years

- 91% good results in femur

- 86% good results in tibia

- 74% good results in PFJ

- 92& good results in talus


Gudas et al Arthroscopy 2005

- RCT of OATS v microfracture of 60 young adults

- all with chondral defects, followed up for 3 years

- 93% OATS and 50% microfracture returned to sport


5.  Osteochondral allografts


Osteochondral Allograft PreOsteochondral Allograft PostOsteochondral Allograft




Very large, non contained defects

Restore anatomic contour

Nil donor site morbidity


Viable chondrocytes


Fresh grafts

- 70% viable

- None on frozen, irradiated grafts





- match curvature of radius of donor


Combine with HTO if any malalignment

- usually HTO for medial femoral condyle defects / in varus

- usually distal femoral osteotomy for valgus deformity


Press fit

- if surrounding by good bone




Case 1 


Osteochondral Allograft PrePost Osteochondral Allograft


Case 2


Failed OCD APOCD Failed Fixation Lateral


Osteochondral Allograft and HTO APOsteochondral Allograft HTO Lateral


Case 3


Tibial Plateau OA APTibial Plateau OA Lateral


Osteochondral Allograft Tibial Plateau0001Osteochondral Allograft Tibial Plateau0001




Gross et al CORR 2001

- 75 distal femoral osteochondral allografts

- patient average age 27, average follow up 10 years

- 68% had HTO or DRVO

- 20% graft failures (3 graft removals, 9 TKR)

- of the remaining cases, 40/48 patients had good or excellent outcome


6.  Hemicap


Knee Hemicap AP Post OCDKnee Hemicap Lateral