Arthroscopy: The Journal of Arthroscopic and Related Surgery T(2):198-203
Published by Raven Press, Ltd. 0 1991Arthroscopy Association of North America
Cartilage Lesions in the Knee of Adolescents and Young Adults: Arthroscopic Analysis Nozomu Imai, M.D. and Taisuke Tomatsu, M.D.
Summary: In this article, the mechanism of occurence and development of cartilage lesions as well as the relationship between pain and conditions of cartilage lesions will be discussed. The study was based on the findings from arthroscopic analyses, plain radiographs, and arthrograms. Sixty-five joints of 63 patients with cartilage lesions were examined. We have made the following conclusions. Cartilage lesions do not start necessarily from the surface layers of the cartilage. Lesions may originate in the subchondral bone and develop toward the surface, causing severe pain. Cartilage lesions, resulting in little pain, are related closely to joint instability, indicating that the lesion occurrence is affected by unnatural shearing stress rather than by direct force applied to the joint surface. Thus, prevention and treatment should focus on removing the shearing stress. The purpose of this article is to examine how cartilage lesions relate to patient symptoms. Additionally, untreated lesions possibly could develop into the early stage of osteoarthrosis of the knee, causing exposure of the subchondral bone and thus continuous pain. Key Words: Cartilage lesions-Surgery-Knee pain- Subchondral lesions-Shearing force.
MATERIALS
grams, and plain radiographs of each case to determine how cartilage lesions develop and how they are related to the patient’s symptoms.
AND METHODS
We studied 65 joints of 63 patients in whom cartilage changes were found during arthroscopy. Their ages ranged from 15 to 30 years. There were 22 male and 41 female patients. Forty-three knees had lesions in the patellofemoral joint; the remaining 22 knees had lesions in the tibiofemoral joint (Tables 1 and 2). We classified cartilage lesions as follows: type I: swelling with softening; type II: superficial fibrillation; type III: deep fibrillation; type IV: cartilage defect that does not go beyond the cartilage layers; and type V: cartilage defect reaching the subchondral bone (Fig. 1). Using this classification, we examined cartilage lesions by comparing arthroscopic analyses, arthro-
RESULTS
In looking at the plain radiographs, we focused on the part of the subchondral bone directly beneath the cartilage lesion. Various kinds of changes such as bone atrophy, shell-shaped separation, local bone fragmentation, and bone defect were observed. The arthrograms of the anterosposterior view in the normal cases typically showed the TABLE 1. Areas of cartilage change
Lateral femoral condyle Medial femoral condyle Patella
From the Orthopaedic Department, School of Medicine, Tokai University, Bohseidai, Isehara, Japan. Address correspondence and reprint requests to Dr. N. Imai, Orthopaedic Department, School of Medicine, Tokai University, Bohseidai, Isehara 259- 11, Japan
No.
%
17
26.2
5 43
2:;
Age range: 15-30 years; 22 male subjects (24 joints); 41 female subjects (41 joints).
198
CARTILAGE TABLE 2. Associated
LESIONS
199
lesions
Type
No. joints
Meniscal tear ACL rupture PCL rupture Collateral ligament tear No associated lesions
16 13 5 11 27
smooth surface of cartilage; the thickness of the cartilage ranged from 2.6 to 3.0 mm at the top of the convex surface of the femoral condyle (Fig. 2). In contrast, the arthrograms of the cases with lesions revealed an irregular surface, with some parts depressed or worn thin (Fig. 3). A prototypical case for each of the aforementioned five types is described below. Case 1 (type I). A 23-year-old man complained of slight pain on the inner side of the left knee. Dissection of the subchondral bone was found at the border of the medial femoral condyle on a plain radiograph and a tomogram (Fig. 4). We examined this area with arthroscopy. The surface of the car-
Type 1
Type
IN KNEE
FIG. 2. An arthrogram of normal cartilage. smooth and convex surface of the cartilage.
Arrow
shows
tilage was swollen. A soft texture was felt when pushed with a probe, but no tear was found on the cartilage. This swelling and softening of the cartilage is typical of type I (Fig. 5). Case 2 (type II). A 27-year-old female volleyball
II
FIG. 1. Classification of cartilage lesions and schematic views of each type of lesion. Type I, swelling with softening; type II, superficial fibrillation; type III, deep fibrillation; type IV, defect of the cartilage without invasion to the subchondral bone; type V, defect of the cartilage reaching the subchondral bone.
FIG. 3. An arthrogram of a cartilage lesion. Arrow points to localized depression with irregular contour on a surface of the cartilage.
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FIG. 4. A roentgenogram (tomography) of case 1. The roentgenogram shows osteochondritis dissecans in the medial femoral condyle (arrow).
player had symptoms such as “giving way” and “anterior knee pain.” She had apparent instability of the knee joint. An apprehension test of the patella was positive. A skyline view arthrography showed a bad alignment of the patellofemoral joint. The symptoms obviously were caused by malalignment of the patellofemoral joint. An arthrogram of the femoral condyle revealed wide-ranging but superficial abrasion of the cartilage (Fig. 6). An arthroscopic analysis found shallow fibrillation on the same spot (Fig. 7). Case 3 (type III). A ldyear-old girl had twisted her knee 3 weeks before coming to our clinic and had had acute pain on the rear of the patella since
then. A plain radiograph showed fragmentation of the subchondral bone in the medial facet of the patella (Fig. 8A). However, when the cartilage of the patella was observed through arthroscopy, only slight fibrillation was evident on the surface (Fig. 9A). This means the injury of the subchondral bone
FIG. 5. Arthroscopic findings of case 1. The articular cartilage of the femoral condyle seems to be normal except for slight swelling (type I lesion).
FIG. 7. Arthroscopic findings of case 2. The scopic photogram shows the type II lesion of the cartilage.
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FIG. 6. An arthrogram of case 2. Arrow indicates thin cartilage with flat surface of the medical femoral condyle.
CARTILAGE
LESIONS
IN KNEE
201
FIG. 8. A roentgenogram of case 3. A: Immediately after injury. The roentgenogram shows thin fragment of the subchondral bone (arrow) on the medial facet of the patella. B: One year after the realignment operation. Healing of fracture can be seen in the roentgenogram taken 1 year after injury. Arrow shows union of the fragment.
did not affect the cartilage. The patient underwent a realignment operation with subsequent follow-up. A radiograph showed that the fragment had reunited gradually with the bone (Fig. 8B). The pain had disappeared. However, an arthroscopic analysis performed 1 year after the injury revealed that the cartilage lesion had developed to type III (Fig. 9B). Case 4 (type IV). A 21-year old female hurdler complained of a dull pain in the right knee. An arthrogram showed an abrasion in the medial femoral condyle (Fig. IO). The arthroscopic findings (Fig. 11) showed that the cartilage lesion had not reached the subchondral bone, which makes this case prototypical for type IV. The pain disappeared spontaneously 4 weeks later. Case 5 (type V). A 31-year-old man experienced an acute pain while playing basketball. Hemarthro-
sis was recognized, but a plain radiograph did not indicate any lesion. Arthroscopy was performed, and cartilage lesions reaching the subchondral bone, known as osteochondral fractures, were observed in the posterior part of the weight-bearing area on the medial femoral condyle (Fig. 12). The number and percentage of the joints for each of the five types of cartilage lesions are as follows: type I: 4 (6.2%); type II: 26 (40%); type III: 20 (30.8%); type IV: 8 (12.3%); and type V: 7 (10.7%). DISCUSSION Because the arthroscope gives a wide-angled, detailed view of the knee joint cavity, lesions in the cartilage of young adults are more observable. However, a discussion of the development of these cartilage lesions is necessary to determine how
9A
FIG. 9. A: Arthroscopic findings of case 3. Immediately after injury. No particular lesion can be seen on the cartilage of the medial facet of the patella. B: One year after the realignment operation. Arthroscopic findings reveal type III lesion of the articular cartilage.
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FIG. 10. An arthrogram of case 4. The arthrogram shows a localized cartilage defect at the medial side of the medial femoral condyle (arrow).
these lesions progress to the later stages. Would they always proceed, or would they heal naturally? Additionally, the relationship between the symptoms and the cartilage lesion must be discussed. We have found that the arthrogram is a useful method for identifying cartilage lesions. After an arthrogram is done, arthroscopy then is performed to diagnose the lesion more specifically. Mechanism of development of cartilage lesions Most of the patients in whom we found cartilage lesions in the femoral condyle played some sort of sport placing strong forces on the knee. Twenty percent of those cases are accompanied by injuries in the meniscus. However, it should not be concluded casually that it is the direct, vertical forces that damage the cartilage. We have observed that
FIG. 12. Arthroscopic findings of case 5. Type V lesion of the cartilage can be seen on the medial femoral condyle.
the majority of the lesions started in the outside part of the femoral condyle rather than in the weightbearing part. This indicates that abduction or adduction of the knee rather than direct stress is a factor in the injury: it is a shearing stress rather than a direct force that plays a crucial role. We also found instances in which cartilage lesions developed from the deep layers of the cartilage to the surface layers rather than the more common occurrence whereby the lesion begins in the surface layers and erodes to the deeper layers. In case 1 described above, dissection of the subchondral bone in the medial femoral condyle was observed in the radiograph, but no obvious tear was found on its covering cartilage surface. However, the cartilage was soft when touched, and the case was considered to be an early stage of osteochondritis dissecans. Based on the findings above, we 13A,B
FIG. 11. Arthroscopic findings of case 4. Type IV lesion of the cartilage can be seen on the medial femoral condyle.
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FIG. 13. A: Atrophy and fragmentation of the subchondral bone of the patella, 2 weeks after dislocation of the patella (arrow). B: Hypertrophy of the subchondral bone (arrow) in the same case, 2 years after dislocation.
CARTILAGE
LESIONS
concluded that the lesion had originated in the subchondral bone and had developed gradually to the cartilage surface. Case 3 had a fracture of the subchondral bone in the medial facet caused by dislocation of the patella. The patient complained of acute pain in the corresponding area. However, arthroscopy identilied only slight flaking on the surface of the cartilage. Therefore, we concluded that the external force first damaged the subchondral bone. On follow-up, the bone fracture gradually healed after the realignment operation on the patella. As the bone fracture healed, the pain disappeared. However, on the l-year folow-up, the lesion had developed to type III. We concluded that the shearing stress that injured the subchondral bone also damaged the fibril network that lies at the bottom of the cartilage close to the bone, right beyond the tide mark. This injury to the bottom layer probably spread toward the surface layers in time. No sign of healing of the lesion, at least macroscopically, was observed. Eleven percent (live joints in the patella and two in the femoral condyle) of the knees observed in this study followed this pattern of very slight or no damage to the cartilage surface when examined using arthroscopy but obvious injuries in the subchondral bone in the radiographs. In addition, live cases were observed to have bone hypertrophy after atrophy on the subchondral bone after repeated episodes of dislocation and subluxation of the patella (Fig. 13). This also may have originated from the small injuries in the subchondral bone. We assume the reason for the injuries in the deep layers is that the shearing stress that is applied onto the surface of the cartilage is highly viscoelastic. A previous experimental study we performed obtained the results that support this assumption (1). The relationship between the pain the patient reports and cartilage lesions is difficult to evaluate objectively because there are individual differences in sensitivity to pain and other subjective factors. Furthermore, the pain could be due to the synovitis caused by cartilage lesions rather than due to the cartilage lesions themselves. However, based on our observations and findings from the cases studied, we can say that in the cases of fibrillation or defect within the cartilage layers of the femoral condyle (cases 2 and 4), the patients complained of
IN KNEE
203
little pain. In constrast, in cases 1, 3, and 5, in which the lesions penetrated the subchondral bone, the patients experienced strong pain regardless of the severity of the lesions on the cartilage surface. We assume that this indicates that the pain is related more to the lesions of the subchondral bone than to the lesions within the cartilage. As in case 3, the pain gradually decreased and eventually disappeared as the dissected bone fracture was healed, in spite of the fact that the cartilage lesions had proceeded. CONCLUSION We analyzed the nature of cartilage lesions that are found frequently in adolescent knee joints based on the findings from arthroscopy, plain radiography, and arthrograms. We suggest that unnatural shearing stresses applied to the cartilage are closely related to the occurrence and development of cartilage lesions. In fact, in many cases joint instability accompanied the cartilage lesions, whether the lesions were on the patellofemoral joint or the tibiofemoral joint. We therefore would conclude that to prevent and treat cartilage lesions, it is crucial to remove the instability in the patellofemoral and tibiofemoral joint. REFERENCES 1. Imai N, Tomatsu T, Okamoto H, Nakamura Y. Clinical and roentgenological studies on malalignment disorders of the patello-femoral joint. Part III: lesions of the patellar cartilage and subchondral bone associated with patello-femoral malalignment. J Jpn Orthop Assoc 1989;63:1-17. 2. Bauer M, Jackson RW. Chondral lesions of the femoral condyles: a system of arthroscopic classification. Arrhroscopy 1988;4:72-80. 3. Dzioba RB. The classification and treatment of acute articular cartilage lesions. Arthroscopy 1988;4:72-80. 4. Fairbank JCT. Pvnsent PB. vanpoortvliet JA. Philhus H. Mechanical factors in the incidence of knee pain in adolescents and young adults. J Bone Joint Surg [Br] 1984;66:68!593. 5. Glowacki J. Cartilage and bone repair: experimental and clinical studies. Arthroscopy 1986;2:169-73. 6. Hopkinson WJ, Mitchell WA, Curl WW. Chondral fractures of the knee. Am J Sports Med 1085;13:309-12. 7. Johnson-Nurse C, Dandy DJ. Fracture separation of articular cartilage in the adult knee. J Bone Joint Surg [Br] 1985;67:42-3. 8. Minns RJ. Cartilage ulceration and shear fatigue fracture. Lancer 1976;1:907-8. 9. Repo RU, Finlay JB. Survival of articular cartilage after controlled impact. .J Bone Joint Surg [Am] 1977;59:106&76.
Arthroscopy,
Vol. 7, No. 2, 1991
Published by Raven Press, Ltd. 0 1991Arthroscopy Association of North America
Cartilage Lesions in the Knee of Adolescents and Young Adults: Arthroscopic Analysis Nozomu Imai, M.D. and Taisuke Tomatsu, M.D.
Summary: In this article, the mechanism of occurence and development of cartilage lesions as well as the relationship between pain and conditions of cartilage lesions will be discussed. The study was based on the findings from arthroscopic analyses, plain radiographs, and arthrograms. Sixty-five joints of 63 patients with cartilage lesions were examined. We have made the following conclusions. Cartilage lesions do not start necessarily from the surface layers of the cartilage. Lesions may originate in the subchondral bone and develop toward the surface, causing severe pain. Cartilage lesions, resulting in little pain, are related closely to joint instability, indicating that the lesion occurrence is affected by unnatural shearing stress rather than by direct force applied to the joint surface. Thus, prevention and treatment should focus on removing the shearing stress. The purpose of this article is to examine how cartilage lesions relate to patient symptoms. Additionally, untreated lesions possibly could develop into the early stage of osteoarthrosis of the knee, causing exposure of the subchondral bone and thus continuous pain. Key Words: Cartilage lesions-Surgery-Knee pain- Subchondral lesions-Shearing force.
MATERIALS
grams, and plain radiographs of each case to determine how cartilage lesions develop and how they are related to the patient’s symptoms.
AND METHODS
We studied 65 joints of 63 patients in whom cartilage changes were found during arthroscopy. Their ages ranged from 15 to 30 years. There were 22 male and 41 female patients. Forty-three knees had lesions in the patellofemoral joint; the remaining 22 knees had lesions in the tibiofemoral joint (Tables 1 and 2). We classified cartilage lesions as follows: type I: swelling with softening; type II: superficial fibrillation; type III: deep fibrillation; type IV: cartilage defect that does not go beyond the cartilage layers; and type V: cartilage defect reaching the subchondral bone (Fig. 1). Using this classification, we examined cartilage lesions by comparing arthroscopic analyses, arthro-
RESULTS
In looking at the plain radiographs, we focused on the part of the subchondral bone directly beneath the cartilage lesion. Various kinds of changes such as bone atrophy, shell-shaped separation, local bone fragmentation, and bone defect were observed. The arthrograms of the anterosposterior view in the normal cases typically showed the TABLE 1. Areas of cartilage change
Lateral femoral condyle Medial femoral condyle Patella
From the Orthopaedic Department, School of Medicine, Tokai University, Bohseidai, Isehara, Japan. Address correspondence and reprint requests to Dr. N. Imai, Orthopaedic Department, School of Medicine, Tokai University, Bohseidai, Isehara 259- 11, Japan
No.
%
17
26.2
5 43
2:;
Age range: 15-30 years; 22 male subjects (24 joints); 41 female subjects (41 joints).
198
CARTILAGE TABLE 2. Associated
LESIONS
199
lesions
Type
No. joints
Meniscal tear ACL rupture PCL rupture Collateral ligament tear No associated lesions
16 13 5 11 27
smooth surface of cartilage; the thickness of the cartilage ranged from 2.6 to 3.0 mm at the top of the convex surface of the femoral condyle (Fig. 2). In contrast, the arthrograms of the cases with lesions revealed an irregular surface, with some parts depressed or worn thin (Fig. 3). A prototypical case for each of the aforementioned five types is described below. Case 1 (type I). A 23-year-old man complained of slight pain on the inner side of the left knee. Dissection of the subchondral bone was found at the border of the medial femoral condyle on a plain radiograph and a tomogram (Fig. 4). We examined this area with arthroscopy. The surface of the car-
Type 1
Type
IN KNEE
FIG. 2. An arthrogram of normal cartilage. smooth and convex surface of the cartilage.
Arrow
shows
tilage was swollen. A soft texture was felt when pushed with a probe, but no tear was found on the cartilage. This swelling and softening of the cartilage is typical of type I (Fig. 5). Case 2 (type II). A 27-year-old female volleyball
II
FIG. 1. Classification of cartilage lesions and schematic views of each type of lesion. Type I, swelling with softening; type II, superficial fibrillation; type III, deep fibrillation; type IV, defect of the cartilage without invasion to the subchondral bone; type V, defect of the cartilage reaching the subchondral bone.
FIG. 3. An arthrogram of a cartilage lesion. Arrow points to localized depression with irregular contour on a surface of the cartilage.
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N. IMAI AND T. TOMATSU
200
FIG. 4. A roentgenogram (tomography) of case 1. The roentgenogram shows osteochondritis dissecans in the medial femoral condyle (arrow).
player had symptoms such as “giving way” and “anterior knee pain.” She had apparent instability of the knee joint. An apprehension test of the patella was positive. A skyline view arthrography showed a bad alignment of the patellofemoral joint. The symptoms obviously were caused by malalignment of the patellofemoral joint. An arthrogram of the femoral condyle revealed wide-ranging but superficial abrasion of the cartilage (Fig. 6). An arthroscopic analysis found shallow fibrillation on the same spot (Fig. 7). Case 3 (type III). A ldyear-old girl had twisted her knee 3 weeks before coming to our clinic and had had acute pain on the rear of the patella since
then. A plain radiograph showed fragmentation of the subchondral bone in the medial facet of the patella (Fig. 8A). However, when the cartilage of the patella was observed through arthroscopy, only slight fibrillation was evident on the surface (Fig. 9A). This means the injury of the subchondral bone
FIG. 5. Arthroscopic findings of case 1. The articular cartilage of the femoral condyle seems to be normal except for slight swelling (type I lesion).
FIG. 7. Arthroscopic findings of case 2. The scopic photogram shows the type II lesion of the cartilage.
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FIG. 6. An arthrogram of case 2. Arrow indicates thin cartilage with flat surface of the medical femoral condyle.
CARTILAGE
LESIONS
IN KNEE
201
FIG. 8. A roentgenogram of case 3. A: Immediately after injury. The roentgenogram shows thin fragment of the subchondral bone (arrow) on the medial facet of the patella. B: One year after the realignment operation. Healing of fracture can be seen in the roentgenogram taken 1 year after injury. Arrow shows union of the fragment.
did not affect the cartilage. The patient underwent a realignment operation with subsequent follow-up. A radiograph showed that the fragment had reunited gradually with the bone (Fig. 8B). The pain had disappeared. However, an arthroscopic analysis performed 1 year after the injury revealed that the cartilage lesion had developed to type III (Fig. 9B). Case 4 (type IV). A 21-year old female hurdler complained of a dull pain in the right knee. An arthrogram showed an abrasion in the medial femoral condyle (Fig. IO). The arthroscopic findings (Fig. 11) showed that the cartilage lesion had not reached the subchondral bone, which makes this case prototypical for type IV. The pain disappeared spontaneously 4 weeks later. Case 5 (type V). A 31-year-old man experienced an acute pain while playing basketball. Hemarthro-
sis was recognized, but a plain radiograph did not indicate any lesion. Arthroscopy was performed, and cartilage lesions reaching the subchondral bone, known as osteochondral fractures, were observed in the posterior part of the weight-bearing area on the medial femoral condyle (Fig. 12). The number and percentage of the joints for each of the five types of cartilage lesions are as follows: type I: 4 (6.2%); type II: 26 (40%); type III: 20 (30.8%); type IV: 8 (12.3%); and type V: 7 (10.7%). DISCUSSION Because the arthroscope gives a wide-angled, detailed view of the knee joint cavity, lesions in the cartilage of young adults are more observable. However, a discussion of the development of these cartilage lesions is necessary to determine how
9A
FIG. 9. A: Arthroscopic findings of case 3. Immediately after injury. No particular lesion can be seen on the cartilage of the medial facet of the patella. B: One year after the realignment operation. Arthroscopic findings reveal type III lesion of the articular cartilage.
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202
FIG. 10. An arthrogram of case 4. The arthrogram shows a localized cartilage defect at the medial side of the medial femoral condyle (arrow).
these lesions progress to the later stages. Would they always proceed, or would they heal naturally? Additionally, the relationship between the symptoms and the cartilage lesion must be discussed. We have found that the arthrogram is a useful method for identifying cartilage lesions. After an arthrogram is done, arthroscopy then is performed to diagnose the lesion more specifically. Mechanism of development of cartilage lesions Most of the patients in whom we found cartilage lesions in the femoral condyle played some sort of sport placing strong forces on the knee. Twenty percent of those cases are accompanied by injuries in the meniscus. However, it should not be concluded casually that it is the direct, vertical forces that damage the cartilage. We have observed that
FIG. 12. Arthroscopic findings of case 5. Type V lesion of the cartilage can be seen on the medial femoral condyle.
the majority of the lesions started in the outside part of the femoral condyle rather than in the weightbearing part. This indicates that abduction or adduction of the knee rather than direct stress is a factor in the injury: it is a shearing stress rather than a direct force that plays a crucial role. We also found instances in which cartilage lesions developed from the deep layers of the cartilage to the surface layers rather than the more common occurrence whereby the lesion begins in the surface layers and erodes to the deeper layers. In case 1 described above, dissection of the subchondral bone in the medial femoral condyle was observed in the radiograph, but no obvious tear was found on its covering cartilage surface. However, the cartilage was soft when touched, and the case was considered to be an early stage of osteochondritis dissecans. Based on the findings above, we 13A,B
FIG. 11. Arthroscopic findings of case 4. Type IV lesion of the cartilage can be seen on the medial femoral condyle.
Arthroscopy,
Vol. 7. No. 2, 1991
FIG. 13. A: Atrophy and fragmentation of the subchondral bone of the patella, 2 weeks after dislocation of the patella (arrow). B: Hypertrophy of the subchondral bone (arrow) in the same case, 2 years after dislocation.
CARTILAGE
LESIONS
concluded that the lesion had originated in the subchondral bone and had developed gradually to the cartilage surface. Case 3 had a fracture of the subchondral bone in the medial facet caused by dislocation of the patella. The patient complained of acute pain in the corresponding area. However, arthroscopy identilied only slight flaking on the surface of the cartilage. Therefore, we concluded that the external force first damaged the subchondral bone. On follow-up, the bone fracture gradually healed after the realignment operation on the patella. As the bone fracture healed, the pain disappeared. However, on the l-year folow-up, the lesion had developed to type III. We concluded that the shearing stress that injured the subchondral bone also damaged the fibril network that lies at the bottom of the cartilage close to the bone, right beyond the tide mark. This injury to the bottom layer probably spread toward the surface layers in time. No sign of healing of the lesion, at least macroscopically, was observed. Eleven percent (live joints in the patella and two in the femoral condyle) of the knees observed in this study followed this pattern of very slight or no damage to the cartilage surface when examined using arthroscopy but obvious injuries in the subchondral bone in the radiographs. In addition, live cases were observed to have bone hypertrophy after atrophy on the subchondral bone after repeated episodes of dislocation and subluxation of the patella (Fig. 13). This also may have originated from the small injuries in the subchondral bone. We assume the reason for the injuries in the deep layers is that the shearing stress that is applied onto the surface of the cartilage is highly viscoelastic. A previous experimental study we performed obtained the results that support this assumption (1). The relationship between the pain the patient reports and cartilage lesions is difficult to evaluate objectively because there are individual differences in sensitivity to pain and other subjective factors. Furthermore, the pain could be due to the synovitis caused by cartilage lesions rather than due to the cartilage lesions themselves. However, based on our observations and findings from the cases studied, we can say that in the cases of fibrillation or defect within the cartilage layers of the femoral condyle (cases 2 and 4), the patients complained of
IN KNEE
203
little pain. In constrast, in cases 1, 3, and 5, in which the lesions penetrated the subchondral bone, the patients experienced strong pain regardless of the severity of the lesions on the cartilage surface. We assume that this indicates that the pain is related more to the lesions of the subchondral bone than to the lesions within the cartilage. As in case 3, the pain gradually decreased and eventually disappeared as the dissected bone fracture was healed, in spite of the fact that the cartilage lesions had proceeded. CONCLUSION We analyzed the nature of cartilage lesions that are found frequently in adolescent knee joints based on the findings from arthroscopy, plain radiography, and arthrograms. We suggest that unnatural shearing stresses applied to the cartilage are closely related to the occurrence and development of cartilage lesions. In fact, in many cases joint instability accompanied the cartilage lesions, whether the lesions were on the patellofemoral joint or the tibiofemoral joint. We therefore would conclude that to prevent and treat cartilage lesions, it is crucial to remove the instability in the patellofemoral and tibiofemoral joint. REFERENCES 1. Imai N, Tomatsu T, Okamoto H, Nakamura Y. Clinical and roentgenological studies on malalignment disorders of the patello-femoral joint. Part III: lesions of the patellar cartilage and subchondral bone associated with patello-femoral malalignment. J Jpn Orthop Assoc 1989;63:1-17. 2. Bauer M, Jackson RW. Chondral lesions of the femoral condyles: a system of arthroscopic classification. Arrhroscopy 1988;4:72-80. 3. Dzioba RB. The classification and treatment of acute articular cartilage lesions. Arthroscopy 1988;4:72-80. 4. Fairbank JCT. Pvnsent PB. vanpoortvliet JA. Philhus H. Mechanical factors in the incidence of knee pain in adolescents and young adults. J Bone Joint Surg [Br] 1984;66:68!593. 5. Glowacki J. Cartilage and bone repair: experimental and clinical studies. Arthroscopy 1986;2:169-73. 6. Hopkinson WJ, Mitchell WA, Curl WW. Chondral fractures of the knee. Am J Sports Med 1085;13:309-12. 7. Johnson-Nurse C, Dandy DJ. Fracture separation of articular cartilage in the adult knee. J Bone Joint Surg [Br] 1985;67:42-3. 8. Minns RJ. Cartilage ulceration and shear fatigue fracture. Lancer 1976;1:907-8. 9. Repo RU, Finlay JB. Survival of articular cartilage after controlled impact. .J Bone Joint Surg [Am] 1977;59:106&76.
Arthroscopy,
Vol. 7, No. 2, 1991
