Osteoarthritis of the patella, lateral femoral condyle and posterior medial femoral condyle correlate with range of motion

KNEE

Osteoarthritis of the patella, lateral femoral condyle and posteriormedial femoral condyle correlate with range of motion

Takashi Suzuki • Sayaka Motojima •

Shu Saito • Takao Ishii • Keinosuke Ryu •

Junnosuke Ryu • Yasuaki Tokuhashi

Received: 25 October 2012 / Accepted: 15 April 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose The type of osteoarthritis and the degree of

severity which causes restriction of knee range of motion

(ROM) is still largely unknown. The objective of this study

was to analyse the location and the degree of cartilage

degeneration that affect knee range of motion and the

connection, if any, between femorotibial angle (FTA) and

knee ROM restriction.

Methods Four hundreds and fifty-six knees in 230 sub-

jects with knee osteoarthritis undergoing knee arthroplasty

were included. Articular surface was divided into eight

sections, and cartilage degeneration was evaluated macro-

scopically during the operation. Cartilage degeneration was

classified into four grades based on the degree of exposure

of subchondral bone. A Pearson correlation was conducted

between FTA and knee flexion angle to determine whether

high a degree of FTA caused knee flexion restriction.

A logistic regression analysis was also conducted to detect

the locations and levels of cartilage degeneration causing

knee flexion restriction.

Results No correlation was found between FTA and

flexion angle (r = -0.08). Flexion angle was not restricted

with increasing FTA. Logistic regression analysis showed

significant correlation between restricted knee ROM and

levels of knee cartilage degeneration in the patella (odds

ratio (OR) = 1.77; P = 0.01), the lateral femoral condyle

(OR = 1.62; P = 0.03) and the posterior medial femoral

condyle (OR = 1.80; P = 0.03).

Conclusion For clinical relevance, soft tissue release and

osteophyte resection around the patella, lateral femoral

condyle and posterior medial femoral condyle might be

indicated to obtain a higher degree of knee flexion angle.

Level of evidence Case–control study, Level III.

Keywords Knee � Osteoarthritis � Cartilage � Range of

motion

Introduction

Osteoarthritic change in the knee joint is a common con-

dition in the elderly population. Though knee pain is major

factor, restriction of range of motion (ROM) is also a sig-

nificantly unsatisfying condition for patients with knee

osteoarthritis (OA). Flexion angle was reported as the most

important factor for functional results following TKA [24].

Furthermore, several studies found that postoperative ROM

in TKA is most greatly affected by preoperative ROM [2, 7,

10, 12, 23]. It is believed that ROM restriction in the knee

occurs when there is knee deformity with cartilage degen-

eration on the knee joint surface. However, we sometimes

encounter patients who can flex their knee deeply, even

though they have end-stage knee osteoarthritis with severe

malalignment. This poor correlation between the degree of

OA based on radiographic evaluation and knee function led

to the question: ‘what type of osteoarthritis and what degree

of severity causes the restriction of knee ROM?’. Therefore,

it has been chosen to evaluate the severity of knee OA

macroscopically and analyse the correlation to knee ROM

prior to surgery. This study would be useful to predict the

range of knee motion before knee arthroplasty.

T. Suzuki (&) � S. Motojima � S. Saito � T. Ishii � K. Ryu �Y. Tokuhashi

Department of Orthopaedic Surgery, Nihon University

School of Medicine, 30-1 Oyaguchi Kamimachi, Itabashiku,

Tokyo 173-8610, Japan

e-mail: [email protected]

J. Ryu

Research Center, Nihon University, Tokyo, Japan

123

Knee Surg Sports Traumatol Arthrosc

DOI 10.1007/s00167-013-2508-x

The objective of this study was to reveal the factors

associated with knee ROM restriction in subjects suffering

from end-stage knee osteoarthritis. The hypothesis was that

knee ROM would not be affected by femorotibial angle

(FTA) and that characteristic OA lesions and high degrees

of severity would be correlated with restriction of knee

ROM.

Materials and methods

A total of 484 knees in 282 subjects (32 men and 250 women)

underwent TKA for knee osteoarthritis in our department

between August 2006 and February 2008. The indications for

surgery were patients with end-stage osteoarthritis with a

Kellgren and Lawrence (K and L) grading system of 3 or 4 and

who resisted conservative treatment for 6 months. Exclusion

criteria for this study included inflammatory arthropathies,

prior knee surgery such as osteotomy or arthroscopy, prior

infection and arthroplasty to treat a fracture. Valgus knees

(FTA \ 175�) were also excluded due to the possibility that

valgus knees might be caused by conditions other than pri-

mary osteoarthritis such as calcium pyrophosphate dihydrate

(CPPD) crystal deposition disease, rheumatoid arthritis or

charcot arthropathy. Cases of aggressive osteoarthritis

(FTA [ 200�) were also excluded due to the possibility of

Charcot’s arthropathy. The remaining 456 joints in 230

patients (26 men and 204 women) were included in this study.

All participants gave their informed consent to be part of the

study. The mean age of the subjects was 73.1 ± 7.6 years, and

TKA was performed on 230 right knees and 226 left knees. All

TKA were performed at the same institution. At the time of

surgery, the level of cartilage degeneration was evaluated

macroscopically. A longitudinal incision was made in the

anterior knee, and the articular capsule was incised at the

medial margin of the patella. Cartilage surface was investi-

gated after excising the meniscus, and medial and lateral

posterior condyles were observed on excised pieces following

osteotomy. Preoperatively, the FTA of both legs in the

standing position was measured on full-limb plain radio-

graphs, and the passive knee ROM was assessed using a

goniometer with the patient supine. Knee angle was defined as

the angle between the femoral long axis and the fibular long

axis. The femoral long axis was defined as the line connecting

the greater trochanter and the lateral epicondyle of the femur.

The fibular long axis was defined as the line connecting the

fibular head and the lateral malleolus. The measurement

accuracy of the goniometer was 1�.

The articular surface of the knee was divided into eight

sections: (1) patella, (2) patellar groove, (3) lateral femoral

condyle, (4) medial femoral condyle, (5) lateral tibial

condyle, (6) medial tibial condyle, (7) posterior lateral

femoral condyle and (8) posterior medial femoral condyle

(Fig. 1). Articular cartilage degeneration was classified into

four grades: Grade 0 (normal), Grade 1 (mild; localised

superficial ulceration on the articular cartilage), Grade 2

(moderate; deep ulceration with exposed subchondral bone,

less than 1 cm in diameter) and Grade 3 (severe; deep

ulceration with exposed subchondral bone, more than 1 cm

in diameter) (Fig. 2). The degree of cartilage degeneration

in each section was evaluated macroscopically by the

senior orthopaedic surgeons (T. S, S. S, T. I, K. R) par-

ticipating in the surgery.

Statistical analysis

Data are presented as the mean ± standard deviation.

A Pearson correlation coefficient was conducted between

FTA and knee flexion angle to determine the correlation

between high FTA and knee flexion angle restriction. To

evaluate which factors influenced knee flexion angle

restriction, subjects were divided into two groups: the

flexion angle restricted group (R group) and the non-

restricted, normal group (N group). The R group was

Fig. 1 Eight sections of knee articular cartilage undergoing TKA

Fig. 2 Classification of articular cartilage degeneration based on the

degree of exposure of subchondral bone


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defined as knees whose knee flexion angle was 100� or less,

while the knee flexion angle of the N group was more than

100�. A chi-square test was performed for comparison of

gender, and a Student’s t tests was performed for com-

parison of both age and FTA between the R group and the

N group.

Logistic regression analysis of selected variables (gen-

der, age, FTA, grade of cartilage degeneration in each

articular section) was performed to identify factors inde-

pendently associated with knee flexion angle restriction.

P \ 0.05 was adopted as the level of statistical signifi-

cance. Statistical software (SPSS ver. 20, Chicago, IL) was

used in the statistical analysis.

Results

The mean preoperative FTA of all knees was 187� ± 5�.

The mean preoperative extension angle was -7� ± 10�,

and the mean flexion angle was 116� ± 16�. The R group

consisted of knees with ROM of less than 100�, based on

the preoperative knee flexion angle. The number of knees

in each cartilage degeneration grade at each section is

shown in Table 1. No correlation was found in the Pearson

correlation coefficient between FTA and flexion angle

(r = -0.08) (Fig. 3). Flexion angle was not restricted with

increased FTA.

The mean preoperative FTA in the R group was

188� ± 5� compared with 187� ± 5� in the N group

(Table 2). No significant difference in gender, age or FTA

was observed between the R group and the N group. Logistic

regression analysis indicated that the predictors of knee

flexion angle restriction for OA patients were the levels of

knee cartilage degeneration in the patella (odds ratio (OR),

1.77; 95 % confidence interval (95 % CI), 1.14–2.74;

P = 0.010), the lateral femoral condyle (OR 1.62; 95 % CI

1.04–2.53; P = 0.034) and the posterior medial femoral

condyle (OR 1.80; 95 % CI 1.05–3.09; P = 0.032)

(Table 3). Gender, age, FTA and the levels of knee cartilage

degeneration in the patella groove, the medial femoral con-

dyle, the lateral tibial condyle, the medial tibial condyle and

the posterior lateral femoral condyle showed no significant

correlation with knee flexion angle restriction.

Table 1 Number of joints in each articular cartilage degenerative

grade

Grade

0

Grade

1

Grade

2

Grade

3

Total

Patella 7 130 239 80 456

Patella groove 9 96 249 102 456

Lateral femoral condyle 67 282 76 31 456

Medial femoral condyle 0 0 10 446 456

Lateral tibial condyle 87 302 53 14 456

Medial tibial condyle 0 4 63 389 456

Posterior lateral femoral

condyle

86 275 77 18 456

Posterior medial

femoral condyle

1 26 139 290 456

Fig. 3 Pearson correlation coefficient between FTA and knee flexion

angle

Table 2 Comparison between flexion angle restricted group (R

group) and non-restricted, normal group (N group)

R group (N = 91) N group (N = 365) P value

Gender

Male 4 (4.4 %) 41 (11.2 %) n.s

Female 87 (95.6 %) 324 (88.8 %)

Age 73.2 ± 6.9 73.7 ± 6.6 n.s

FTA 187.5 ± 4.9 187.2 ± 4.8 n.s

Table 3 Logistic regression analysis of factors influencing knee

flexion angle restriction

Risk factors P value OR (95 % CI)

Gender n.s.

Age n.s.

FTA n.s.

Patella 0.010 1.77 (1.14–2.74)

Patella groove n.s.

Lateral femoral condyle 0.034 1.62 (1.04–2.53)

Medial femoral condyle n.s.

Lateral tibial condyle n.s.

Medial tibial condyle n.s.

Posterior lateral femoral condyle n.s.

Posterior medial femoral condyle 0.032 1.80 (1.05–3.09)

OR odds ratio, 95 % CI 95 % confidence interval, n.s. no statistical

difference


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Discussion

The most important findings of this study was that the

restriction of knee flexion was significantly correlated with

progressive cartilage degeneration in the patella, the lateral

femoral condyle and the posterior medial femoral condyle,

but not with increasing FTA.

A macroscopic evaluation was used to determine the

size and lesion of cartilage degeneration because of the

difficulties involved in arthroscopic evaluation [19].

Several grading systems of cartilage degeneration of

osteoarthritis have been reported previously. Some of these

are grading systems based on histopathological structure

[13, 14, 18]. Others are grading scales based on macro-

scopic evaluation. Classifications for cartilage degenerative

change observed macroscopically were reported in studies

using cadaver patellae and acromioclavicular joints [21,

26]. However, colour and small degenerative changes may

differ between cadaver cartilage and human cartilage. In

the human knee joint, with regard to cartilage degeneration

observed macroscopically at the time of surgery for

osteoarthritis of the knee, Koshino and Machida [9]

reported a grading scale of nine levels. However, with such

a large number of grades, variations are likely to occur

depending on the observer. Therefore, we divided carti-

laginous degenerative change into four grades based on the

degree of subchondral bone exposure.

Using this grading scale, it was found that the most

severe levels of degenerative change occurred in the medial

femoral condyle and the medial tibial condyle. These

results were consistent with those reported previously [15,

16]. Cartilage degeneration in the posterior medial femoral

condyle was observed in many cases in this study even

though this site is not a loading surface, with 93 % of all

knees being classified as grade 2 or 3. This is a site which

does not contact the tibia when the knee is flexed at an

angle greater than 120� [6]. Description of osteoarthritis in

the posterior femoral condyle is relatively rare in the

existing literature. Ogino et al. [20] reported the appear-

ance of abnormal shadows in 22 % of posterior lateral

condyles and 8.6 % of posterior medial condyles in an

investigation of knee MRIs in 654 Americans. The inci-

dence of osteoarthritis in the posterior femoral condyle

may be greater in Asian populations due to traditional

squatting or kneeling movements, which engender more

opportunities for deep flexion. Nakagawa reported that the

tibia and femur lose contact and appear to be ‘hinging’ on

the posterior horns of the menisci in full flexion (162�) in

an MRI evaluation of normal knees [17]. The knee is

highly constrained at high flexion, which may be due in

part to the compression of posterior soft tissues (posterior

capsule, menisci, muscle, fat and skin) between the tibia

and the femur [11]. Therefore, squatting is reported as a

risk factor of progressive osteoarthritis [1, 3, 5]. Zang et al.

[28] compared Chinese subjects with subjects in the United

States and concluded that prolonged squatting may explain

why Chinese elderly subjects had such a high prevalence of

knee OA. Furthermore, a high level of posterior medial

femoral osteoarthritis may affect the accuracy of rotational

alignment of the femoral component in TKA. The posterior

condylar axis is often used to determine rotational align-

ment. When cartilage wear in the posterior medial condyle

is more than that in the lateral condyle, the result is likely

to be an alignment with a more external rotation [27]. In

TKA, surgeons should consider that cartilage wear in the

posterior medial condyle is often severe in end-stage knee

osteoarthritis. In our study, regarding degenerative carti-

lage change in the patella and patellar groove, grades 2 and

3 together accounted for 75 % of all knees. This rate was

slightly more than a previous report of adult human cada-

ver knees, which observed patellar OA in 63.7 % of all

subjects [8].

With respect to range of knee motion, it is generally

thought that the range of flexion in cases of knee osteoar-

thritis is restricted by a marked narrowing of the medial

joint space, which can be observed in AP radiographs. The

hypothesis of this study was that progressive knee osteo-

arthritis exhibiting a high degree of FTA would not always

result in restriction of knee flexion. The result of the

Pearson correlation coefficient confirmed that increasing

FTA was not correlated with knee ROM restriction. This

study demonstrated that the range of flexion in the knee

joint decreased with progressive cartilage deterioration in

the patella, the lateral femoral condyle and the posterior

medial femoral condyle. Accordingly, the present results

suggest that in the knee joint, flexion angle does not

decrease with progressive cartilage degeneration in the

medial aspects of the femorotibial joint only, but that range

of flexion is restricted and contracted when cartilage

degeneration reaches the posterior femoral condyle or lat-

eral femorotibial joint or patellofemoral joint. The reason

for this may be that severe osteoarthritis is characterised by

the presence of osteophytes and contraction of soft tissue.

Ozdemir et al. [22] reported that significant correlations

were found between knee ROM and the size, location and

direction of osteophytes in an evaluation of osteophytes in

OA knees using a standing radiographic AP view. We were

unable to evaluate the characteristics of osteophytes in this

study because it proved to be too difficult to assess the size,

shape and location of osteophytes macroscopically or

radiographically. If one cause of knee flexion restriction is

the presence of osteophytes and the contracture of soft

tissue around the patella, lateral femoral condyle and

posterior medial femoral condyle, resection of osteophytes

and soft tissue release in the affected areas may result in

increased knee flexion angle. These procedures will be


123

necessary in surgical manipulation or knee arthroplasty to

obtain the highest degree of flexion. In the future, addi-

tional studies evaluating the relationship between the type

or location of osteophytes and range of knee motion should

be conducted.

This study has several potential limitations: (1) Patients

in our study were in the end stages of knee osteoarthritis

which required TKA. Nearly all patients had high levels of

cartilage degeneration in the medial components. The

degeneration was grade 3 in 96 % of all medial femoral

condyles. Therefore, there was a lack of data on mild and/

or moderate cases. (2) This research focuses solely on

knees of Japanese patients. Habitual squatting is common

in Japanese culture. As previously described, such squat-

ting may affect cartilage degeneration, especially in the

posterior femoral condyle. In the future, more research

involving other ethnic groups should be conducted. (3)

BMI data were not analysed in our logistic regression

analysis. The circumference of the thigh and lower leg may

be an influence on ROM. Further research including such

data will be also necessary in the future. (4) This research

was conducted with FTA in a standing AP view. Stress

radiography and the Rosenberg view are both more sensi-

tive in assessing knee osteoarthritis [4, 25]. However, knee

radiography in the standing AP view is a general practice

and is still widely used for knee osteoarthritis patients.

Research using these more sensitive radiographic assess-

ments will be of great value in future studies. With con-

tinued research, we believe that the exact mechanism of

knee range restriction as it applies to osteoarthritis of the

knee will be clarified. Furthermore, such research will

allow surgeons to deduce with greater accuracy the loca-

tions in which degenerative cartilage change exists by

measuring the maximum flexion angle. Such data are

highly useful for surgeons when they choose to perform

unicompartmental knee arthroplasty and high tibial

osteotomy.

For clinical relevance, OA is likely to exist in the

patella, the lateral femoral condyle and the posterior medial

femoral condyle in knee OA patients with knee flexion

restriction. Surgeons should be aware of this fact and select

optional soft tissue release or osteophyte resection in the

affected areas to obtain a higher degree of knee flexion

angle following TKA.

Conclusion

Progressive cartilage degeneration in the patella, the lateral

femoral condyle and the posterior medial femoral condyle

led to restricted knee flexion. However, increasing FTA

was not correlated with knee ROM.

Acknowledgments The authors gratefully acknowledge Nakashima

Medical Co., Ltd. No benefits in any form have been received or will

be received from any commercial party related directly or indirectly

to the subject of this article.

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Osteoarthritis of the patella, lateral femoral condyle and posterior medial femoral condyle correlate with range of motion