Paper cientific

1. ABSTRACT
Purpose. To assess the Insall-Salvati ratio in normal
Indian adults to determine its applicability and
the incidence of patella alta and baja in Indian
populations.
Method. 800 knees in 200 men and 200 women aged
18 to 50 (mean, 30) years were evaluated using lateral
radiographs. The knee was set in semi-flexion (30º) to
enable good visualisation of the patellar tendon and
its insertion into the tibia on radiographs. The length
of the patellar tendon (LT) over the length of the
patella (LP)—the Insall-Salvati ratio—was measured,
using a vernier caliper.
Results. The mean LT/LP ratio was 1.14 (standard
deviation, 0.18). Based on the 95% confidence
interval, the ratio was considered normal if within
±40%. The LT/LP ratio was significantly higher in
females than males (1.17 vs. 1.12, p<0.01). The cut-off
point of patella alta was significantly greater in our
Indian subjects than in western subjects (>1.5 vs. >1.2,
p<0.0001). In the present cohort, the frequencies of
Position of the patella in adults in central
India: evaluation of the Insall-Salvati ratio
Sachin Upadhyay, HKT Raza, Pranay Srivastava
Department of Orthopaedics, Netaji Subhas Chandra Bose Medical College Jabalpur, (MP), India
Address correspondence and reprint requests to: Dr Sachin Upadhyay, 622, “Poonam” Sneh Nagar, State Bank Colony Jabalpur
482002 MP, India. Email: drsachinupadhyay@gmail.com
Journal of Orthopaedic Surgery 2013;21(1):23-7
patella alta (ratio, >1.5) and patella baja (ratio, <0.7)
were 2.8% and 1%, respectively.
Conclusion. The use of the Insall-Salvati ratio to
determine the patellar position is less applicable to
Indian populations in which squatting, sitting cross-
legged, and kneeling are customs. We propose that
the normal range of the ratio for squatters among
Indian populations be 0.7 to 1.5.
Key words: patella; patellar ligament
INTRODUCTION
The patella is an integral component of the extensor
mechanism of the knee joint. It increases the efficiency
of the quadriceps muscle by increasing its leverage.1,2
It lengthens the extension moment arm throughout
the range of motion. The patellar height is an
imperative structural measurement.3
It is the length
of the patellar tendon (LT) over the length of the
patella (LP) and is termed the Insall-Salvati ratio.4
In
a study by Insall and Salvati,4
the mean LT/LP ratio
was 1.02 (standard deviation [SD], 0.13), and patella

2. 24 S Upadhyay et al. Journal of Orthopaedic Surgery
baja and patella alta were indicated when the ratio
were <0.80 and >1.20, respectively. This ratio remains
the same in almost all degrees of knee flexion.5
A high-riding patella (patella alta) may be
associated with recurrent lateral dislocation and
subluxation of the patella,6–9
chondromalacia
patellae,10–13
patellar ligament rupture and Sinding-
Larsen-Johansson disease,9,14
and patellar and
quadriceps tendonitis and Osgood-Schlatter
disease.15,16
A low-riding patella (patella baja) may
be associated with quadriceps tendon rupture,
neuromuscular disorders, achondroplasia, and
postoperative advancement of the tibial tuberosity.17–19
We assessed the Insall-Salvati ratio (LT/LP) in
normal Indian adults to determine its applicability
and the incidence of patella alta and baja in Indian
populations, in which squatting, sitting cross-legged,
and kneeling are customs.
MATERIALS AND METHODS
Between September 2005 and September 2006, 800
knees in 200 men and 200 women aged 18 to 50 (mean,
30) years were evaluated using lateral radiographs.
Those with a history of knee surgery, underlying knee
pathology, knee pain during walking or squatting,
or trauma in lower limbs were excluded. This study
was approved by our institutional review board, and
informed consent was obtained from each subject.
Radiographs of the knee were taken, with
the knee set in semi-flexion (30º) with the aid of a
goniometer. This enabled good visualisation of the
patellar tendon and its insertion into the tibia. The
X-ray was perpendicular to the film and centered
on the joint at a distance of 100 cm. A 0.5-mm-thick
lead sheet was placed over the genitalia to reduce the
scatter dose by a factor of 100.20
Measurements were made using a vernier caliper.
The LT was measured from its origin on the lower pole
of the patella to its insertion into the tibial tubercle. A
well-defined notch suggestive of the insertion point
was used as a benchmark if the tendon could not be
adequately visualised. The LP was measured from
the articular superior to the non-articular inferior
pole (Fig.).
Parametric values reported in the present and
previous studies were compared using the Student’s
t test. An alpha value of 0.05 was considered for the
level of significance. Data were verified for normal
distribution before parametric test of analysis.
RESULTS
The mean LT/LP ratio was 1.14 (SD, 0.18). Based on
the 95% confidence interval, the ratio was considered
normal if within ±40%. The cut-off point of patella
alta was significantly greater in our Indian subjects
than in western subjects (>1.5 vs. >1.2, p<0.0001).
The LT/LP ratio was significantly higher in females
than males (1.17 vs. 1.12, p<0.01, Table 1). In the
present cohort, the frequencies of patella alta (ratio,
>1.5) and patella baja (ratio, <0.7) were 2.8% and
1%, respectively (Table 2). The LT/LP ratio was
10% higher in our Indian subjects than in western
populations4,21–23
(p<0.0001, Table 3).
DISCUSSION
Patella alta and patella baja represent the 2 ends of the
scale of the LT/LP ratio. Anomalies in patella position
are associated with derangements of patellofemoral
function such as chondromalacia10–13
and recurrent
subluxation or dislocation of the patella.6–9
Lateral
patellar subluxation is coupled with diminished
lateralisation of the patella-femoral junction contact
area, which increases lateral patellofemoral junction
stress and results in patellofemoral osteoarthritis.24
Figure Measurements of the length of the patellar tendon
(LT) and the length of the patella (LP).
LP
LT

3. Vol. 21 No. 1, April 2013 Position of the patella in adults in central India 25
Realignment achieves satisfactory outcome in those
with mal-alignment or malposition of the patella.25
Shiftingthetendoninsertionbothmediallyanddistally
is important when performing a patellar tendon
transfer for patella subluxation.7,26,27
Patellofemoral
arthritis may result if the patellar tendon is rerouted
too far distally, as the articular surface of the patella
is forced against the femoral condyles. Patellar
tendon transfer (to restore the normal patellofemoral
relationship) should be performed only when the
height of the patella is clearly abnormal. Thus, this
demands a clear definition of the normal position of
the patella in the knee.
The insertion of patellar tendon is subject to
muscular traction. During growth of a bone, ligaments
and tendons migrate in different rates for different
insertions. The nearer the insertion to the extremity
of the bone, the greater is the migration.28,29
During
migration of the patellar tendon, its deeper layer is
constantly lengthened at the insertion site, whereas
its superficial layer slides over the surface of the tibial
tuberosity.30
In an experimental study,30
migration
of ligaments and tendons is due to the growth of
the periosteum dragging the insertions during its
stretching by the activity of the epiphyseal plates.
Squatting and sitting cross-legged are common
activities of daily living in Indian cultures. The Insall-
Salvati ratio is often restricted to chair-sitting western
populations and may not be generalised to others.
The patellar position is empirical for evaluation of
the anatomic alignment of the knee and anterior knee
pain.31,32
A patella alta may cause pain secondary to
patellar instability33–36
or chondromalacia patellae10–13
that results from abnormal patellofemoral junction
contact stress.37
Following knee trauma or surgery,38–40
particularly harvesting of a patellar tendon
autograft,17,18
progressive shortening of the patellar
tendon may lead to patella baja.10
Several techniques have been described for
radiological evaluation of the patellar height.5,41–45
The Insall-Salvati ratio4
is easy to calculate and
independent of the degree of knee flexion.5,23
The
normal ratio is 1.02±0.13; values >1.2 are suggestive
of patella alta and values <0.8 are suggestive of
patella baja.17,18
For the Blackburne-Peel method,44
the patellar ligament was not considered in assessing
the patellar height. Squatters have greater range
of knee flexion.46
The presence of the quadricipital
groove, which results from patellar ligament pressure
against the upper end of the tibia, makes projecting a
forward line along the tibial plateau difficult.46
The
Blackburne-Peel method gives different results for
squatters. Thus, grading the patellar level in relation
to the tibial plateau is not appropriate for assessing
the patellar position in squatters.
In the current study, the LT/LP ratio was
significantly greater in females than males (p<0.01),
which was consistent with findings of other
studies.47–50
We therefore disagreed with studies that
conclude the ratio to be independent of sex.4,21–23
The
lengths of the patella and the patellar ligament were
shorter in Indian females than males. For Indian
subjects, patella alta was indicated when the ratio
was >1.5, which was significantly greater than that
reported in other studies (p<0.0001).4,21,22
In a southern Chinese population, the position
of patella is 15 to 20% higher than that in western
populations.51
Apatella alta index of >3.4 is considered
Parameter Mean Standard deviation p Value
LT (cm) <0.0001
Male 5.16 0.96
Female 4.44 0.39
Both 4.80 0.67
LP (cm) <0.0001
Male 4.63 0.34
Female 3.80 0.31
Both 4.22 0.32
LT/LP ratio <0.01
Male 1.12 0.23
Female 1.17 0.13
Both 1.14 0.18
Table 1
Measurements of the ratio of the length of the patellar
tendon (LT) over the length of the patella (LP)
LT/LP ratio Frequency (%)
<0.8 12 (3)
0.8–1.0 140 (35)
1.0–1.2 170 (43)
1.2–1.4 53 (13)
>1.4 25 (6)
Study Mean±SD LT/LP ratio
Present study 1.14±0.18*
Insall and Salvati4
1.02±0.13
Schlenzta and Schwesinger21
1.00±0.14
Ahmed22
1.02±0.13
Theodore et al.23
1.00±0.2
Table 2
Distribution of subjects in terms of the ratio of the length of
the patellar tendon (LT) over the length of the patella (LP)
Table 3
Comparison of studies in terms of the ratio of the length of
the patellar tendon (LT) over the length of the patella (LP)
* p<0.0001, Student’s t test

4. 26 S Upadhyay et al. Journal of Orthopaedic Surgery
REFERENCES
1. Hohl M. Fractures of the patella. In: Fractures. Rockwood CA Jr, Green DP, editors. Philadelphia: JB Lippincott; 1975:1148–
56.
2. Perry J, Antonelli D, Ford W. Analysis of knee-joint forces during flexed-knee stance. J Bone Joint Surg Am 1975;57:961–7.
3. Kaufer H. Mechanical function of the patella. J Bone Joint Surg Am 1971;53:1551–60.
4. Insall J, Salvati E. Patella position in the normal knee joint. Radiology 1971;101:101–4.
5. Grelsamer RP, Meadows S. The modified Insall-Salvati ratio for assessment of patellar height. Clin Orthop Relat Res
1992;282:170–6.
6. Andersen PT. Congenital deformities of the knee joint in dislocation of the patella and achondroplasia. Acta Orthop Scand
1958;28:27–50.
7. Hauser ED. Total tendon transplant for slipping patella. A new operation for recurrent dislocation of the patella. Surg Gynec
Obstet 1938;66:199–214.
8. McKeever DC. Recurrent dislocation of the patella. Clin Orthop 1954;3:55–60.
9. Smillie IS. Injuries of the knee joint. 4th ed. Edinburgh: Livingstone; 1970.
10. Lancourt JE, Cristini JA. Patella alta and patella infera. Their etiological role in patellar dislocation, chondromalacia, and
apophysitis of the tibial tubercle. J Bone Joint Surg Am 1975;57:1112–5.
11. Insall J, Falvo KA, Wise DW. Chondromalacia patellae. A prospective study. J Bone Joint Surg Am 1976;58:1–8.
12. Karadimas JE, Piscopakis N, Syrmalis L. Patella alta and chondromalacia. Int Orthop 1981;5:247–9.
13. Bentley G, Dowd G. Current concepts of etiology and treatment of chondromalacia patellae. Clin Orthop Relat Res
1984;189:209–28.
14. Medlar RC, Lyne ED. Sinding-Larsen-Johansson disease. Its etiology and natural history. J Bone Joint Surg Am 1978;60:1113–
6.
15. Matava MJ. Patellar tendon ruptures. J Am Acad Orthop Surg 1996;4:287–96.
16. Aparicio G, Abril JC, Calvo E, Alvarez L. Radiologic study of patellar height in Osgood-Schlatter disease. J Pediatr Orthop
1997;17:63–6.
17. Noyes FR, Wojtys EM, Marshall MT. The early diagnosis and treatment of developmental patella infera syndrome. Clin
Orthop Relat Res 1991;265:241–52.
18. Tria AJ Jr, Alicea JA, Cody RP. Patella baja in anterior crutiate ligament reconstruction of the knee. Clin Orthop Relat Res
1994;299:229–34.
19. Kalichman L, Zhang Y, Niu J, Goggins J, Gale D, Felson DT, et al. The association between patellar alignment and
patellofemoral joint osteoarthritis features—an MRI study. Rheumatology (Oxford) 2007;46:1303–8.
20. Vaño E, Gonzalez L, Fernandez JM, Alfonso F, Macaya C. Occupational radiation doses in interventional cardiology: a 15-
year follow-up. Br J Radiol 2006;79:383–8.
21. Schlenzka D, Schwesinger G. The height of the patella: an anatomical study. Eur J Radiol 1990;11:19–21.
22. Ahmed AD. Radiological assessment of the patella position in the normal knee joint of adult Nigerians. West Afr J Med
1992;11:29–33.
23. Miller TT, Staron RB, Feldman F. Patellar height on sagittal MR imaging of the knee. AJR Am J Roentgenol 1996;167:339–41.
24. Hinterwimmer S, Gotthardt M, von Eisenhart-Rothe R, Sauerland S, Siebert M,Vogl T, et al. In vivo contact areas of the knee
in patients with patellar subluxation. J Biomech 2005;38:2095–101.
25. Insall JN. Intra-articular surgery for degenerative arthritis of the knee. A report of the work of the late K.H. Pridie. J Bone
Joint Surg Br 1967;49:211–28.
26. Hughston JC. Subluxation of the patella. J Bone Joint Surg Am 1968;50:1003–26.
27. Jones JB, Francis KC, Mahoney JR. Recurrent dislocating patella. A long-term follow-up study. Clin Orthop 1961;20:230–
40.
28. Grant PG, Buschang PH, Drolet DW. Positional relationships of structures attached to long bones during growth. Cross-
sectional studies. Acta Anat (Basel) 1978;102:378–84.
abnormal in these population.51
This might be due to
the constant stretching effect over the patellar tendon
during squatting, sitting cross-legged, and kneeling,
which are common activities in India, Japan, China,
South-East Asia, and the Middle East.28–30
One limitation of the current study was that it
lacked a cohort with pathological conditions of the
knee, particularly chondromalacia and dislocation
of the patella. Moreover, the LT/LP ratio was not
applicable in children, because their bones are mainly
cartilaginous and not clearly visible on radiographs.
The use of the Insall-Salvati ratio to determine
the patellar position is less applicable to Indian
populations in which squatting, sitting cross-legged,
and kneeling are customs. We propose that the
normal range of the ratio for squatters among Indian
populations be 0.7 to 1.5.
DISCLOSURE
No conflicts of interest were declared by the authors.

5. Vol. 21 No. 1, April 2013 Position of the patella in adults in central India 27
29. Grant PG, Hawes MR. Experimental modification of muscle migration in the rabbit. J Anat 1977;123:361–7.
30. Dorfl J. Migration of tendinous insertions. I. Cause and mechanism. J Anat 1980;131:179–95.
31. Luyckx T, Didden K,Vandenneucker H, Labey L, Innocenti B, Bellemans J. Is there a biomechanical explanation for anterior
knee pain in patients with patella alta? Influence of patellar height on patellofemoral contact force, contact area and
contact pressure. J Bone Joint Surg Br 2009;91:344–50.
32. Metin Cubuk S, Sindel M, Karaali K, Arslan AG, Akyildiz F, Ozkan O. Tibial tubercle position and patellar height as
indicators of malalignment in women with anterior knee pain. Clin Anat 2000;13:199–203.
33. Colvin AC, West RV. Patellar instability. J Bone Joint Surg Am 2008;90:2751–62.
34. Dandy DJ, Poirier H. Chondromalacia and the unstable patella. Acta Orthop Scand 1975;46:695–9.
35. Boden BP, Pearsall AW, Garrett WE Jr, Feagin JA Jr. Patellofemoral instability: evaluation and management. J Am Acad
Orthop Surg 1997;5:47–57.
36. Roberts CS. Anterior knee pain and patellar instability. J Bone Joint Surg Am 2006;88:1908.
37. Kannus PA. Long patellar tendon: radiographic sign of patellofemoral pain syndrome—a prospective study. Radiology
1992;185:859–63.
38. Morshed S, Ries MD. Patella infera after nonoperative treatment of a patellar fracture. A case report. J Bone Joint Surg Am
2002;84:1018–21.
39. Archibeck MJ, White RE Jr. What’s new in adult reconstructive knee surgery. J Bone Joint Surg Am 2002;84:1719–26.
40. Parvizi J, Hanssen AD, Spangehl MJ. Total knee arthroplasty following proximal tibial osteotomy: risk factors for failure. J
Bone Joint Surg Am 2004;86:474–9.
41. Boon-Itt SB. The normal position of the patella. AJR 1930;24:389–94.
42. Blumensaat C. Die lageabweichungen und verrenkungen der kniescheibe. Ergeb Chir Orthop 1938;31:149–223.
43. Jacobsen K, Bertheussen K, Gjerloff CC. Characteristics of the line of Blumensaat. An experimental analysis. Acta Orthop
Scand 1974;45:764–71.
44. Blackburne JS, Peel TE. A new method of measuring patellar height. J Bone Joint Surg Br 1977;59:241–2.
45. Egund N, Lundin A, Wallengren NO. The vertical position of the patella. A new radiographic method for routine use. Acta
Radiol 1988;29:555–8.
46. Kate BR, Robert SL. Some observations on the upper end of the tibia in squatters. J Anat 1965;99:137–41.
47. Marks KE, Bentley G. Patella alta and chondromalacia. J Bone Joint Surg Br 1978;60:71–3.
48. Norman O, Egund N, Ekelund L, Runow A. The vertical position of the patella. Acta Orthop Scand 1983;54:908–13.
49. Aglietti P, Insall JN, Cerulli G. Patellar pain and incongruence. I: Measurements of incongruence. Clin Orthop Relat Res
1983:176:217–24.
50. Dowd GS, Bentley G. Radiographic assessment in patellar instability and chondromalacia patellae. J Bone Joint Surg Br
1986;68:297–300.
51. Leung YF, Wai YL, Leung YC. Patella alta in southern China. A new method of measurement. Int Orthop 1996;20:305–10.