Research Article Correlation Between the Cartilage Angle of the Superior Part of the Femoral Trochlear Groove Measured in US and the Anterior Knee Pain
by Zbigniew Czyrny*
Private Practice, Consultant Enel-Sport, ul. Łazienkowska 3, Warszawa, Poland
*Corresponding Author: Czyrny Z, Private Practice, Consultant Enel-Sport, ul. Łazienkowska 3, Warszawa, Poland, zbigniew. czyrny@wp.pl,; czyrny.pl
Received Date: 03 January 2026
Accepted Date: 09 January 2026
Published Date: 12 January 2026
Citation: Czyrny Z (2026) Correlation Between the Cartilage Angle of the Superior Part of the Femoral Trochlear Groove Measured in US and the Anterior Knee Pain. Arch Surg 6: 133 DOI: 10.29011/3066-2559.000133
Summary
Aim of the Study: The aim of the study was assesment of the correlation between the cartilage angle of the upper max. 5mm of the femoral groove assesed in US and the pain of the the anterior knee assesed clinically. Bony angle was assesed by the way to see what is the difference between both.
Materials and Methods: 162 patients were enrolled in the study. 78 (48%) men and 84 (52%) women. Mediana of the mans age was 35 years (IQR: 24 - 45), mediana for the womens age: 38 (IQR: 26 - 54).The cartilaginous and the bony angle of the upper part (max 5mm) of the femoral groove were measured by US and the data from interviews and physical examination were analyzed for the presence of typical patello-femoral pain symptoms.
From the obtained data it is stated that statistically important number of patients had less frequently pain of the Patello-Femoral Joint (PFJ) with the cartilage groove angle below 160⁰. Above that angle the number of painful knees increases with statistical importance and above 170⁰ there is hihg propability of patellar luxation at some point of life.
Conclusions: The study indicates a high correlation between only one parameter of the Patello-Femoral Joint (PFJ) and anterior knee pain. It is both the strength and the weakness of it. If a single parameter gives statistically important angle treshold in 162 measurements that means it is a valuable tool for evaluation of the PFJ’s future. On the other hand there are combinations of many factors, of which the most important is the patellar height [1].
Keywords: Femoral Groove; Patello-Femoral Joint; US
Introduction
The femoral groove and its dysplasia is currently evaluated based on Dejour’s work on lateral x-ray of the knee [2]. The groove is not directly measured as an angle but as the depth of the groove at its mid-lower part. The norm is approx 130⁰. Author proposes criteria of correlation between the upper groove angle and anterior knee pain based on the angle of the femoral groove measured in US at its highest part (approx 5mm from the cartilage upper margin).
Aim of the study
The aim of the study was assesment of the correlation between the cartilage angle of the upper max. 5mm of the femoral groove asessed in US and the pain of the the anterior knee assesed clinically. Bony angle was assesed by the way to see what is the difference between both.
Materials and Methods
There were 162 patients/knees in the study: 78 (48 %) men and 84 (52%) women. Mediana of the men age was 35years (IQR: 24 - 45), mediana of the women age: 38years (IQR: 26 - 54). A cartilaginous and the bony groove angle were measured by US and the analyzed by a clinical data from the interview and the examination.
Results
The results show that there are statistically much less knees with pain when the cartilage angle of the upper femoral groove is below 160⁰. Above this value the number of patients with pain statistically importantly rises and above 170⁰ there is high possibility of patellar luxation (Tables 1-5, Figures 1,2).
There are two statistical options
- Seek the cut-off angle values for pain
- Seek the cut-off angle values for no pain
The first option seems more natural as we usually search for the disease not the lack of it. Upper groove angle as a predictor of pain. The study results show that the higher value of the groove angle the higher propability of pain.
For the angle 173⁰ - sensitivity 16 %, specificity 100 %
For the angle 161⁰ - sensitivity 37 %, specificity 90 %
For the angle 146⁰ - sensitivity 87 %, specificity 30 %
For the angle 137,4⁰ - sensitivity 100 %, specificity 5 %
|
median (IQR) |
|
|
Cartilage angle |
152.8 (146.5 - 159,9) |
|
Bone angle |
144.9 (139.0 - 152,5) |
Table 1: The groove angles in the whole group.
|
men |
women |
p |
|
|
median (IQR) |
median (IQR) |
||
|
Cartilage angle |
153.9 (147.4 - 160.1) |
151.7 (145.8 - 158.0) |
0.248 |
|
Bone angle |
144.4 (137.9 - 151.0) |
145.0 (139.4 - 153.2) |
0.546 |
Table 2: Median of the angles with the division into genders.
|
pain, n=62 |
No pain, n=100 |
p |
|
|
median (IQR) |
median (IQR) |
||
|
Cartilage angle |
157.6 (150.5 - 167.2) |
150. 5 (144,9 - 156.5) |
< 0.001 |
|
Bone angle |
149.4 (142.0 - 156.5) |
142.9 (136.3 - 149.5) |
< 0.001 |
Table 3: Median of the angles for the knees with and without pain of the anterior knee.
The values of both groove angles differ with a statistical importance in the group with and without pain.
|
Cartilage angle |
No pain |
pain |
all (raw) |
|
< 140⁰ |
11 (92 %) |
1(2%) |
12 |
|
140⁰-160⁰ |
76 (68 %) |
36 (32 %) |
112 |
|
>160⁰ |
13 (34 %) |
25 (66 %) |
38 |
|
all (column) |
100 |
62 |
162 |
Table 4: The spread of pain/no pain in the three cartilage angle segments.
Figure 1: Median cartilage groove angle.
Figure 2: Median bony groove angle.
|
Angle |
Pain |
No pain |
TRUE |
TRUE |
FALSE |
TRUE |
sensitivity |
specificity |
|
value |
positive |
negative |
negative |
negative |
||||
|
194.1 |
1 |
0 |
1 |
0 |
61 |
100 |
0.016 |
1 |
|
190.3 |
1 |
0 |
2 |
0 |
60 |
100 |
0.032 |
1 |
|
186.5 |
1 |
0 |
3 |
0 |
59 |
100 |
0.048 |
1 |
|
178.8 |
1 |
0 |
4 |
0 |
58 |
100 |
0.065 |
1 |
|
178.2 |
1 |
0 |
5 |
0 |
57 |
100 |
0.081 |
1 |
|
177.7 |
1 |
0 |
6 |
0 |
56 |
100 |
0.097 |
1 |
|
177.5 |
1 |
0 |
7 |
0 |
55 |
100 |
0.113 |
1 |
|
173.7 |
1 |
0 |
8 |
0 |
54 |
100 |
0.129 |
1 |
|
173.4 |
1 |
0 |
9 |
0 |
53 |
100 |
0.145 |
1 |
|
173 |
1 |
0 |
10 |
0 |
52 |
100 |
0.161 |
1 |
|
170.7 |
0 |
1 |
10 |
1 |
52 |
99 |
0.161 |
0.99 |
|
170.2 |
1 |
0 |
11 |
1 |
51 |
99 |
0.177 |
0.99 |
|
170.1 |
1 |
0 |
12 |
1 |
50 |
99 |
0.194 |
0.99 |
|
169.4 |
1 |
0 |
13 |
1 |
49 |
99 |
0.210 |
0.99 |
|
168.3 |
1 |
0 |
14 |
1 |
48 |
99 |
0.226 |
0.99 |
|
168 |
1 |
0 |
15 |
1 |
47 |
99 |
0.242 |
0.99 |
|
167.2 |
1 |
0 |
16 |
1 |
46 |
99 |
0.258 |
0.99 |
|
166.5 |
0 |
1 |
16 |
2 |
46 |
98 |
0.258 |
0.98 |
|
166.4 |
0 |
1 |
16 |
3 |
46 |
97 |
0.258 |
0.970 |
|
166.2 |
1 |
1 |
17 |
4 |
45 |
96 |
0.274 |
0.960 |
|
166 |
1 |
0 |
18 |
4 |
44 |
96 |
0.290 |
0.960 |
|
165.7 |
0 |
1 |
18 |
5 |
44 |
95 |
0.290 |
0.950 |
|
164.8 |
0 |
1 |
18 |
6 |
44 |
94 |
0.290 |
0.940 |
|
164.7 |
1 |
0 |
19 |
6 |
43 |
94 |
0.306 |
0.940 |
|
164.6 |
1 |
0 |
20 |
6 |
42 |
94 |
0.323 |
0.940 |
|
163.7 |
0 |
1 |
20 |
7 |
42 |
93 |
0.323 |
0.930 |
|
162.4 |
1 |
0 |
21 |
7 |
41 |
93 |
0.339 |
0.930 |
|
162.2 |
0 |
1 |
21 |
8 |
41 |
92 |
0.339 |
0.920 |
|
161.9 |
1 |
0 |
22 |
8 |
40 |
92 |
0.355 |
0.920 |
|
161.3 |
0 |
1 |
22 |
9 |
40 |
91 |
0.355 |
0.910 |
|
161.2 |
0 |
1 |
22 |
10 |
40 |
90 |
0.355 |
0.900 |
|
161 |
1 |
0 |
23 |
10 |
39 |
90 |
0.371 |
0.900 |
|
160.7 |
1 |
2 |
24 |
12 |
38 |
88 |
0.387 |
0.880 |
|
160.2 |
1 |
0 |
25 |
12 |
37 |
88 |
0.403 |
0.880 |
|
160.1 |
0 |
1 |
25 |
13 |
37 |
87 |
0.403 |
0.870 |
|
160 |
0 |
1 |
25 |
14 |
37 |
86 |
0.403 |
0.860 |
|
159.9 |
0 |
2 |
25 |
16 |
37 |
84 |
0.403 |
0.840 |
|
159.5 |
1 |
0 |
26 |
16 |
36 |
84 |
0.419 |
0.840 |
|
159.1 |
1 |
0 |
27 |
16 |
35 |
84 |
0.435 |
0.840 |
|
158.9 |
0 |
2 |
27 |
18 |
35 |
82 |
0.435 |
0.820 |
|
158.6 |
0 |
1 |
27 |
19 |
35 |
81 |
0.435 |
0.810 |
|
158.1 |
1 |
1 |
28 |
20 |
34 |
80 |
0.452 |
0.800 |
|
157.9 |
1 |
0 |
29 |
20 |
33 |
80 |
0.468 |
0.800 |
|
157.8 |
1 |
0 |
30 |
20 |
32 |
80 |
0.484 |
0.800 |
|
157.6 |
1 |
1 |
31 |
21 |
31 |
79 |
0.500 |
0.790 |
|
157.5 |
1 |
0 |
32 |
21 |
30 |
79 |
0.516 |
0.790 |
|
157.1 |
1 |
0 |
33 |
21 |
29 |
79 |
0.532 |
0.790 |
|
157 |
0 |
1 |
33 |
22 |
29 |
78 |
0.532 |
0.780 |
|
156.8 |
0 |
2 |
33 |
24 |
29 |
76 |
0.532 |
0.760 |
|
156.7 |
0 |
1 |
33 |
25 |
29 |
75 |
0.532 |
0.750 |
|
156.2 |
0 |
1 |
33 |
26 |
29 |
74 |
0.532 |
0.740 |
|
156 |
0 |
1 |
33 |
27 |
29 |
73 |
0.532 |
0.730 |
|
155.8 |
0 |
1 |
33 |
28 |
29 |
72 |
0.532 |
0.720 |
|
155.5 |
0 |
1 |
33 |
29 |
29 |
71 |
0.532 |
0.710 |
|
155.4 |
0 |
1 |
33 |
30 |
29 |
70 |
0.532 |
0.700 |
|
155.3 |
0 |
1 |
33 |
31 |
29 |
69 |
0.532 |
0.690 |
|
155.2 |
1 |
0 |
35 |
31 |
27 |
69 |
0.565 |
0.690 |
|
155.1 |
0 |
1 |
35 |
32 |
27 |
68 |
0.565 |
0.680 |
|
154.6 |
1 |
0 |
36 |
32 |
26 |
68 |
0.581 |
0.680 |
|
154.5 |
1 |
1 |
37 |
33 |
25 |
67 |
0.597 |
0.670 |
|
154.1 |
1 |
1 |
39 |
34 |
23 |
66 |
0.629 |
0.660 |
|
154 |
1 |
0 |
40 |
34 |
22 |
66 |
0.645 |
0.660 |
|
153.6 |
1 |
0 |
41 |
34 |
21 |
66 |
0.661 |
0.660 |
|
153.5 |
0 |
1 |
41 |
35 |
21 |
65 |
0.661 |
0.650 |
|
153.4 |
1 |
0 |
42 |
35 |
20 |
65 |
0.677 |
0.650 |
|
153.2 |
1 |
0 |
43 |
35 |
19 |
65 |
0.694 |
0.650 |
|
153.1 |
1 |
0 |
44 |
35 |
18 |
65 |
0.710 |
0.650 |
|
152.8 |
0 |
2 |
44 |
37 |
18 |
63 |
0.710 |
0.630 |
|
152.7 |
0 |
1 |
44 |
38 |
18 |
62 |
0.710 |
0.620 |
|
152.1 |
0 |
1 |
44 |
39 |
18 |
61 |
0.710 |
0.610 |
|
151.9 |
0 |
1 |
44 |
40 |
18 |
60 |
0.710 |
0.600 |
|
151.7 |
0 |
2 |
44 |
42 |
18 |
58 |
0.710 |
0.580 |
|
151.6 |
0 |
2 |
44 |
44 |
18 |
56 |
0.710 |
0.560 |
|
151 |
0 |
1 |
44 |
45 |
18 |
55 |
0.710 |
0.550 |
|
150.9 |
1 |
2 |
45 |
47 |
17 |
53 |
0.726 |
0.530 |
|
150.8 |
1 |
0 |
46 |
47 |
16 |
53 |
0.742 |
0.530 |
|
150.7 |
0 |
1 |
46 |
48 |
16 |
52 |
0.742 |
0.520 |
|
150.5 |
1 |
2 |
47 |
50 |
15 |
50 |
0.758 |
0.500 |
|
150.4 |
0 |
1 |
47 |
51 |
15 |
49 |
0.758 |
0.490 |
|
150.3 |
0 |
3 |
47 |
54 |
15 |
46 |
0.758 |
0.460 |
|
150.2 |
0 |
1 |
47 |
55 |
15 |
45 |
0.758 |
0.450 |
|
150 |
0 |
1 |
47 |
56 |
15 |
44 |
0.758 |
0.440 |
|
149.9 |
1 |
0 |
48 |
56 |
14 |
44 |
0.774 |
0.440 |
|
149.8 |
0 |
1 |
48 |
57 |
14 |
43 |
0.774 |
0.430 |
|
149.7 |
1 |
0 |
49 |
57 |
13 |
43 |
0.790 |
0.430 |
|
149.1 |
0 |
1 |
49 |
58 |
13 |
42 |
0.790 |
0.420 |
|
148.8 |
0 |
1 |
49 |
59 |
13 |
41 |
0.790 |
0.410 |
|
148.7 |
1 |
1 |
50 |
60 |
12 |
40 |
0.806 |
0.400 |
|
148.5 |
1 |
0 |
51 |
60 |
11 |
40 |
0.823 |
0.400 |
|
148.2 |
0 |
1 |
51 |
61 |
11 |
39 |
0.823 |
0.390 |
|
148.1 |
0 |
1 |
51 |
62 |
11 |
38 |
0.823 |
0.380 |
|
147.8 |
0 |
1 |
51 |
63 |
11 |
37 |
0.823 |
0.370 |
|
147.6 |
0 |
2 |
51 |
65 |
11 |
35 |
0.823 |
0.350 |
|
147.4 |
0 |
1 |
51 |
66 |
11 |
34 |
0.823 |
0.340 |
|
147.3 |
0 |
1 |
51 |
67 |
11 |
33 |
0.823 |
0.330 |
|
146.6 |
1 |
0 |
53 |
67 |
9 |
33 |
0.855 |
0.330 |
|
146.5 |
0 |
2 |
53 |
69 |
9 |
31 |
0.855 |
0.310 |
|
146 |
1 |
0 |
54 |
69 |
8 |
31 |
0.871 |
0.310 |
|
145.9 |
0 |
1 |
54 |
70 |
8 |
30 |
0.871 |
0.300 |
|
145.8 |
1 |
0 |
55 |
70 |
7 |
30 |
0.887 |
0.300 |
|
145.7 |
1 |
0 |
57 |
70 |
5 |
30 |
0.919 |
0.300 |
|
145.6 |
0 |
1 |
57 |
71 |
5 |
29 |
0.919 |
0.290 |
|
145.2 |
0 |
1 |
57 |
72 |
5 |
28 |
0.919 |
0.280 |
|
145.1 |
0 |
2 |
57 |
74 |
5 |
26 |
0.919 |
0.260 |
|
145 |
0 |
1 |
57 |
75 |
5 |
25 |
0.919 |
0.250 |
|
144.8 |
0 |
2 |
57 |
77 |
5 |
23 |
0.919 |
0.230 |
|
144.7 |
1 |
0 |
58 |
77 |
4 |
23 |
0.935 |
0.230 |
|
144.5 |
0 |
1 |
58 |
78 |
4 |
22 |
0.935 |
0.220 |
|
144.3 |
0 |
2 |
58 |
80 |
4 |
20 |
0.935 |
0.200 |
|
144.2 |
0 |
1 |
58 |
81 |
4 |
19 |
0.935 |
0.190 |
|
143 |
0 |
1 |
58 |
82 |
4 |
18 |
0.935 |
0.180 |
|
142.9 |
1 |
1 |
59 |
83 |
3 |
17 |
0.952 |
0.170 |
|
142.5 |
1 |
0 |
60 |
83 |
2 |
17 |
0.968 |
0.170 |
|
142.3 |
1 |
0 |
61 |
83 |
1 |
17 |
0.984 |
0.170 |
|
142.2 |
0 |
1 |
61 |
84 |
1 |
16 |
0.984 |
0.160 |
|
141.8 |
0 |
1 |
61 |
85 |
1 |
15 |
0.984 |
0.150 |
|
141.6 |
0 |
1 |
61 |
86 |
1 |
14 |
0.984 |
0.140 |
|
140.8 |
0 |
1 |
61 |
87 |
1 |
13 |
0.984 |
0.130 |
|
140.5 |
0 |
1 |
61 |
88 |
1 |
12 |
0.984 |
0.120 |
|
140.2 |
0 |
1 |
61 |
89 |
1 |
11 |
0.984 |
0.110 |
|
139.9 |
0 |
1 |
61 |
90 |
1 |
10 |
0.984 |
0.100 |
|
139.2 |
0 |
1 |
61 |
91 |
1 |
9 |
0.984 |
0.090 |
|
139.1 |
0 |
2 |
61 |
93 |
1 |
7 |
0.984 |
0.070 |
|
137.9 |
0 |
1 |
61 |
94 |
1 |
6 |
0.984 |
0.060 |
|
137.8 |
0 |
1 |
61 |
95 |
1 |
5 |
0.984 |
0.050 |
|
137.4 |
1 |
0 |
62 |
95 |
0 |
5 |
1.000 |
0.050 |
|
135.3 |
0 |
1 |
62 |
96 |
0 |
4 |
1.000 |
0.040 |
|
134.4 |
0 |
1 |
62 |
97 |
0 |
3 |
1.000 |
0.030 |
|
133.1 |
0 |
1 |
62 |
98 |
0 |
2 |
1.000 |
0.020 |
|
129.8 |
0 |
1 |
62 |
99 |
0 |
1 |
1.000 |
0.010 |
|
127.1 |
0 |
1 |
62 |
100 |
0 |
0 |
1.000 |
0.000 |
Table 5: Statistics for all knees.
Upper groove angle below 140⁰ (Figures 3,4) means patellar hyperstability but in this material it doesn’t show that those patients are prone to develop pain if the anterior knee. In fact it’s the opposite. Patellas in the deep groove are less movable mediallateral than in the groove >140⁰. This means that PFJ problems start with unstable patella not a hyperstable one.
Figure 3: Transverse US scans over the upper femoral groove with angles below 140⁰. A very good prognosis for the knee.
Figure 4: Transverse US scans over the upper femoral groove with angles of 140⁰-160⁰. A very good prognosis for the knee. This is the angle range of most patients.
Patella in a danger of luxation has a groove above 170⁰ (Figure 5). All three patients from the study who had an episode of patellar luxation had upper groove angle above 170⁰. If the upper femoral groove angle is high and that means it could have over 180⁰ (flat or even convex) there is no bony stabilization of patella even if the patellar height is normal or even low.
Figure 5: Transverse US scans over the upper femoral groove with angles of over 160⁰. A bad/uncertain prognosis for the knee. The lowest image without a measurement as it is plain flat.
Conclusions
The study indicates a high correlation between only one parameter of the patello-femoral joint (PFJ) and anterior knee pain. It is both the strength and the weakness of it. If a single parameter gives statistically important angle treshold in 162 measurements that means it is a valuable tool for evaluation of the PFJ’s future. On the other hand there are combinations of many factors, of which the most important is the patellar height [1]. Three patients with patellar luxation in history had upper femoral cartilage groove angle >170°. So it seems important to use this parameter as one of most important features of the patello-femoral joint. The femoral groove angle can also be measured in MRI ans CT and the angle is sometimes the only clue to the knee problems.
Reference
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