Chondromalacia Patella among Military Recruits with Anterior Knee Pain: Prevalence and Association with Patellofemoral Malalignment

Abstract

Background: The aim of this study was to investigate the frequency of chondromalacia patella (CMP) and to evaluate its relation with trochlear morphometric and patellofemoral alignment measurements as well as with edema in superolateral region of Hoffa's fat pad (SHFP) in military recruits with anterior knee pain (AKP).

Materials and methods: Knee magnetic resonance imaging examinations of 288 military recruits with AKP were retrospectively evaluated. Patellar cartilage lesions were graded using modified Noyes system. Quantitative measurements of trochlear morphology (sulcus angle, trochlear sulcus depth, and lateral trochlear inclination [LTI]) and patellofemoral alignment (patellar translation [PT], lateral patellofemoral angle (LPA), Insall-Salvati index, and tibial tuberosity-trochlear groove distance) were made. The SHFP region was assessed for the presence of edema. Mean values of measurements in knees with and without CMP and in knees with early and advanced stage CMP were compared.

Results: We found CMP in 169 (58.7%) patients. Patients with CMP demonstrated a significantly greater sulcus angle (P = 0.012), smaller LTI (P = 0.004), greater PT (P = 0.01), smaller LPA (P = 0.036), greater Insall-Salvati ratio (P = 0.034), and higher incidence of SHFP edema (P = 0.001) compared to those without CMP. While none of the measurements were associated with the severity of cartilage damage, the incidence of SHFP edema was significantly correlated with the severity of CMP (P = 0.001).

Conclusion: CMP is a common disorder among military recruits with AKP. Patellofemoral malalignment is an important contributory factor in the development of CMP, and the presence of edema in SHFP may be a strong indicator of underlying severe CMP in this population.

Keywords: Chondromalacia patella; magnetic resonance imaging; patellofemoral joint; trochlear morphology.

Figure 1

Axial proton density weighted, fat-suppressed magnetic resonance images showing patellar cartilage lesions according to modified Noyes system. (a) Grade 1, (b) Grade 2, (c) Grade 3, and (d) Grade 4, cartilage changes are seen

Figure 2

Axial proton density weighted, fat-suppressed magnetic resonance imaging sections demonstrating the methods of determining trochlear measurements. (a) Trochlear sulcus angle. (b) Trochlear depth. (c) Lateral trochlear inclination

Figure 3

Axial (a and b), and sagittal (c) proton density weighted, fat-suppressed magnetic resonance imaging sections demonstrating the methods of determining patellofemoral alignment measurements. (a) Patellar translation. (b) Lateral patellofemoral angle. (c) Insall-Salvati ratio

Figure 4

Axial magnetic resonance imaging images at 3 cm above the tibiofemoral joint cleft (a) and through tibial tuberosity (b), and a coronal magnetic resonance imaging section (c) demonstrating the tibial tuberosity to trochlear groove distance measurement method

Figure 5

Sagittal (a and c) and axial (b and d) magnetic resonance images showing superolateral Hoffa's fat pad. a and b show normal fat signal (red arrows) in this area. In another patient's knee, there is increased signal (blue arrows) consistent with edema (c and d)