Prevalenceandsensitivityoftriggerpointsinlumbo-pelvic-hipmusclesinpatientswithpatellofemoralpainsyndrome

Patellofemoral pain syndrome (PFPS) is a common cause of anterior knee pain that primarily affects young women. While the exact cause remains unclear, researchers have increasingly recognized that problems in the lumbo-pelvic-hip region — the muscles of the lower back, pelvis, and hip — may contribute to this condition. Myofascial trigger points (MTrPs) are hyperirritable spots in muscles that can cause local pain and refer pain to other areas. They can impair muscle function, reduce strength, and alter movement patterns.

Previous research suggested that impaired proximal stability from the lumbo-pelvic-hip region might lead to PFPS, but no studies had systematically examined how common trigger points are across these muscles in people with PFPS compared to healthy individuals. Knowing which specific muscles harbor trigger points could help therapists target treatment more effectively rather than treating every muscle in this large region.

This study recruited 30 women with PFPS and 30 healthy women, all between 18 and 40 years old. The two groups were matched for age, height, and weight. A trained examiner who did not know which participants had PFPS assessed 14 muscles across three regions: lumbar muscles (internal oblique, erector spinae, quadratus lumborum), pelvic muscles (gluteus maximus, gluteus medius, gluteus minimus, piriformis), and hip muscles (tensor fascia lata, sartorius, rectus femoris, vastus medialis, vastus lateralis, semitendinosus, semimembranosus, biceps femoris, and hip adductors). The examiner identified trigger points by palpation using established criteria: finding a taut band, tenderness, local twitch response, referred pain, or spontaneous pain patterns.

After finding trigger points, the researcher used a pressure algometer to measure the pressure pain threshold — the amount of pressure needed before the participant felt pain — recording this in kg/cm². Statistical tests compared prevalence rates between groups and pressure pain thresholds.

The prevalence of trigger points was significantly higher in patients with PFPS for most muscles examined. In lumbar muscles, 80.0% of PFPS patients had trigger points in the internal oblique versus 33.0% of healthy women (p<0.001); 70.0% versus 26.7% in quadratus lumborum (p=0.001); and 76.7% versus 26.7% in erector spinae (p<0.001). In pelvic muscles, significant differences were found for gluteus maximus (60.0% vs 13.3%, p=0.006), gluteus medius (90.0% vs 56.7%, p=0.004), and piriformis (76.7% vs 43.3%, p=0.001), but not for gluteus minimus (93.3% vs 76.7%, p=0.071). In hip muscles, significant differences were found for tensor fascia lata (63.3% vs 23.3%, p=0.002), rectus femoris (76.7% vs 40.0%, p=0.004), sartorius (56.7% vs 30.0%, p=0.030), vastus medialis (66.7% vs 13.3%, p<0.001), vastus lateralis (76.7% vs 20.0%, p<0.001), semitendinosus and semimembranosus combined (90.0% vs 53.3%, p=0.002), and biceps femoris (86.7% vs 50.0%, p=0.002).

No significant difference was found for adductor muscles (96.7% vs 83.3%, p=0.085). Pressure pain thresholds were significantly lower in PFPS patients across all muscles tested, meaning they experienced pain with less pressure. For example, quadratus lumborum threshold was 1.39±0.86 kg/cm² in PFPS versus 2.92±1.46 in healthy participants (p<0.001); gluteus medius was 1.17±0.59 versus 2.61±1.20 (p<0.001); and vastus lateralis was 1.48±0.94 versus 3.36±1.41 (p<0.001).

This study provides evidence that trigger points in the lumbo-pelvic-hip region are more common and more sensitive in women with PFPS compared to healthy individuals. The findings suggest that therapists treating PFPS should consider addressing trigger points in proximal muscles, not just focusing on the knee itself. The gluteus minimus and adductor muscles appear to be less useful as primary targets since trigger points were equally common in both groups. The extremely high prevalence of trigger points in adductor muscles in both groups (96.7% and 83.3%) suggests this may be a common finding in women generally rather than specific to PFPS.

For patients, this means that knee pain may be connected to problems in the back, pelvis, and hip muscles, and comprehensive treatment addressing these areas may be beneficial. However, the study only included women, so these findings may not apply to men, and the cross-sectional design cannot determine whether trigger points cause PFPS, result from it, or share a common cause.