Individuals with Patellofemoral Pain Have Reduced Hip Flexibility

Patellofemoral pain (PFP) syndrome (aka chondromalacia patella or runner’s knee) is a common musculoskeletal condition that occurs in running and jumping athletes. It is generally found in people who have degenerative joint disease (osteoarthritis) of the articular surfaces of the patella and/or femur (underside of the patella and/or intercondylar groove of the femur), and It presents with anterior knee pain, aggravated by physical activities. There is still no general agreement on just one clear aetiology. Some of the possible causes include biomechanical factors including excessive lateral tracking of the patella in the intercondylar groove, mal-alignment of the foot, genu valgum, poor movement control, overload and overuse, muscle imbalance, neuromuscular factors, previous trauma, and articular cartilage problems.

Several recent studies focussed on the hip joint and its potential role in patellofemoral pain.

Hip vs Knee Strengthening Study

A 2015 study showed that six weeks of hip or knee strengthening protocols produced improvements in PFP syndrome, including both function and strength.

The study was a single-blind randomized controlled trial conducted at four clinical research laboratories (one in Canada and four in the US). A total of 199 physically active individuals with PFP were recruited. The subjects were randomized into either a hip-focused or a knee-focused muscle-strengthening treatment program. Participants met with their respective athletic trainer up to 3 times per week over a 6-week period for exercise progression.

Primary variables were self-reported visual analog scale and Anterior Knee Pain Scale measures, which were conducted weekly. Secondary variables were muscle strength and core endurance measured at baseline and at 6 weeks.

The outcomes showed that, in terms of pain, compared with baseline, both the visual analog scale and the Anterior Knee Pain Scale improved for patients with PFP syndrome in both the HIP and KNEE protocols. Nevertheless, the visual analog scale scores for those in the HIP protocol were reduced 1 week earlier than in the KNEE group.

In terms of strength, both groups increased in strength, but those in the HIP protocol gained more in hip abductor and hip extensor strength, and posterior core endurance compared with the KNEE group.

The authors concluded that both the HIP and KNEE rehabilitation protocols produced improvements in PFP syndrome, function, and strength over 6 weeks. Although outcomes were similar, the HIP protocol resulted in earlier resolution of pain and greater overall gains in strength compared with the KNEE protocol.

Hip Flexibility Study

Now, a study published in the March 2017 edition of Clinical Journal of Sport Medicine examined differences in hip flexibility before and after a 6-week muscle-strengthening program between those with patellofemoral pain (PFP) and healthy controls.

The study used the same data as the above 2015 study, except that this study included data of 38 subjects without PFP as a healthy control. The healthy control subjects were also randomised to either a hip or knee strengthening exercise treatment.

In this study, the main outcome measures were flexibility-passive goniometry for the following ranges of motion (measured in joint angle degrees)

• hip adduction (HADD)
• hip external rotation (HER)
• hip internal rotation (HIR)
• total hip rotation (HROT)
• hip extension (HEXT)

The results showed that subjects with patellofemoral pain were less flexible than controls in every direction except HEXT regardless of treatment outcome or time.

Specifically, subjects with PFP who successfully completed the treatment program (n = 153) had 65%, 25%, 18%, and 12% LESS HADD, HER, HROT, and HIR ranges of motion (ROMs), respectively, compared to healthy controls.

Meanwhile, patellofemoral pain subjects who did not successfully complete the strengthening program (n = 41) had 134%, 31%, 22%, and 13% LESS HADD, HER, HROT, and HIR ROMs, respectively, than healthy controls.

All subjects (those with PFP syndrome who completed or did not complete the strengthening program, and healthy controls) increased their HIR, HROT, and HEXT ROMs when compared at pre-test to post-test, but by fewer than 2 degrees.

The authors concluded that individuals with PFP had less hip flexibility than controls regardless of treatment outcome or time. After the 6-week muscle strengthening program, and regardless of treatment success, PFP and control subjects experienced a small but clinically insignificant improvement in hip flexibility.

The authors further added that Hip ROM should be considered as a targeted area of focus in a rehabilitation program for physically active individuals with PFP.