Association Between Physical Tests and Patients-Reported Outcomes in Athletes Performing Exercise Therapy for Patellar Tendinopathy: A Secondary Analysis of the JUMPER Study

Abstract

Background: Physical tests are commonly used in patellar tendinopathy to aid the clinical diagnosis, assess the prognosis, and monitor treatment. However, it is still unknown whether these physical measures are associated with patient-reported outcomes after exercise therapy.

Purpose: To identify the prognostic value of baseline physical test results and to determine the association between physical response after exercise therapy and clinical improvement over 24 weeks.

Study design: Case-control study; Level of evidence, 3.

Methods: This study recruited 76 consecutive athletes with patellar tendinopathy who were randomized to 2 different programs of exercise therapy for 24 weeks. Athletes underwent a range of physical tests before and during exercise therapy (12 and 24 weeks), including isometric muscle strength (quadriceps and hip abductors), muscle flexibility (quadriceps, hamstrings, soleus, and gastrocnemius), vertical jump height, and visual analog scale (VAS) scores by palpation, after 3 jump trials, and after single-leg squat (VAS-SLS). The Victorian Institute of Sports Assessment-Patella (VISA-P) questionnaire was used as the primary patient-reported outcome. Linear mixed-effect models were used to assess the prognostic value of baseline physical tests. The change in VISA-P score was further dichotomized into clinical responsiveness (≥14 points) and nonresponsiveness (<14 points). Multiple linear and logistic regression models were performed to evaluate associations between physical response and clinical improvement.

Results: Of the 76 included patients, 67 (88%) had complete follow-ups. The estimated mean VISA-P score increased by 23 points (95% CI, 19-28 points) after 24 weeks. No association was found between any baseline physical test results and a 24-week change in VISA-P score (all P_interaction > .2, using the likelihood ratio test). Improvement in VAS-SLS after exercise therapy was not associated with VISA-P improvement after adjustment (β = -1.76; P = .01; Bonferroni-corrected P = .10; R² = 36.3%). No associations were found between changes in other physical test results and clinical improvement (all P > .05).

Conclusion: In patients with patellar tendinopathy, physical test results including strength and flexibility in the lower limb, jump performance, and pain levels during pain-provoking tests were not identified as prognostic factors for patient-reported outcomes after exercise therapy. Similarly, changes in physical test results were not associated with changes in patient-reported outcomes after adjustments. These results do not support using physical test results to estimate prognosis or monitor treatment response.

Registration: NCT02938143 (ClinicalTrials.gov identifier).

Keywords: VISA-P; exercise rehabilitation; overuse injury; physical functional performance; prognosis.

Figure 1.

(A) Maximal isometric voluntary contraction (MVC) of the quadriceps muscles was measured with the participant in a seated position on the examination table with both legs hanging over the edge of the table. A fixation band and a plurimeter were used to perform the measurements. Participants were asked to have a straight back and to put both hands on their shoulders. Once the knee flexion angle was at 60° (measured by a plurimeter), the fixation belt was fixed at this position. Participants were asked to put pressure on the dynamometer by contracting their quadriceps while the examiner stabilized the dynamometer. (B) MVC of the hip abductor muscles was measured with the participant in a side-lying position, with the contralateral leg at 90° of flexion. The participant was asked to support his or her head with one hand, and the other hand was used to grasp the edge of the examination table. The participants was asked to put pressure on the dynamometer by contracting the hip abductor muscles against the resistance of the examiner. (C) Quadriceps flexibility was conducted in a prone position. The examiner identified the maximum passive knee flexion angle. Anterior pelvic tilt motion was prevented. (D) Hamstring flexibility was performed in a supine position. The maximum active knee extension angle was dictated by the patient, with a fully extended contralateral leg. (E and F) Participants were asked to lunge in front of the wall. The maximum ankle dorsiflexion range of motion was measured. Soleus flexibility was measured when participants were asked to lunge the knee and touch the wall as far as possible without lifting the heel. The gastrocnemius flexibility was measured by straightening the knee with the ankle at the maximum dorsiflexion angle, still without lifting the heel. (G and H) Participants were asked to wear an adjusted belt connected by a piece of rope before performing 3 trials of the vertical jump. Then, they were asked to land on the mat and report their visual analog scale (VAS) score for maximum pain afterward. The height (cm) was shown on the screen of the device. (I) The single-leg squat was conducted on a 25° decline board. Participants were asked to keep an upright trunk and squat up to 90° of knee flexion. Their VAS score for maximum pain was reported afterward. (J) Tenderness by palpation was assessed using patellar tilting and palpation with the other hand.

Figure 2.

Flow diagram. VISA-P, Victorian Institute of Sports Assessment–Patella.

Figure 3.

(A-J) Visualization of the prognostic value of baseline physical test results. The prognostic value of each baseline physical test result on the progression of the Victorian Institute of Sports Assessment–Patella (VISA-P) score (0-100 points) over 24 weeks is depicted by dichotomizing baseline physical test results into low and high levels using the median value for illustration purposes. Plots represent the progression of VISA-P scores over 24 weeks by different levels of baseline physical test results. Dots represent marginal estimated means by mixed-effect model without time × physical test interaction. Shaded areas represent the 95% CIs after the Bonferroni correction. There was not a significant difference in the rate of increase in VISA-P between low and high baseline physical test results. VAS, visual analog scale; VAS-palpation, VAS by palpation test; VAS-SLS, VAS after single-leg squat test; VAS-3-jumps, VAS after 3 jump trials.

Figure 4.

The association between change in physical test results and clinical improvement. (A and B) The associations between the change in the Victorian Institute of Sports Assessment–Patella (ΔVISA-P) score and the change in the visual analog scale single-leg squat test (ΔVAS-SLS) score were evaluated by linear regression models using imputed and complete-case data, adjusted with study arms, sex, body mass index, age, and previous symptom duration, sports activity, and baseline VISA-P scores. Lines represent regression lines. Shaded areas represent the 95% CIs. The P values are not adjusted by Bonferroni correction. (C) Forest plots of multivariable logistic regression to make an association between the change in physical test results and the occurrence of clinical responsiveness (change of VISA-P score ≥14 points) using imputed and complete-case data sets. OR, odds ratio; VAS-palpation, VAS by palpation test; VAS-3-jumps, VAS after 3 jump trials.