A comparison of isokinetic muscle strength in patients with chondromalacia patella: a cross-sectional study.

Objective: Chondromalacia patella (CMP), which is one of the most common causes of anterior knee pain in young adults, is often accompanied by reflex inhibition of the quadriceps muscle. In this respect, a significant correlation between isokinetic parameters and knee muscle strengths would be expected. We hypothesized that an isokinetic dynamometer, which objectively evaluates muscle strength, may be an important guide in detecting muscle weakness in new-onset CMP and determining early treatment strategies.

Patients And Methods: A total of 113 participants (mean age 30.33 ± 6.96 years, min: 18, max: 44) were recruited and divided into two groups, thus a CMP group (n=48) and a control group (n=65). The symptom duration of the CMP group and the demographic characteristics of all participants were recorded. Knee flexion and extension muscle strengths were measured at angular velocities of 60°/s and 180°/s [Knee extension Peak Torque at 60°/s (PTE60), Knee flexion Peak Torque at 60°/s (PTF60), Knee extension Peak Torque at 180°/s (PTE180), Knee flexion Peak at 180°/s (PTF180) respectively] (five sets) using an isokinetic dynamometer. We also recorded the total work done in flexion and extension (TWDF and TWDE). A modified MRI staging system based on the Outerbridge arthroscopy system was used to stage CMP. Isokinetic dynamometric parameters were compared between CMP patients and healthy volunteers.

Results: 59 healthy volunteers (90.8%) were right-side dominant and 6 (9.2%) left-side dominant. 33 CMP patients (68.8%) were right-side dominant, and 15 (31.3%) left-side dominant. 20 (41.7%) CMP patients were classified as Stage 1, 20 (41.7%) as Stage 2, and 8 (16.7%) as Stage 3. All the PTF60, PTE60, PTF180, and PTE180 values were significantly lower in the CMP group than in healthy controls (all p < 0.05). CMP symptom duration ≥ 6 months was associated with significantly lower knee muscle strength than with symptom duration < 6 months (p < 0.05). Also, a statistically negative correlation was found between MRI stages and PTE60 values (p < 0.05).

Conclusions: In conclusion, our findings show that the isokinetic dynamometer reveals muscle weakness in CMP patients, and weakness in isokinetic parameters was negatively correlated with symptom duration and MRI stages. Isokinetic knee muscle strength testing, together with other functional tools, enables the assessment of muscle weakness and early rehabilitation planning for patients with CMP.