A comparison of muscle activation and knee mechanics during gait between patients with non-traumatic and post-traumatic knee osteoarthritis.

OBJECTIVE: The objective was to compare muscle activation and knee mechanics during gait between participants with non-traumatic knee osteoarthritis (OA), post-traumatic knee OA, and healthy adults. DESIGN: Participants with non-traumatic knee OA (n = 22), post-traumatic knee OA (n = 19), and healthy adults (n = 22) completed gait trials for this observational, cross-sectional study. Post-traumatic OA group had a history of traumatic anterior cruciate ligament (ACL) rupture. Surface electromyography (EMG) measured activation of seven lower extremity muscles. Motion capture cameras and force plates measured motion and force data. Principal component analysis (PCA) determined waveform characteristics (principal components) from EMG, knee angle, and knee external moment waveforms. Analysis of variance (ANOVA) examined group differences in principal component scores (PC-scores). Regression analyses examined if a variable that coded for OA group could predict PC-scores after accounting for disease severity, alignment, and lateral OA. RESULTS: There was lower gastrocnemius EMG amplitudes (P < 0.01; ANOVA) in the post-traumatic OA group compared to healthy group. Non-traumatic OA group had higher vastus lateralis, vastus medialis, and rectus femoris EMG compared to post-traumatic OA group (P = 0.01 to 0.04) in regression analyses. Also, non-traumatic OA group had higher and prolonged lateral hamstring EMG compared to healthy (P = 0.03; ANOVA) and post-traumatic OA (P = 0.04; regression) groups respectively. The non-traumatic OA group had lower knee extension (P < 0.05) and medial rotation (P < 0.05) moments than post-traumatic and healthy groups. CONCLUSIONS: Muscle activation and knee mechanics differed between participants with non-traumatic and post-traumatic knee OA and healthy adults. These OA subtypes had differences in disease characteristics that may impact disease progression.

Intra-articular dislocation of the patella: case report and literature review.

PURPOSE: To inform physicians treating sport injuries of a rare and unique form of patella dislocation, the horizontal intra-articular dislocation of the patella. CASE SUMMARY: A young male sustained a direct blow to the upper pole of the patella and came into the emergency room with a knee locked at 75 degrees of flexion. He had an irreducible dislocation of the patella in which the patella was displaced inferiorly, rotated 90 degrees, and locked into the intercondylar notch of the femur. DISCUSSION: This injury occurs most often in young men and usually requires open reduction. Literature review indicates patients presenting a knee near full extension have a better chance for successful closed reduction, possibly because of a lesser degree of patella entrapment in the intercondylar notch. RELEVANCE: Most physicians are unaware of this rare type of patella dislocation. It can, however, be recognized by its typical mechanism of injury and clinical features. Unlike the common lateral patella dislocation, on-site reduction is not possible. This injury requires closed and often open reduction under general anesthesia.

Peritalar dislocations in children.

Five patients with peritalar dislocations were identified in a search for injuries of the talus. We report the mechanism, management, and outcome of their injuries and compare and contrast the injuries with the same injury in adults. To our knowledge, our series is the only small series of this rare injury in children. Four of our 5 patients had acceptable results with respect to pain and gait. In two patients, the peritalar dislocation was missed, necessitating a delay in management because more attention is focused on obvious fractures, when they exist.

Diagnostic evaluation of patients with histiocytosis X.

The natural history of histiocytosis X was reviewed in 52 patients to identify the characteristics of patients with localized versus disseminated disease. Two categories of patients were identified. Older patients with solitary or multiple bone lesions constituted a low-risk group. This group had a high rate of development of new bone lesions (55% were asymptomatic) but an excellent prognosis. Patients with soft tissue involvement constituted a group at high risk for disease progression and organ dysfunction. These patients required a more extensive diagnostic workup and systemic treatment. A diagnostic algorithm is proposed to identify these two groups.