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Knee range of motion (ROM) is an important indicator of knee function. Outside the clinical setting, patients may not be able to accurately assess knee ROM, which may impair recovery following trauma or surgery. This study aims to validate a smartphone mobile application developed to measure knee ROM compared to visual and goniometer ROM measurements. A knee ROM Android mobile application was developed to measure knee ROM. Patients ≥ 18 years old presenting to an orthopaedic clinic with native knee complaints were approached to participate. Knee ROM was measured bilaterally by an arthroplasty-trained surgeon using (1) vision, (2) goniometer, and (3) the mobile application. Measurements were compared in flexion and extension using a one-way analysis of variance with post hoc Tukey test (alpha = 0.05). Eighty-four knee ROM measurements (40 left, 44 right) were obtained in 47 patients. Median Kellgren-Lawrence grade from available radiographs was grade 3. In flexion, mobile application (117.6 ± 14.7 degrees) measurements were not significantly different from visual (116.1 ± 13.6 degrees) or goniometer (116.2 ± 13.6 degrees) measurements. In extension, mobile application (4.8 ± 7.3 degrees) measurements were significantly different from visual (1.9 ± 4.1 degrees) measurements on post hoc analysis ( p  < 0.01), while no differences were present compared to goniometer (3.1 ± 5.8 degrees) measurements. Our study found that a mobile application for evaluating knee ROM was noninferior to goniometer-based measurements performed by an arthroplasty-trained surgeon. Future studies will investigate this application's utility in (1) remote patient care, (2) accelerating recovery during rehabilitation, (3) detecting early postoperative complications including arthrofibrosis, and (4) adding additional functionalities to the application to provide more detail-oriented descriptive analyses of patient knee function., Competing Interests: None declared., (Thieme. All rights reserved.)

Objective: To evaluate whether knee contact force and knee pain are different between continuous and interval walking exercise in patients with knee osteoarthritis (OA)., Methods: Twenty seven patients with unilateral symptomatic knee OA completed two separate walking exercise sessions on a treadmill at 1.3m/s on two different days: 1) a continuous 45min walking exercise session, and 2) three 15min bouts of walking exercise separated by 1h rest periods for a total of 45min of exercise in an interval format. Estimated knee contact forces using the OpenSim software and knee pain were evaluated at baseline (1st minute of walking) and after every 15min between the continuous and interval walking conditions., Results: A significant increase from baseline was observed in peak knee contact force during the weight-acceptance phase of gait after 30 and 45min of walking, irrespective of the walking exercise condition. Additionally, whereas continuous walking resulted in an increase in knee pain, interval walking did not lead to increased knee pain., Conclusion: Walking exercise durations of 30min or greater may lead to undesirable knee joint loading in patients with knee OA, while performing the same volume of exercise in multiple bouts as opposed to one continuous bout may be beneficial for limiting knee pain., (Copyright © 2017. Published by Elsevier B.V.)

The incidence of patella baja in total knee arthroplasty (TKA) revisions for aseptic and septic causes is not well defined. We retrospectively reviewed 101 mobile-bearing TKA revisions performed between 2003 and 2009. Aseptic (n=67) and septic (n=34) revisions were compared for patella baja. A nonarticulating spacer was used as the initial treatment for infected cases. The Insall-Salvati ratio was radiographically measured before surgery (preexplant for septic revisions) and at latest follow-up (postreplant for septic revisions). Mean (SD) Insall-Salvati ratio did not differ between groups before surgery, 1.00 (0.25) for aseptic and 0.96 (0.22) for septic, but differed significantly after surgery, 0.99 (0.23) for aseptic and 0.77 (0.24) for septic. After correcting for preoperative patellar height, there was a statistically significant postoperative difference between aseptic cases, 1.09 (0.19), and septic cases, 0.82 (0.21). There was also a significant difference in mean (SD) postoperative range of motion (ROM) between aseptic cases, 108.0° (20.7°), and septic cases, 92.2° (34.6°), and decreased ROM between cases with patella baja, 95.1° (31.6°) and cases without patella baja, 106.8° (23.6°). TKA revisions done for septic causes using a nonarticulating spacer resulted in a higher incidence of patella baja and decreased ROM.

Background: To evaluate knee joint contact mechanics and kinematics during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability., Methods: Forty-three subjects, 11 with medial compartment knee osteoarthritis and self-reported instability (unstable), 7 with medial compartment knee osteoarthritis but no reports of instability (stable), and 25 without knee osteoarthritis or instability (control) underwent Dynamic Stereo X-ray analysis during a downhill gait task on a treadmill., Findings: The medial compartment contact point excursions were longer in the unstable group compared to the stable (P=0.046) and the control groups (P=0.016). The peak medial compartment contact point velocity was also greater for the unstable group compared to the stable (P=0.047) and control groups (P=0.022). Additionally, the unstable group demonstrated a coupled movement pattern of knee extension and external rotation after heel contact which was different than the coupled motion of knee flexion and internal rotation demonstrated by stable and control groups., Interpretation: Our findings suggest that knee joint contact mechanics and kinematics are altered during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. The observed longer medial compartment contact point excursions and higher velocities represent objective signs of mechanical instability that may place the arthritic knee joint at increased risk for disease progression. Further research is indicated to explore the clinical relevance of altered contact mechanics and kinematics during other common daily activities and to assess the efficacy of rehabilitation programs to improve altered joint biomechanics in knee osteoarthritis patients with self-reported instability., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional decline in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear., Methods: Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait., Findings: Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P<0.01), while the total abduction/adduction range of motion was increased (P<0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P<0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait., Interpretations: The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: Prosthetic joint infection is an uncommon but serious complication of total knee arthroplasty (TKA). Control of infection after TKA is not always possible, and the resolution of infection may require an above-knee amputation (AKA)., Questions/purposes: The purpose of this study was to determine the etiology of AKA and the functional outcomes of AKA after infected TKA., Methods: We retrospectively reviewed 35 patients who underwent AKA after an infected TKA. The amputations were performed an average of 6 years (range, 21 days to 24 years) after primary TKA. There were 19 females and 16 males with a mean age of 62 years (range, 26-88 years). Patient demographic information, comorbidities, surgical treatments, cultures, and culture sensitivities were recorded. Complications and functional status, including SF-12 and activities of daily living questionnaires, after AKA were also studied. The minimum followup was 7 months (mean, 39 months; range, 7-96 months)., Results: Two patients died secondary to cardiac arrest and 13 more died during the followup period of unrelated causes. Nine patients required irrigation and débridement for nonhealing wounds after AKA and two patients had repeat AKA for bony overgrowth. Of the 14 patients fitted for prostheses, eight were functionally independent outside of the home. Patients fitted with a prosthesis had higher mean activities of daily living scores (58 versus 38) and also tended to be younger with fewer comorbidities than those who were not fitted with a prosthesis., Conclusions: We found low functional status in living patients with an AKA after infection with only half of the patients walking after AKA., Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.