Patients with knee osteoarthritis (OA) were reported to have quadriceps weakness, and impaired proprioception, both related to pain and swelling. It is unclear whether pain alone a causal factor to above findings over the knee joint. The purpose of this study was to assess the effects of knee pain alone on the quadriceps strength, proprioception and dynamic balance in subjects with bilateral knee OA without joint swelling. Fourty females with mean age of 68.3 years were involved in this cross-sectional study. The inclusion criteria were bilateral knee OA without joint swelling, with a visual analogue pain scale difference (> 1) between each knee. Patients all underwent assessment of the isokinetic strength of knee muscles, knee proprioceptive acuity, and dynamic balance. Patients’ more painful knee had weaker isokinetic quadriceps strength than less painful knee at both 60 °/s and 180 °/s (p = 0.01, p = 0.01, respectively). There were no differences in proprioceptive acuity between both knees in all three knee positions. Meanwhile, there was a significant difference in the dynamic balance index measurement between both knees (more painful versus less painful: 3.88 ± 1.15 vs. 3.30 ± 1.00, p = 0.01). Quadriceps strength was associated with dynamic balance stability (60 °/s, r = − 0.578, p < 0.01; 180 °/s, r = − 0.439, p < 0.01). For patients with knee OA, the more painful knee was associated with weaker quadriceps and poor balance ability. To improve lower limb function and balance stability of the older persons having knee OA, physicians should take the optimal pain management strategy.

[Purpose] After an anterior cruciate ligament injury and subsequent reconstruction, quadriceps muscle weakness and disruption of proprioceptive function are common. The purpose of this study was to examine the effects of a 4 weeks preoperative exercise intervention on knee strength power and function post-surgery. [Subjects and Methods] Eighty male patients (27.8±5.7 age), scheduled for reconstruction surgery, were randomly assigned to two groups, the preoperative exercise group (n=40) and a no preoperative exercise group (n=40). The preoperative exercise group participated in a 4-week preoperative and 12-week post-operative programs, while the no preoperative exercise group participated only in the 12-week postoperative exercise program. Isokinetic measured of quadriceps strength were obtained at 4 weeks before and 3 months after surgery. [Results] The knee extensor strength deficits measured at 60°/s and 180°/s was significantly lower in the preoperative exercise group compared with the no preoperative exercise group. At 3 months after surgery, the extensor strength deficit was 28.5±9.0% at 60°/sec and 23.3±9.0% at 180°/sec in the preoperative exercise group, whereas the no preoperative exercise group showed extensor strength deficits of 36.5±10.7% and 27.9±12.6% at 60°/sec and 180°/sec, respectively. The preoperative exercise group demonstrated significant improvement the single-leg hop distance. [Conclusion] Four week preoperative exercise may produce many positive effects post reconstruction surgery, including faster recovery of knee extensor strength and function, as measured by single-leg hop ability.

This study aimed to exam the isokinetic shoulder rotator strength of professional volleyball athletes, by playing positions. This cross-sectional study included a total of 49 healthy male professional volleyball players. We measured the isokinetic strength of the external rotator (ER) and internal rotator (IR) muscles and compared the dominant and non-dominant shoulders at angular speeds of 60°/s and 180°/s. In ER, all positions of players had similar strength between the dominant shoulder and non-dominant shoulders. Conversely, all playing positions except libero had stronger strength in dominant shoulder than that in the non-dominant shoulder. The ER/IR ratio in the dominant shoulder was significantly lower only for the attacker (outside hitter and opposite) at 60°/s and 180°/s (P < 0.0001; P = 0.0028 respectively) and blocker at 60°/s (P = 0.0273) when compared with non-dominant shoulder. Furthermore, the attacker had a lower ER/IR ratio in the dominant shoulder than setter and libero at 60°/s and 180°/s. For elite volleyball players without injury, the dominant shoulder had a higher strength of internal rotation, causing the relative muscle imbalance than the non-dominant shoulder, especially for the attacker and blocker positions. Training program should be individualized for each playing position to improve the imbalanced shoulder.

Quadriceps strength is critical for patients with anterior cruciate ligament (ACL) reconstruction; however, little is known about the relationship between preoperative quadriceps strength deficit and postoperative subjective knee functions. The study aimed to investigate the relationship between preoperative quadriceps strength and postoperative knee function in patients after ACL reconstruction. Seventy-five male patients with primary ACL reconstruction surgery with hamstring autografts between 2014 and 2017 were included. An isokinetic dynamometer assessed quadriceps strength while self-reported knee functions were measured by the International Knee Documentation Committee (IKDC) and Lysholm scores at baseline and 1 year after surgery. The three identified groups (Q1–Q3) were classified according to the preoperative quadriceps muscle strength deficit. Q1 were patients with < 25% quadriceps muscle strength deficit, Q2 showed a 25–45% deficit, and Q3 included those with a deficit > 45%. We compared knee functions between the three groups and examined the associations between preoperative variables and functional knee outcomes. The preoperative quadriceps muscle strength deficit had a negative association with the knee functional scores at 1 year follow-up including the IKDC score (r_s = − 0.397, p = 0.005) and the Lysholm score (r_s = − 0.454, p < 0.001), but not other factors. Furthermore, only the Q1 group, with < 25% deficit in preoperative quadriceps muscle strength, showed a significant correlation in postoperative IKDC score (r = − 0.462, p = 0.030), and Lysholm score (r = − 0.446, p = 0.038). Preoperative quadriceps muscle strength deficit had a significant negative relationship with postoperative function at 1 year following ACL reconstruction.

Comparing to primary surgery, revision ACL reconstruction is more technically demanding and has a higher failure rate. Theoretically, rehabilitation can improve knee function after ACL reconstruction surgery. This study aimed to compare knee stability, strength, and function between primary and revision ACL reconstructed knees. 40 primary and 40 revision ACL reconstruction surgeries were included between April 2013 and May 2016. Patients with revision surgery had a higher anteroposterior translation comparing those with primary reconstruction (median laxity, 2.0 mm vs. 3.0 mm, p = 0.0022). No differences were noted in knee extensor at 60°/sec or 180°/sec (p = 0.308, p = 0.931, respectively) or in flexor muscle strength at 60°/sec or 180°/sec between primary and revision ACL reconstruction knees (p = 0.091, p = 0.343, respectively). There were also no significant differences between functional scores including IKDC score and Lysholm score in primary versus revision surgeries at 12th months after index operation (p = 0.154, p = 0.324, respectively). In conclusion, despite having higher anteroposterior instability, patients with revision ACL reconstruction can have non-inferior outcomes in isokinetic knee strength and function compared to those with primary ACL reconstruction after proper rehabilitation.