Objective: With the remarkable advances in diagnostic ultrasound equipment, there is a growing need for ultrasound diagnosis of muscle and soft tissue injuries in sports injuries. Among these, hamstring strains are often difficult to treat and require early and accurate diagnosis. Injuries to the proximal part of the hamstring often take a long time to heal. For this reason, the diagnosis of proximal hamstring injuries is extremely important. The structure of the origin tendon is characteristic, and it is a complex in which the semitendinosus muscle (ST) of the medial hamstring and the long head of the biceps femoris muscle (BFLH) of the lateral hamstring share a conjoint tendon (CT). On the other hand, the semimembranosus muscle (SM) attaches to the ischial tuberosity independently. In this study, we created a classification of injury sites focusing on the origin tendon, and investigated the distribution of injury location, relationship to the player’s position, and the detection rate of ultrasound diagnosis. Material and Methods: We used ultrasound and MRI to diagnose 52 university men’s rugby players who had suffered a hamstring strain for the first time and investigated the distribution of the injured areas. We performed an ultrasound scan as the initial diagnosis and used MRI as a final diagnostic tool. A classification focusing on the origin of the muscle was created. First of all, it was divided into two types: the BFLH-ST complex type, which originates in the CT, and the SM type, which originates in the SM tendon. We also classified BFLH-ST complex damage, including CT damage, as Type I, a BFLH injury without CT injury as Type II, and a ST injury without CT injury as Type III. We then investigated the distribution of the injury location. The degree of ultrasound detection in each injury type was evaluated in three grades. The frequency of BFLH complex and SM injuries was investigated in players who played the forward (FW) and back (BK) positions. Results: The distribution was 40 limbs (77%) for BFLH-ST complex injury type and 12 limbs (23%) for SM injury type. In the BFLH complex type,19 limbs which met the Type I classification criteria for CT tear, 19 limbs met the Type II, and 2 limbs met the Type III. FWs had a higher incidence of SM injuries and BKs had a higher incidence of BFLH-ST complex injuries. With regard to the detection of muscle injuries via ultrasound, a high rate of detection was possible, except for a slight injury to the myofascial junction of the BFLH. Discussion: In terms of the distribution, the BFLH-ST complex, which shares the same origin tendon (i.e. CT), had a higher frequency of muscle tears than the SM. In addition, CT junction injuries occurred frequently in Type II as well as Type I (=CT injury). One possible cause is that the CT is subject to concentrated traction stress from both the medial and lateral hamstrings. With ultrasound, the detection rate of muscle damage around the BFLH-ST complex and SM originating tendon was high, suggesting that it is useful as an initial diagnosis. From this, it can be said that ultrasound is also useful for primary evaluation of “proximal hamstring injury”, which is prone to severe and should be given a final diagnosis using MRI. Conclusions: We created a classification system focusing on the originating tendons and clarified their incidence rates. In this study, ultrasound was found to be useful in the detection of originating tendon injuries. We also identified the characteristic sonographic findings of each type.

Background: Intra-articular injection is an important technique for treating rheumatoid arthritis and osteoarthritis of the knee. However, medication is often inaccurately injected outside of the joint. We devised an intra-articular injection method in which the needle is inserted into the suprapatellar bursa while the patient maintains isometric contraction of the quadriceps. This isometric contraction method is based on the concept that isometric contraction of the quadriceps induces contraction of the articularis genus muscle, thus expanding the lumen of the suprapatellar bursa. Methods: Intra-articular injections were performed on 150 osteoarthritic knees without effusion. The knees were alternately assigned to the isometric quadriceps method group (75 knees) and non-activated quadriceps method group (75 knees). Prior to joint injection, the anterior-posterior dimension of each suprapatellar bursa was measured to ascertain its expansion. The isometric quadriceps method was performed with the quadriceps and the articularis genus muscle maintained in a contracted state. The non-activated quadriceps method was performed in a relaxed state. Ultrasound guidance was not used for either method. Subsequently, an ultrasonic probe was used only to confirm whether the intra-articular injections were successful. We compared the accuracy of injections performed between the 2 groups. Results: Suprapatellar expansion was significantly larger (p < 0.001) using the isometric quadriceps method (2.1 ± 1.4 mm [range, 0 to 5 mm]) than using the non-activated quadriceps method (0.8 ± 0.7 mm [range, 0 to 2 mm]). The percentage of accurate intra-articular injections was significantly higher (p = 0.0287) using the isometric quadriceps method (93%) compared with the non-activated quadriceps method (80%). Conclusions: In comparison with the non-activated quadriceps method, the isometric quadriceps method led to a larger expansion of the suprapatellar bursa, which should lead to more accurate intra-articular injections. The isometric quadriceps method is effective in reducing inaccurate injections into the synovium or surrounding fatty tissues. Clinical Relevance: Putting force on the quadriceps muscle increases the success rate of intra-articular injection of the knee. The results of this study could provide a clinically relevant injection technique for future treatment.

The intra-articular injection is the most important technique for treating not only rheumatoid arthritis but also osteoarthritis of the knee. However, 1 problem is that the drug is often inaccurately injected outside of the joint, especially when no effusion is present. According to a previous systematic review by Maricar et al., the use of a superolateral patellar approach without ultrasonography had a higher success rate (87%) than both a medial midpatellar approach (64%) and an anterolateral joint-line approach (70%). For knees with little effusion, we devised a method of intra-articular injection in which the needle is inserted into the suprapatellar pouch while the patient maintains isometric contraction of the quadriceps. This method, which we call the isometric quadriceps contraction (IQC) method, is based on the concept that isometric contraction of the quadriceps induces contraction of the articularis genus muscle complex, thus expanding the volume of the suprapatellar pouch. The major steps of the procedure are (1) patient positioning and knee placement, (2) finding the puncture point, (3) isometric quadriceps contraction, and (4) needle approach to the suprapatellar pouch and injection. We also show the ultrasound evaluation of the suprapatellar pouch expansion under IQC and the accuracy of the IQC method compared with that of the non-activated quadriceps method. The results of this injection method indicate that the suprapatellar pouch is likely to expand during IQC, improving the probability of successful intra-articular injections. We believe that the IQC method is therapeutically effective and achieved a success rate of 93.3% despite the presence of little effusion and no use of ultrasonography.

Impaired subchondral bone perfusion contributes to bone marrow lesions (BMLs) in knee osteoarthritis (KOA); however, it has been assessed only under static and non-weight-bearing conditions. Dynamic, weight-bearing conditions such as walking may further compromise perfusion; therefore, understanding the resulting hemodynamics is crucial to the pathophysiology of BMLs; however, they remain unknown. This study characterized the hemodynamics of the medial aspect of the tibial tuberosity during walking in patients with KOA and BMLs using near-infrared spectroscopy (NIRS). In this cross-sectional study (March-July 2025), we compared the tibial hemodynamics during walking across four groups: young adults (n=18), older adults (n=18), KOA without BMLs (n=18), and KOA with BMLs (n=20). We used NIRS to measure changes in tissue oxygenation index (TOI) during a 3-min walking phase and a 5-min post-walking phase. BML volume was quantified using magnetic resonance imaging in the KOA-BML group only. Analysis of data from 74 participants revealed a significant group-by-phase interaction for all hemodynamic parameters using linear mixed models. Compared to the three control groups, the KOA-BML group showed a greater decrease in TOI (vs. young: MD -14.43, 95% CI [-17.30, -11.56]; vs. older adults: MD -11.94, 95% CI [-14.67, -9.21]; vs. KOA: MD -9.99, 95% CI [-12.73, -7.25]). Moreover, a lower TOI during walking correlated with a larger BML volume (r = -0.634, 95% CI [-0.840, -0.266]). Pathological hypoxia of the medial aspect of the tibial tuberosity during walking appears specific to patients with KOA-BMLs. This dynamic impairment correlates with BML volume.

Background: Proximal hamstring injuries involving the biceps femoris–semitendinosus (BF–ST) conjoint tendon are clinically challenging, yet the prognostic impact of full-layer conjoint tendon (CT) injuries remains unclear. This study aimed to determine whether CT involvement prolongs the time to return to play (RTP) compared with isolated BFLH or ST injuries. Methods: A prospective cohort of 41 university rugby players with acute proximal BF–ST complex injuries was evaluated using standardized physical examination, ultrasonography, and MRI. Injuries were classified by Type (I: full-layer CT; II: BFLH-only; III: ST-only), Zone (A–E), and Grade (0–3). RTP was defined as full participation in team training or competition. RTP differences among Types and, within Type I, across Zones and Grades were analyzed using appropriate parametric or non-parametric tests. Results: Type I injuries required significantly longer RTP (11.4 ± 4.8 weeks) than Type II (5.3 ± 2.4 weeks) or Type III (4.0 ± 1.7 weeks). In Zone C, bilateral involvement of both BFLH and ST resulted in longer RTP than unilateral BFLH injury. Within Type I, Zone A (origin detachment) showed the longest RTP (20 weeks), exceeding Zones B and C. Higher Grades were also associated with prolonged recovery. Conclusions: Full-layer CT injuries represent a distinct clinical entity with markedly delayed RTP compared with isolated BFLH or ST injuries. Classification that distinguishes CT involvement provides useful prognostic information and may enhance RTP planning in athletes.

Background/Objectives: Proximal hamstring injuries involving the biceps femoris–semitendinosus (BF–ST) conjoint tendon (CT) often exhibit delayed healing, yet the prognostic significance of CT involvement and intratendinous injury morphology has not been fully clarified. This study aimed to determine whether full-layer CT injury, particularly bilateral involvement in Zone C, prolongs return-to-play (RTP) in competitive rugby athletes. Methods: This prospective study evaluated 41 university rugby players with acute BF–ST complex injuries using clinical examination, ultrasonography, and MRI. Injuries were classified by Type (I: full-layer CT; II: BFLH-only; III: ST-only), Zone (A–E), and Grade (0–3). RTP was defined as unrestricted return to team training or match play. Group differences were analyzed using ANOVA or non-parametric tests with appropriate post hoc corrections. Results: Type I injuries required significantly longer RTP (11.4 ± 4.8 weeks) than Type II (5.3 ± 2.4 weeks) and Type III (4.0 ± 1.7 weeks), confirming the strong impact of CT involvement on prognosis. In Zone C, bilateral full-layer CT involvement was associated with an approximately twofold longer RTP duration compared with unilateral BFLH-side injuries, indicating that intratendinous tissue disruption influences recovery. These findings highlight the importance of early MRI-based assessment to identify clinically relevant tendon involvement patterns. Conclusions: Full-layer CT injuries, particularly bilateral intratendinous patterns in Zone C, markedly prolong RTP compared with isolated BFLH or ST injuries. An MRI-based classification incorporating injury type, zone, and extent of CT involvement provides clinically valuable prognostic information and may enhance RTP decision-making.