Background: Evidence, mainly from animal models, suggests that exercise during periods of pubertal growth can produce a hypertrophied anterior cruciate ligament (ACL) and improve its mechanical properties. In humans, the only evidence of ACL hypertrophy comes from a small cross-sectional study of elite weight lifters and control participants; that study had methodological weaknesses and, thus, more evidence is needed. Purpose: To investigate bilateral differences in the ACL cross-sectional area (CSA) for evidence of unilateral hypertrophy in athletes who have habitually loaded 1 leg more than the other. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We recruited 52 figure skaters and springboard divers (46 female and 6 male; mean age, 20.2 ± 2.7 years) because the former always land/jump on the same leg while the latter always drive the same leg into the board during their hurdle approach. Sport training for all participants began before puberty and continued throughout as well as after. Using oblique axial– and oblique sagittal–plane magnetic resonance imaging, we measured the ACL CSA and the anteroposterior diameter of the patellar tendon, respectively. In addition, isometric and isokinetic knee extensor and flexor peak torques were acquired using a dynamometer. Bilateral differences in the ACL CSA, patellar tendon diameter, and knee muscle strength were evaluated via 2-sided paired-samples t tests. Correlations between the bilateral difference in the ACL CSA and age of training onset as well as between the bilateral difference in the ACL CSA and years of training were also examined. Results: A significantly larger ACL CSA (mean difference, 4.9% ± 14.0%; P = .041), as well as patellar tendon diameter (mean difference, 4.7% ± 9.4%; P = .002), was found in the landing/drive leg than in the contralateral leg. The bilateral difference in the ACL CSA, however, was not associated with the age of training onset or years of training. Last, the isometric knee flexor peak torque was significantly greater in the landing/drive leg than the contralateral leg (mean difference, 14.5% ± 33.8%; P = .019). Conclusion: Athletes who habitually loaded 1 leg more than the other before, during, and after puberty exhibited significant unilateral ACL hypertrophy. This study suggests that the ACL may be able to be “trained” in athletes. If done correctly, it could help lower the risk for ACL injuries.

Background Pisiform excision and pisotriquetral arthrodesis are two surgical options for the treatment of pisotriquetral joint pain when conservative methods fail. However, it is unclear which option is best for patients who experience substantial, repetitive loading on their wrists and wish to preserve wrist flexibility and function. Case Description We present a case of bilateral ulnar-sided wrist pain related to the pisotriquetral joint in a 19-year-old collegiate diver. The pain was exacerbated by activities specific to this sport that requires wrist hyperextension, namely full weight-bearing on the hands (handstands), and has an impact on the hands and wrists upon water entry during dives due to direct palmar pressure. There were no radiographic signs of arthritis; however, there were bone marrow changes on magnetic resonance imaging (MRI). Management with rest, splinting, and corticosteroid injection failed to relieve the pain and precluded his ability to return to full-time diving. Treatment consisted of bilateral pisiform excision. Postoperatively, the patient returned to full-time competitive diving with resolution of his painful symptoms. Literature Review Pisiform excision has been shown to have successful outcomes in terms of return to play for lower impact athletes (such as badminton) but has not been reported in athletes who experience a high degree of force repetitively (such as gymnasts or divers). There is one report of pisotriquetral arthrodesis in a young gymnast with suboptimal results. Clinical Relevance This case report demonstrates that pisiform excision is a successful treatment for elite athletes who experience repetitive, palmar force on hyperextended wrists and subsequently develop ulnar-sided wrist pain.

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Objectives: Several morphological risk factors for anterior cruciate ligament (ACL) injury have been identified,1,6,12,13 including the size of the ACL.5,8,12,15 A smaller ACL volume and diameter are associated with a greater risk of injury when comparing ACL-injured subjects to matched controls.5,8,12,15 Although morphological risk factors as a group have been largely characterized as non-modifiable,9,10 ACL surface and cross-sectional areas (CSA) have the potential for modifiability, especially during growth and development.7,11 These ACL area measures have increased and the mechanical properties of the ACL have improved following exercise through periods of growth in animal models.2,7,11,14 In humans, we are only aware of one study of ACL hypertrophy—a small study of elite weightlifters.7The main purpose of this study, therefore, was to determine whether the ACL can hypertrophy in response to mechanical loading by comparing bilateral differences in ACL CSA in athletes who habitually load one leg more than the other in training for their sport. Based on the work of Grzelak et al. in weightlifters,7 as well as animal evidence that the ACL responds to exercise,2,11,14 we hypothesized that these athletes would present with significantly greater ACL CSAs in the landing/drive leg, the knee that is loaded the most in comparison with the contralateral control knee. Demonstrating the potential for the ACL to hypertrophy via mechanical loading would provide a scientific basis for exploring ACL injury prevention strategies aimed at increasing ACL CSA and robustness given that a small ACL volume and diameter are known risk factors for injury. This is particularly important for all children and especially females since they are at a much higher risk for ACL injury, and thereafter the development of knee osteoarthritis. Methods: We recruited 50 figure skaters and springboard divers because they consistently and repeatedly use one leg more than the other, thereby ensuring that one knee was habitually loaded more than the other (Table 1). More specifically, figure skaters always land their jumps on the same leg, while springboard divers always drive the same leg (‘drive’ leg) into the board during their hurdle approach. Sport training for all participants began prior to puberty and continued through and after. Bilateral knee magnetic resonance images (MRIs) were acquired with a Philips Ingenia 3.0-T scanner using a dedicated knee coil. Each knee, resting in slight flexion in the coil, was scanned using three sequences, all in the plane of the ACL: (1) oblique-sagittal (repetition time (TR): 5100 ms; echo time (TE): 30 ms; slice thickness: 2.5 mm; pixel spacing: 0.19 x 0.19 mm); (2) oblique-coronal (TR: 4000 ms; TE: 30 ms; slice thickness: 2.5 mm; pixel spacing: 0.20 x 0.20 mm); (3) oblique-axial (TR: 5100 ms; TE: 30 ms; slice thickness: 2.5 mm; pixel spacing: 0.20 x 0.20 mm). Using the oblique-axial-plane scans, the ACL CSA was measured on the three slices that were closest to 50% of the ligament’s length, and then averaged (Figure 1). Using the oblique-sagittal-plane scans, which were reconstructed to run parallel to the patellar tendon, the anteroposterior diameter of the patellar tendon was measured perpendicular to the tendon’s longitudinal axis at a distance of 2 cm distal to the patella3,4 on the slice displaying the thickest part of the tendon at that height (Figure 2). In addition, isometric and isokinetic knee extensor and knee flexor peak torques were acquired using a dynamometer. Bilateral differences in ACL CSA, PT diameter, and knee muscle strength were evaluated via one-sample t-tests that compared the mean percent difference between limbs to a null hypothesis of a zero mean percent difference. Correlations between bilateral ACL CSA differences, age of training onset and years of training were also examined. Results: Athletes with repeated unilateral lower limb loading had significantly greater ACL CSAs in the dominant knee than the non-dominant knee (Table 1; ACL CSAs: dominant = 42.0 ± 8.8 mm2; non-dominant = 40.8 ± 9.1 mm2; % difference = 4.4 ± 13.8%; t = 2.236; p = 0.030). Also, these athletes had significantly greater AP patellar tendon diameters in the dominant knee than the non-dominant knee (Table 1; patellar tendon diameters: dominant = 4.1 ± 0.6 mm; non-dominant = 3.9 ± 0.5 mm; % difference = 4.5 ± 9.4%, t = 3.322; p = 0.002). The percent bilateral difference in ACL CSA, however, was not associated with training onset (r = 0.087, p = 0.553) or years of training (r = -0.068, p = 0.641). Lastly, isometric knee flexor peak torques were significantly greater in the landing/drive leg than the contralateral knee (Table 2). Peak torques from other contraction types or muscle group did not differ between limbs (Table 2). Conclusions: Athletes who habitually loaded one leg more than the other prior to, during and after puberty exhibited significant unilateral ACL hypertrophy in their landing/drive leg. These results support existing evidence that exercise, including resistance and endurance regimens, during periods of pubertal growth has the potential to increase ACL CSA and, therefore, its strength.2,7,14 This suggests that perhaps the ACL could be ‘trained’ to become larger, more robust, and thus at lower risk of injury given that a smaller ligament is associated with a greater risk of injury. The bilateral difference in patellar tendon morphology supports our assumption that the athletes participating in this study consistently loaded one knee more than the other during their sport training, and that increased loading led to the hypertrophy of two important structures in that knee. Many gaps in knowledge—ACL development during growth and how exercise may alter its morphology and mechanical properties—need to be addressed as injury prevention strategies that involve ‘training’ the ACL are explored.