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Treatment of patellar and hamstring tendinopathy with platelet-rich plasma in varsity collegiate athletes: A case series
∗Corresponding author: Kenneth Y. Lee. k.lee@northwestern.edu
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
Patellar and hamstring tendinopathy are common injuries among elite athletes. Platelet-rich plasma (PRP) has emerged as a promising new therapy for accelerating healing and shortening recovery in patients with these conditions. We present 15 cases of PRP injection used for either patellar or hamstring tendinopathy in varsity collegiate athletes at a single institution. All of the athletes in our case series with hamstring or patellar tendinopathy were fully able to return to sport. Three of the athletes with patellar tendinopathy were referred for surgery, while none of the athletes with hamstring strain underwent a subsequent surgical procedure.
Keywords
Tendinopathy
Patellar
Hamstring
Platelet-rich plasma
Collegiate
Arthrex
1 Introduction
Platelet-rich plasma (PRP) is a promising therapy that introduces platelets and cytokines to a region of degenerative tissue to help accelerate healing and shorten recovery time.1 For decades, PRP injections have been used in various clinical settings, but inconclusive evidence supporting its use has resulted in only recent application in sports medicine. Literature on the efficacy of PRP injections in collegiate athletes is even less available.2
PRP injections have been reportedly used to treat a variety of injuries.1 Current evidence shows mixed results for the efficacy of PRP injections in treating hamstring strains.3–5 Hamid et al. concluded in a study of 28 individuals that acute hamstring injuries managed with PRP injections and rehab resulted in significantly faster recovery than a rehab protocol on its own.6 In addition, evidence surrounding the use of PRP injections in treating patellar tendinitis7–9 and other tendinopathies2 have been without consensus thus far. Zayni et al. investigated the benefits of multiple PRP injections in the treatment of athletes with chronic patellar tendinitis; they observed significant improvements in athlete performance after multiple injections were administered as opposed to a single injection,10 but was unable to establish the ideal number of injections and superior formulation. These studies suggest that PRP may be an effective treatment for chronic sports-related injuries. This study seeks to investigate the efficacy of PRP injections in treating varsity collegiate athletes at one institution with patellar or hamstring tendinopathy.
2 Case presentations
The following cases describe athletes treated at a single Division I collegiate institute by a single sports medicine team over a 5-year period between 2013 and 2018, inclusive. All reported cases of hamstring injury and patellar tendinopathy were reviewed. Injections of platelet-rich plasma were done at the point of maximal tenderness in conjunction with MRI findings and without the use of ultrasound guidance. The Arthrex Angel system was used to prepare all PRP injections uniformly from 60 cc of whole blood. Standard protocol following each PRP injection included a 2-week period of rest from physical lower body activity, no anti-inflammatory medication, and no treatment with cooling or ice. Return to sport was defined as medical clearance of an athlete for full participation in their respective varsity sport, including practice, game, or other team-related activities.
The team involved in this study does not provide supplements for its varsity athletes. The athletes included in this study have never tested positive for performance enhancing drugs. The institution's ethics review board approved this study.
2.1 Disclosure of interest
The authors have no conflicts of interest to report.
2.2 Patellar tendinopathy
2.2.1 Case 1
A 20-year-old male varsity college basketball player presented with left anterior knee pain that had been worsening over 3 months. Physical examination demonstrated tenderness to palpation over the inferior pole of the patella. MRI showed increased signal enhancement in the middle third of the posterior half of the patellar tendon, indicating a partial patellar tendon tear. The patient was managed conservatively with activity modification, patellar tendon PRP injection, and a knee immobilizer. At nine weeks follow-up the patient reported improvement in his anterior knee pain and no longer had point tenderness over the inferior patella. He was cleared to return to full sport participation. After returning to sport, his symptoms returned and continued to worsen. At 13 weeks post-PRP injection, he underwent left knee patellar tendon debridement and partial repair. At twelve weeks post-surgery he successfully returned to running activities and returned to full sport 6 months post surgery.
2.2.2 Case 2
A 19-year-old female basketball player with a history of worsening left anterior knee pain for 16 weeks. Physical examination demonstrated full active ROM with tenderness to palpation along the inferior pole of the patella. MRI showed increased signal enhancement in the proximal middle third of the patellar tendon, indicating a partial patellar tendon tear. The patient was subsequently removed from sport-related activity, placed in a knee immobilizer, and underwent a patellar tendon PRP injection. The patient continued to treat her patellar tendonitis with physical therapy, NSAIDs, activity modification, and cryotherapy. She returned to full sport, 8 weeks following the PRP injection.
2.2.3 Case 3
A 19-year-old female volleyball player with no significant past medical history presented complaining of 2 weeks of worsening bilateral anterior knee pain. Physical examination demonstrated full active ROM with tenderness to palpation along the inferior pole of the bilateral patellar tendons. MRI showed an OCD lesion on the dorsal aspect of her left patella. The decision was made to treat her bilateral patellar tendinitis conservatively, and the patient was managed with activity modification, cryotherapy, and bilateral patellar tendon PRP injections. The patient continued to treat her knee pain with physical therapy, NSAIDs, activity modification, and cryotherapy. She returned to full sport 12 weeks following the PRP injections.
2.2.4 Case 4
A 19-year-old female basketball player with a history of bilateral patellar tendonitis in high school presented complaining of worsening left > right bilateral anterior knee pain for 1 week. Physical examination demonstrated full active ROM with tenderness to palpation bilaterally of the distal third of the patellar tendon near the insertion of the patellar tendon on the tibia. MRI of both knees showed enhanced signal of the bilateral patellar tendons at the distal insertion. At 20 weeks after presentation the decision was made to proceed with bilateral patellar tendon PRP injections. The patient continued to treat her patella tendonitis with physical therapy, NSAIDs, activity modification, and cryotherapy. She returned to full sport 11 weeks following PRP injections.
2.2.5 Case 5
A 21-year-old male basketball player with a history of chronic, intermittent right patellar tendonitis presented with 1 week of worsening right anterior knee pain. Physical examination demonstrated full active ROM with tenderness to palpation over the proximal origin of patellar tendon. MRI showed signal enhancement of the central third, posterior surface of the proximal patellar tendon, indicating a partial patellar tendon tear. Four weeks after presentation, the decision was made to proceed with patellar tendon PRP injection. He progressed back to full sport activity 4 weeks following the injection.
2.2.6 Case 6
A 20-year-old male football player with a history of left patella tendonitis presented complaining of acute on chronic left anterior knee pain for 1 day. Physical examination demonstrated full active ROM with tenderness to palpation over the inferior pole of the patella. MRI showed signal enhancement of the middle third of the patellar tendon. The patient was managed conservatively with activity modification and physical therapy for 12 weeks. His activity related knee pain symptoms continued to worsen. Twelve weeks after presentation, the decision was made to proceed with a patellar tendon PRP injection. His symptoms returned after returning to sport-related activity. He continued to manage his pain with bracing, physical therapy, and cryotherapy. At 12 weeks post-injection, his symptoms had not significantly improved, and the decision was made to proceed with patellar tendon debridement and partial repair. At 4-weeks post-op the patient symptoms had resolved, and he was cleared to progressively return to sport. He returned to full sport without restrictions 6 weeks post-op.
2.2.7 Case 7
A 19-year-old male football player with no significant past medical history presented with worsening right anterior knee pain for 4 weeks. Physical examination demonstrated full active range of motion, tenderness to palpation of the patella tendon. The athlete was initially treated with activity modification, cryotherapy, and NSAIDs. His symptoms continued to progress over the next 4 weeks and began to significantly limit his activity level. MRI showed signal enhancement of the proximal middle third of the patellar tendon, indicating a high-grade partial patellar tendon tear. The decision was made to proceed with surgical debridement of the right patellar tendon as well as a patellar tendon PRP injection. At 16 weeks post-op the patient was cleared to progress back to running activities. The athlete successfully returned to full sport at 20 weeks post-op.
2.3 Hamstring musculotendinopathy
2.3.1 Case 8
An 18-year-old male football player presented with a 1-day history of left hamstring pain following a “pop” sensation in the middle of a game. Physical examination showed no ecchymosis nor palpable defect and tenderness to palpation at the medial hamstring musculotendinous junction. Ultrasound showed a small gap in the left medial hamstring. The decision was made to proceed with a left hamstring PRP injection 3 days following symptom onset. The athlete's symptoms progressively improved and he successfully returned to full sport at 3 weeks post-injection.
2.3.2 Case 9
A 19-year-old male football player with a history of recurrent right hamstring strains presented with a 1-day history of right hamstring pain following a “pop” sensation while running in practice. Physical examination demonstrated tenderness to palpation over the proximal hamstring origin at the ischial tuberosity. MRI confirmed a grade 1–2 strain of the proximal biceps femoris and semitendinosus musculotendinous junction. The athlete underwent a hamstring PRP injection 9 weeks following symptom onset. At 5 weeks post-injection the athlete's symptoms had resolved, and he was fully cleared to return to sport.
2.3.3 Case 10
A 20-year-old male football player presented with right hamstring pain after a “pop” sensation in his posterior thigh during practice 2 days prior to presentation. Physical examination showed a mild tenderness to palpation of the right hamstring muscle belly and extending distally to the myotendinous junction. He was treated with a hamstring PRP injection 10 days following symptom onset. Nine weeks after the injection and targeted rehab, the athlete was fully cleared for return to sport.
2.3.4 Case 11
A 19-year-old male football player presented with a 1-day history of left proximal hamstring pain following a “pop” that caused him to miss the remainder of practice. Physical examination demonstrated tenderness to palpation along the proximal hamstring near its attachment to the ischium. MRI confirmed edema in the biceps femoris. The athlete underwent a PRP injection 3 days following symptom onset. At 16 weeks post-injection, the athlete was able to return to full activity.
2.3.5 Case 12
A 22-year-old male football player presented with chronic left hamstring pain, which began when running a route at practice 1 month prior to presentation. During this time, he had tried various combinations of rest, anti-inflammatory medications, and icing treatments. Physical examination demonstrated tenderness at the distal hamstring muscle belly. MRI confirmed complete disruption of the left hamstring distal myotendinous junction. The athlete was given a PRP injection 1 month after symptom onset and was cleared to return to sport 10 days following injection.
2.3.6 Case 13
A 21-year-old female soccer player presented with a 2-month history of chronic left hamstring pain. The athlete could not identify an acute inciting event for her pain. Physical examination revealed tenderness to palpation over the distal biceps femoris and the popliteus tendon. MRI showed strain of the distal musculotendinous junction of the biceps femoris. The decision was made to proceed with PRP injection 10 weeks following symptom onset, and the athlete was cleared to progress to jogging and cutting two weeks post-injection. The athlete successfully returned to full sport 5 weeks post-injection.
2.3.7 Case 14
A 19-year-old male football player with a past medical history significant for recurring right hamstring strains presented with chronic right hamstring pain after feeling a sharp pain during practice 1 day prior to presentation. Physical examination showed mild tenderness and spasm over the proximal mid-belly of the right hamstring. MRI showed strain of the proximal mid-semimembranosus tendon. The athlete received a right hamstring PRP injection 1 week following symptom onset. The athlete was later cleared for return to sport 12 weeks post-injection.
2.3.8 Case 15
A 22-year-old male football player with past medical history significant for recurring right hamstring strains presented complaining of 3 weeks of acute right hamstring pain with no clear inciting event. Physical examination demonstrated mild tenderness to palpation in the mid-belly of the right biceps femoris. MRI displayed strain of the muscle belly of the biceps femoris. The athlete underwent subsequent PRP injection 4 weeks following symptom onset. The athlete was successfully cleared for return to sport 16 weeks post-injection.
3 Discussion
Though PRP use is common, there is a clear gap in literature surrounding the efficacy of its use for both patellar and hamstring tendinopathy in varsity collegiate athletes.
A small study treated 15 patients with refractory chronic patellar tendinopathy and found significant improvement in pain scores and sport activity level achieved following use of PRP injections.11 These study presents conflicting evidence with earlier published results, which found no significant improvement in chronic patellar tendinopathy recovery with use of PRP.8
Studies assessing the impact of patellar tendinopathy on athletes have found it to be an extremely debilitating injury. In our small case series, all but one of the varsity athletes who underwent PRP treatment for chronic patellar tendinopathy were fully cleared for return to sport within four months, and all athletes who received treatment were able to return to full sport by 10 months.
Although all of the athletes with patellar tendinopathy within this case series were eventually able to fully return to sport, it was noted that 3 of the athletes required surgical debridement and repair of the patellar tendon. This observation remains consistent with current literature on patellar tendinopathy treatment, which shows that although conservative treatments such as rest, anti-inflammatory treatment, and physiotherapy are generally considered first-line for treating patellar tendinopathy, elite athletes frequently do not respond to conservative therapy; these athletes are then indicated for surgical intervention including patellar debridement and partial repair of the patellar tendon.12 In addition, the ability for all 3 of the athletes in this case study to fully return to sport following surgery is also supported by the literature. Brockmeyer et al. found that 91% of athletes undergoing arthroscopic repair of chronic patellar tendinopathy were able to return to preinjury level of activity.13
Literature concerning return to sport among collegiate athletes with chronic patellar tendinopathy is admittedly limited to date. However, this small series suggests that there may be benefit with PRP use for chronic patellar tendinopathy in promoting return to sport among varsity collegiate athletes. In addition, further investigation is needed with a larger cohort to establish the long-term benefits of PRP use in this patient population.
Like patellar tendinopathy, management of hamstring injuries tends to vary considerably in medical literature.14 Though the widespread use of PRP to treat this injury has been demonstrated, evidence behind its efficacy has been inconclusive thus far. Hamid et al. found faster recovery in grade 2 hamstring muscle injuries using PRP injection combined with a rehabilitation program versus a rehabilitation program alone, with mean return to play found to be 26.7 and 42.5 days, respectively.6 In contrast, Hamilton et al. found no benefit to PRP injections over intensive rehabilitation in athletes sustaining acute, MRI positive hamstring injuries in 90 patients.4
Chronic, recurrent hamstring injuries may react differently than acute injuries. Studies have already demonstrated the different nature of chronic hamstring injury, including significantly longer time lost to injury.15 When suggesting lack of benefit with PRP injections, Hamilton et al. specifically listed “reinjury or chronic hamstring injury” as an exclusion criteria for the study.4 Many elite athletes, including varsity collegiate athletes, experience chronic hamstring injury given the extremely high rate of recurrence with primary hamstring injuries.14 Further investigation is required to uncover the efficacy of PRP injections in acute and chronic hamstring tendinopathy and return to sport in varsity athletes.
Overall, Tables 1 and 2 show that all of the varsity collegiate athletes in our case series with hamstring or patellar tendinopathy were fully able to return to sport. Three of the athletes with patellar tendinopathy were referred for surgery, while none of the athletes with hamstring strain underwent a subsequent surgical procedure.
| Sex | Sport | Age (years) | Duration of symptoms before injection | Post-injection return to sport (weeks) | Need for surgery | Return to sport following surgery (weeks) | |
| Patellar tendon | Male | Basketball | 20 | 13.5 | 40 | Yes | 27 |
| Female | Basketball | 19 | 16 | 8 | No | N/A | |
| Female | Basketball | 19 | 2 | 12 | No | N/A | |
| Female | Basketball | 19 | 20 | 11 | No | N/A | |
| Male | Basketball | 21 | 4 | 4 | No | N/A | |
| Male | Football | 20 | 12 | 16 | Yes | 6 | |
| Male | Basketball | 19 | 8 | 16 | Yes | 16 |
| Sex | Sport | Age | Duration of symptoms before injection (weeks) | Post-injection return to sport (weeks) | Need for surgery | Return to sport following surgery (weeks) | |
| Hamstring | Male | Football | 18 | 0.5 | 3 | No | N/A |
| Male | Football | 19 | 9 | 5 | No | N/A | |
| Male | Football | 20 | 1.5 | 9 | No | N/A | |
| Male | Football | 19 | 0.5 | 16 | No | N/A | |
| Male | Football | 22 | 4 | 3 | No | N/A | |
| Female | Soccer | 21 | 10 | 5 | No | N/A | |
| Male | Football | 19 | 1 | 12 | No | N/A | |
| Male | Football | 22 | 4 | 16 | No | N/A |
There are some notable limitations to this study. First and foremost, the authors only accessed data for one collegiate institution. This restricts the results found in this study and perhaps applicability to collegiate varsity athletes at other institutions with varying protocols and PRP formulations. In addition, the retrospective nature of this study lens itself to unavoidable confounders. Accuracy of documentation for injury severity may have been variable depending on the practitioner and/or medical staff caring for the athletes included in this study. Injury prevention level may have been variable among athletes and sports, and compliance to rehabilitation protocols may have varied significantly. Finally, assessing the benefit of PRP injections in athletes who underwent other preceding or subsequent procedures was also a limitation to this study. Further randomized controlled trials must be performed to fully assess the efficacy of PRP injections in treating hamstring injuries and patellar tendinopathies in varsity collegiate athletes.
4 Conclusion
Both patellar tendinopathies and hamstring injuries are extremely common, often recurrent injuries among elite athletes that can often result in lengthy recovery times.
There is a gap in current literature on the use of PRP injections in treating both conditions, specifically in varsity collegiate athletes. Although evidence surrounding the use of PRP injections in chronic patellar and hamstring tendinopathy has been mixed to this point, this case series supports its use in promoting return to sport in varsity athletes.
Author contributions
KL: Conceptualization, Methodology, Formal analysis, Investigation, Writing – Original Draft, Project Administration.
HB: Conceptualization, Methodology, Formal analysis, Investigation, Writing – Original Draft.
CH: Data curation, Writing – Review & Editing.
VT: Conceptualization, Resources, Writing – Review & Editing, Supervision.
MT: Writing – Review & Editing, Supervision.
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