Study (y)

Study Design

Intervention

Inclusion

Outcomes

Rodas, et al. (2021) [69]

II

1) 2 injections of LP-PRP 23 days apart and standardized rehabilitation protocol (n = 10)

2) BM-MSC injection and standardized rehabilitation protocol (n = 10)

Athletes with chronic patellar tendinopathy with pain for > 4 months (mean, 23.6 months) and unresponsive to nonoperative treatments. Intratendinous lesion > 3mm at the proximal insertion.

·         Significant reduction in VAS pain scores in daily life and sports activities at 6 months, but no statistically significant difference between the two groups at 6 months.

·         Statistically significant improvement in VISA-P scores in both groups at 6 months. Scores were > 60 (suitable for intense athletic activity) in both groups with no significant difference in scores between groups.

·         Statistically significant improvements in tendon structure on 2-D ultrasound, UTC, and MRI for BM-MSC group only.

Lee, et al. (2020)

Case series

1) PRP injection and a 2-week period of rest from physical lower body activity, no anti-inflammatory medication, and no treatment with cooling or ice (n = 15)

Elite athletes with refractory chronic patellar tendinopathy

·         12 athletes were eventually able to fully return to sport after the PRP injection (range 3 weeks to 16 weeks).

·         3 of the athletes required surgical debridement and repair of the patellar tendon.

Kaux, et al. (2019) [72]

II

1) Single LP-PRP injection and standardized eccentric training protocol (n = 18)

2) 2 HA injections 1 week apart and standardized eccentric training protocol (n = 15)

Sportsmen with chronic patellar tendinopathy unresponsive to classical conservative treatments (painkillers, NSAIDs, eccentric training, ESWT)

·         Significant improvement in VAS, VISA-P, and IKDC for both groups at 6- and 12-week follow-ups. No statistically significant differences in these scores between the two intervention groups.

Scott, et al. (2019) [70]

I

1) 15% hematocrit in 3.5 mL PRP and standardized rehabilitation program (n = 19)

2) 2% hematocrit in 3.5 mL PRP and standardized rehabilitation program (n = 19)

3) 3.5 mL saline and standardized rehabilitation program (n = 19)

Recreational/elite athletes with patellar tendinopathy symptoms for at least 6 months that were not resolved with exercise-based rehabilitation for a minimum of 6 weeks

·         No significant difference in mean change of VISA-P scores, NPRS scores, nor GROC scores at 6-, 12-, 24-, and 52-weeks following treatment. A nonsignificant trend for poorer outcomes was noted in the LR-PRP group.

Manfreda, et al. (2019) [79]

Prospective study

1) 3 PRP injections in 15 days, for all patients followed by rehabilitation (n = 23)

Athletes who did not want to undergo surgery and who are non-responders to other conservative treatments for the chronic patellar tendinopathy

·         Both for VAS and for VISA-P, there was no significant difference in results at 4 and 12 months compared to baseline (p > 0.05).

Zayni, et al. (2015) [5]

Randomized prospective consecutive series

1) Single PRP injection and physical therapy (n = 20)

2) Two PRP injections (2 weeks apart) and physical therapy (n = 20)

Elite/competitive non-elite athletes with chronic anterior knee pain with focal tenderness at the proximal insertion of patellar tendon on clinical examination

·         23% of PRP patients had failed PRP treatment and needed surgery.

·         Patients that received 2 PRP injections had significantly better clinical scores than those who received a single PRP injection with VAS, Tegner score, and VISA-P.

Dragoo, et al. (2014) [71]

Double-blind, randomized controlled trial

1) Dry-needling and standardized eccentric exercises (n = 13)

2) Single injection of ultrasound-guided LR-PRP, dry-needling, and standardized eccentric exercises (n = 10)

Patellar tendinopathy which had failed nonoperative treatment

·         At 12 weeks the PRP group showed a statistically significant improvement in VISA scores compared to the dry-needling group (p = 0.02).

·         At 12 weeks the difference in improvement in Lysholm scores was not significant (p > 0.05).

·         At > 26 weeks, the dry-needling group showed significant improvement in Lysholm scores compared to the PRP group (P = 0.006).

·         At > 26 weeks, the difference between VISA score improvement was not significant (p > 0.05).

Charousset, et al. (2014) [73]

Prospective Study

1) Athletes with chronic patellar tendinopathy refractory to nonoperative management and received PRP injections (3 consecutive injections 1 week apart: n = 28)

Professional/semi-professional athletes with chronic anterior knee pain, tenderness at the inferior pole of the patella, or pain during provocative tests of the knee extensors and morphological signs of chronic patellar tendinopathy

·         The VISA-P, VAS, and Lysholm scores all significantly improved at the 2-year follow-up.

·         21 of the 28 athletes returned to their pre-symptom sporting level at 3 months.

·         MRI assessment showed improved structural integrity of the tendon at 3 months after the procedure and complete return to normal structural integrity of the tendon in 16 patients.

·         7 patients did not recover their pre-symptom sporting level, 3 patients returned to sport at a lesser level, 1 patient changed his sport activity, and 3 needed surgical intervention.

Filardo, et al. (2013) [74]

Prospective study

1) 3 intratendinous injections of PRP (2 weeks apart). After the second injection the patients were instructed to start a rehabilitation program based on eccentric exercises to be carried out for about 12 weeks (n = 43)

Chronic patellar proximal tendinopathy that has undergone unsuccessful conservative or surgical management

·         Significantly poorer results were obtained in patients with a longer history of symptoms, and poor results were also observed in bilateral lesions.

·         VISA-P score significantly increased from baseline to two months, to six months, and to four years.

·         EQ-VAS score significantly increased from baseline to two months and to six months.

Vetrano, et al. (2013) [62]

Randomized controlled trial

1) 3 sessions of ESWT at 48- to 72-hour intervals and standardized stretching and muscle strengthening protocol for 2 weeks (n = 23)

2) 2 ultrasound guided PRP injections over 2 weeks (1 per week) and standardized stretching and muscle strengthening protocol for 2 weeks (n = 23)

Athletes who had chronic patellar tendinopathy for at least 6 months before treatment and failure of nonoperative treatment

·         Both treatments led to improvement from baseline VISA-P and VAS scores at 2, 6, and 12 month follow-ups (P < 0.005 for all).

·         At 6 and 12 months, the PRP group significantly improved in VISA-P and VAS scores when compared to the ESWT group.

Gosens, et al. (2012) [75]

Prospective Study

1) Patients that had been treated with cortisone, ethoxysclerol and/or surgical treatment before PRP injection (n = 14)

2) Patients had not received an injection or surgical treatment before their PRP injection (n = 22)

**All patients had visited a physiotherapist and eccentric exercises had been performed exhaustively before being treated with PRP.

Chronic patellar tendinopathy

· VISA-P significantly improved in group 2 from baseline to follow-up (average 18 months).

· Group 1 did not show significant improvement on VISA-P.

· VAS ADL scores, VAS sport scores, and VAS work scores significantly improved in both groups.

Fildaro, et al. (2010)

Prospective study

1) Patients affected by chronic jumper’s knee, who had failed previous nonsurgical or surgical treatments, with multiple PRP injections (3 occasions over 2 weeks) and physiotherapy (n = 15)

2) Patients who had not undergone any treatment (for at least two months) and were primarily treated with the physiotherapy protocol alone (n = 16)

Athletes with >3 months of exercise-associated pain and failed to respond to other nonsurgical treatments

· PRP group experienced a significant improvement in the EQ VAS and pain level was identified from baseline evaluation to the end of the injection cycle, and at six-month follow-up.

· When comparing the two groups, no statistically significant differences were obtained with the EQ VAS and pain level evaluation, as with time-to-recover and patient satisfaction (p > 0.05).

· When compared to the control group, the PRP group had a statistically significant improvement in sport activity level.

Kon, et al. (2009) [61]

Prospective Study

1) 3 PRP injections (injections were administered every 15 days). Rest between 1^st and 2^nd injection, mild activities after 2^nd injection, stretching exercises and mild activities after 3^rd injection (n = 20)

Athletes with > 3 months of exercise-associated pain and failed to respond to other nonsurgical treatments

· At 6 months, the patients reported significantly improved Tegner, EQ VAS, and SF 36 Q scores.

Abbreviations: EQ VAS: EuroQol-Visual Analogue Scales; ESWT: Extracorporeal Shock Wave Therapy; GROC scores: Global Rating of Change Scale; HA: Hyaluronic Acid; IKDC: International Knee Documentation Committee Form Score; Lysholm Score: Lysholm Knee Scoring Scale; NPRS scores: Numerical Pain Rating Scale; BM-MSC; Single Bone Marrow-Derived Mesenchymal Stem Cell; SF 36 Q Scores: 36-Item Short Form Health Survey; Tegner Score: Tegner Activity Score; UTC: Ultrasound Tissue Characteristics; VAS: Visual Analog Scale; VAS-ADL: Visual Analog Scale-Activities of Daily Living; VISA-P: Victorian Institute of Sport Assessment-Patellar Tendinopathy