Introduction

An anterior cruciate ligament (ACL) tear is one of the most common serious knee injuries in sport. For decades the choice has been between reconstruction surgery and rehabilitation without surgery. Platelet-rich plasma (PRP) injections are now offered as a third path, or as an add-on to either.

PRP is promising, but much of what is written about it online goes beyond the evidence. At Sports Orthopedics Institute we want patients to make decisions on facts. This guide explains what PRP is, what the studies actually found, who may benefit, and what recovery looks like.

Understanding ACL tears

What does the ACL do?

The ACL runs diagonally through the centre of the knee, connecting the thigh bone (femur) to the shin bone (tibia). It stops the shin sliding too far forward, limits twisting, and helps the brain sense where the knee is.

Grades of ACL injury

Grade	What happens	Typical stability
I (mild)	Ligament stretched, not torn	Knee stays stable
II (moderate)	Partial tear	Some looseness
III (severe)	Complete tear (rupture)	Knee often "gives way"

Partial tears make up roughly 10% to 30% of all ACL tears (Zicaro et al., 2021).

How ACL tears happen

Pivoting or cutting in football, basketball, kabaddi or badminton
Landing badly from a jump
Sudden deceleration while running
A direct blow to the knee, or hyperextension

Symptoms

A pop felt or heard at the moment of injury
Swelling within a few hours
Pain and being unable to continue playing
Loss of movement and a feeling of the knee giving way

Diagnosis

A specialist examines the knee with tests such as the Lachman and anterior drawer tests. An MRI confirms the tear and shows damage to the meniscus, cartilage or other ligaments (AAOS guideline). Whether the tear is partial or complete matters a great deal for whether PRP is worth considering.

What is PRP and how might it help?

PRP is made from your own blood. A small sample is spun in a centrifuge to concentrate the platelets into a small volume of plasma, which is then injected into the injured area.

Platelets are best known for clotting, but they also release growth factors. When activated, PRP delivers platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF-1), fibroblast growth factor and others to the injury site (Gill et al., 2025).

Growth factor	Proposed role in healing
PDGF	Stimulates cell replication and new blood vessels
TGF-β	Promotes collagen and tissue matrix production
VEGF	Stimulates blood vessel formation
FGF	Supports tissue repair and cell growth
IGF-1	Regulates cell growth and differentiation

The ACL has a poor blood supply, so the idea is that PRP gives a struggling ligament the biological signals it lacks. Laboratory and animal work supports this, but results in people have been less consistent (Zhang et al., 2025). PRP preparations also vary widely between clinics, which makes studies hard to compare.

What the research shows

The evidence splits into two questions: can PRP help an injured ACL heal without surgery, and does it improve recovery after reconstruction? The short answer to both is "possibly, in the short term, and the proof is still thin."

PRP instead of surgery (non-surgical treatment)

Study	Design and size	What it found	Limits
Hada et al., Cureus 2024	Retrospective series, 10 active patients treated within 6 weeks of injury	All regained ligament continuity on MRI and returned to their pre-injury level in a mean of 139.5 days, after an average of 2.8 PRP sessions. One patient re-ruptured.	No comparison group; only 10 patients
Hada et al., Int J Surg Case Rep 2022	Two case reports, contact athletes	Both returned to their pre-injury level at 3.5 and 4 months	Two patients only
Zicaro et al., World J Orthop 2021	Prospective comparison, 40 patients with partial tears: one PRP injection plus physiotherapy vs physiotherapy alone	No difference in any outcome. 95% returned to sport in both groups. 33% (PRP) vs 31% (physio only) later needed reconstruction.	Not randomised; single, non-guided injection

Why the uncontrolled results need caution: in the KANON trial, about half of patients treated with rehab alone who did not cross over to surgery showed ACL healing on MRI two years later (Filbay et al., 2022). So healing seen after PRP cannot be credited to PRP unless a study compares it with rehab alone.

The same trial showed that rehab with optional later surgery gave results similar to early reconstruction at five years, though 51% of the rehab group did go on to have surgery (Frobell et al., BMJ 2013).

PRP during or after ACL reconstruction

Review	Trials included	What it found
Zhu et al., Orthop J Sports Med 2022	14 RCTs	PRP at a patellar-tendon graft harvest site reduced pain over the first 6 months. PRP in the graft tunnels improved pain and IKDC scores only at 3 months. No long-term benefit.
Lv et al., Platelets 2022	17 RCTs, 970 patients	Clinically important pain reduction at 6 months only; no meaningful benefit at 1 year
Cao and Wan, Orthop Surg 2022	16 RCTs, 1,025 patients	Knee scores, laxity and range of motion not improved; authors saw no current indication for routine PRP in reconstruction
Zhang et al., Front Bioeng Biotechnol 2025	24 studies	Short-term pain relief; later gains too small to matter clinically; no change in stability or graft maturation

Bottom line

PRP is safe and may help some patients with early, partial tears, but it has not yet been shown to beat good physiotherapy alone. After surgery its benefit is mainly early pain relief. Larger randomised trials are needed before it can be called a standard treatment.

Who might consider PRP for an ACL injury?

PRP may be worth discussing if you have:

A partial (Grade II) tear with some intact fibres, confirmed on MRI
A recent injury, ideally within about 6 weeks, the window used in the most encouraging studies (Hada et al., 2024)
A strong wish to try non-surgical care first, and the commitment to a full rehab programme
Reasons to avoid or delay surgery, such as age, health conditions or timing in a sports season
Planned ACL reconstruction, where PRP may reduce early pain, especially at a patellar-tendon graft site

Who is unlikely to benefit

Complete ruptures in young, active people who want to return to pivoting sport. For them, reconstruction remains the standard when surgery is indicated (AAOS guideline, 2022).
Old (chronic) tears, where the ligament ends have retracted or scarred
Knees with major meniscal tears or several torn ligaments
People with bleeding disorders, active infection, low platelets or blood thinners that cannot be paused (Bagherifard et al., 2024)

The PRP procedure: step by step

Before treatment

A specialist confirms the diagnosis with an exam and MRI and decides whether PRP is appropriate.
You will usually be asked to stop anti-inflammatory painkillers (NSAIDs) for several days beforehand, as they may blunt platelet activity. Follow your doctor's exact instructions.
Drink plenty of water and eat a light meal beforehand.

On the day (about 45 to 60 minutes, outpatient)

Blood draw: a small sample, typically 30 to 60 ml, is taken from your arm.
Processing: the blood is spun in a centrifuge to separate and concentrate the platelets.
Preparation: the PRP is drawn off and readied for injection.
Numbing: the knee is cleaned and local anaesthetic may be used.
Injection: under ultrasound guidance, PRP is placed into the injured ligament.
Dressing: a small bandage covers the site.

In the 2024 Hada study, patients received between one and five sessions, with an average of 2.8 (Hada et al., 2024). There is no agreed standard for the number of injections.

Recovery and rehabilitation

Physiotherapy does most of the work in any non-surgical ACL plan. The timeline below is a typical outline; your physiotherapist will adjust it to your progress.

Phase	Timing	Focus
Protect	0 to 48 hours	Relative rest, ice, elevation, avoid NSAIDs, weight-bearing as advised
Phase 1	Weeks 1 to 2	Gentle range of motion, isometric quads work, gait training, often a hinged brace
Phase 2	Weeks 3 to 6	Stationary cycling, closed-chain strengthening, balance work, pool therapy
Phase 3	Weeks 7 to 12	Functional strength, agility drills, return-to-running programme
Phase 4	Months 3 to 6	Sport-specific training, hop and strength testing before return to play

Progress is tracked with stability tests, strength and hop testing, patient questionnaires and sometimes a follow-up MRI. Expect soreness for a few days after each injection, and remember that ligament healing continues for many months.

PRP vs physiotherapy vs surgery

	PRP + physiotherapy	Physiotherapy alone	ACL reconstruction
Best suited to	Recent partial tears; patients avoiding surgery	Partial tears; less active patients; anyone as a first step	Complete tears with instability; pivoting sports
Return to sport (typical)	About 4 to 5 months in small studies	About 4 months in partial tears	Usually 9 to 12 months
Strength of evidence	Low: small or uncontrolled studies	Moderate: randomised trial data	Strong for restoring stability
Main downsides	Cost, multiple visits, unproven added benefit	Some patients stay unstable and need surgery later	Surgical risks, graft-site pain, long rehab

Return-to-sport figures for PRP and physiotherapy come from Hada et al., 2024 and Zicaro et al., 2021; in Zicaro's comparison the difference between the two (3.8 vs 4.3 months) was not significant.

Risks and side effects

Side effects

PRP uses your own blood, so allergic reactions are not expected. Possible effects include:

Pain and stiffness at the injection site for 1 to 3 days
Bruising or minor bleeding
A very small risk of infection
No improvement, which may lead to surgery later

Questions to ask your doctor

Is my tear partial or complete, and how stable is my knee?
What would you expect from physiotherapy alone, without PRP?
How many injections do you recommend, and how is your PRP prepared?
Will the injection be ultrasound-guided?
How will we judge whether it is working, and when?
If it does not work, what is the plan and timeline for surgery?

Frequently asked questions

Can PRP heal a completely torn ACL?

There is no good evidence that it can. A complete rupture that leaves the knee unstable is usually treated with reconstruction. PRP is studied mainly in partial tears and as an add-on to surgery.

How many PRP injections will I need?

There is no standard. In one recent study, patients had one to five sessions, averaging about three (Hada et al., 2024). Your doctor will tailor this to your injury.

Is the PRP injection painful?

Most people feel mild to moderate discomfort. Local anaesthetic helps, and soreness usually settles within one to three days.

How soon can I return to sport after PRP?

In small studies, active patients with recent injuries returned to their previous level in about 4 to 5 months. Return depends on passing strength and hop tests, not just on time.

What is the success rate of PRP for ACL tears?

No reliable success rate exists yet. In the only comparative study of partial tears, about one in three patients needed reconstruction later, with or without PRP (Zicaro et al., 2021).

Can PRP be used after ACL reconstruction?

Yes. Reviews show it can reduce pain in the first months after surgery, but it has not been shown to improve knee function or stability in the long term (Lv et al., 2022).

Is PRP covered by insurance in India?

Usually not. Most insurers consider it investigational. Check your policy before treatment.

Conclusion

PRP is a safe, low-risk option that may help selected patients with recent partial ACL tears, and it can ease early pain after reconstruction. It is not a substitute for surgery when the knee is unstable, and it has not yet been shown to outperform good rehabilitation alone.

At Sports Orthopedics Institute, we match treatment to your tear, your knee's stability and your goals. If you have an ACL injury, book a consultation to discuss whether PRP, physiotherapy or reconstruction is right for you.

References

Hada S, Hada M, Yoshida K, et al. Conservative treatment using platelet-rich plasma for acute anterior cruciate ligament injuries in highly active patients: a retrospective survey. Cureus. 2024;16(1):e53102. doi:10.7759/cureus.53102
Hada et al. Two cases of contact athletes with anterior cruciate ligament injuries who returned to competition early after conservative treatment with PRP therapy. Int J Surg Case Rep. 2022. PMC9168593
Zicaro JP, Garcia-Mansilla I, Zuain A, et al. Has platelet-rich plasma any role in partial tears of the anterior cruciate ligament? Prospective comparative study. World J Orthop. 2021;12(6):423-432. doi:10.5312/wjo.v12.i6.423
Zhu T, Zhou J, Hwang J, Xu X. Effects of platelet-rich plasma on clinical outcomes after anterior cruciate ligament reconstruction: a systematic review and meta-analysis. Orthop J Sports Med. 2022;10(1):23259671211061535. doi:10.1177/23259671211061535
Lv ZT, Zhang JM, Pang ZY, et al. The efficacy of platelet rich plasma on anterior cruciate ligament reconstruction: a systematic review and meta-analysis. Platelets. 2022;33(2):229-241. doi:10.1080/09537104.2021.1902969
Cao Y, Wan YD. Effectiveness of platelet-rich plasma in anterior cruciate ligament reconstruction: a systematic review of randomized controlled trials. Orthop Surg. 2022. doi:10.1111/os.13279
Zhang Y, Xiao Z, Fan Z, et al. The impact of platelet-rich plasma injection on anterior cruciate ligament reconstruction: a systematic review and meta-analysis. Front Bioeng Biotechnol. 2025;13:1625271. doi:10.3389/fbioe.2025.1625271
Gill SS, Cenci G, Falcinelli S, et al. Platelet rich plasma and anterior cruciate ligament repair: a new frontier, or a short term adjunct. World J Orthop. 2025;16(1):100693. doi:10.5312/wjo.v16.i1.100693
Frobell RB, Roos HP, Roos EM, et al. Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial. BMJ. 2013;346:f232. PubMed
Filbay S, Roemer F, Lohmander L, et al. Evidence of ACL healing on MRI following ACL rupture treated with rehabilitation alone may be associated with better patient-reported outcomes: a secondary analysis from the KANON trial. Br J Sports Med. 2022. Summary
Brophy RH, Lowry KJ. American Academy of Orthopaedic Surgeons clinical practice guideline summary: management of anterior cruciate ligament injuries. J Am Acad Orthop Surg. 2023;31(11):531-537. PMC10168113
Bagherifard A, Sahrai R, Mokhtari K, Yahyazedeh H. Therapeutic impact of platelet-rich plasma on anterior cruciate ligament injury: a mini-review. J Res Orthop Sci. 2024;11(1):1-14. PDF

This article is for general information and is not a substitute for professional medical advice. Please consult a qualified orthopedic surgeon about your own condition.

PRP Therapy for ACL Tears: What the Evidence Really Shows