Partial ACL tear
Also called: sprained acl, pulled acl, grade 2 acl tear, grade 1 acl sprain, partial thickness acl tear. Clinical name: Partial tear or sprain of the anterior cruciate ligament (grade 1 to 2 ACL injury).
A grade 1 ACL sprain often settles within about 3 to 6 weeks of rehab. A partial (grade 2) tear usually needs at least 3 months of progressive physiotherapy, and longer if the knee keeps feeling unstable.
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What it actually is
A partial ACL tear means part of the anterior cruciate ligament, the band deep inside the knee that stops the shin bone sliding forward and twisting, has been torn, while the rest is intact. A sprain (grade 1) is milder still: the ligament is overstretched but not torn. Both usually follow a twist, pivot or awkward landing, with pain and swelling over the next few hours.
The good news is that these grades are often managed without surgery. Because part of the ligament is still working, a structured rehab programme that strengthens the muscles around the knee and retrains balance and control can get many people back to normal activity and sport. A grade 1 sprain often settles in weeks; a partial tear usually needs at least three months of progressive physiotherapy.
The thing that decides the path is stability. If the knee keeps feeling loose or giving way during activity despite good rehab, that’s the signal to see a surgeon about whether a reconstruction would help. For the full picture across every grade, see the main ACL injury guide, and if surgery does end up on the table, the ACL surgery recovery timeline walks through it month by month.
How bad is it?
Injuries like this are usually described in grades. The grade is what shapes your timeline and what you can safely do while it settles.
The ligament is overstretched but not torn, and it's still holding the knee stable. Swelling and soreness settle with rest, swelling control and a gradual return to loading, and most people are back to normal activity within weeks.
Part of the ligament is torn and it has become looser. AAOS says partial tears may be treated without surgery using progressive physical therapy, with rehabilitation that usually lasts at least 3 months. How stable the knee feels during activity decides whether that's enough.
How long will it take?
Recovery moves in phases. This is the typical shape of it. Yours may run faster or slower, and the numbers below are general ranges, not a forecast for your specific injury.
When to get it looked at
Most cases settle with time and sensible loading. Get it assessed by a professional if any of these apply, as they can point to something that needs hands-on care:
- The knee gives way or buckles under you, or feels like it might
- Marked swelling that came on within a few hours of the injury
- You can't fully straighten or fully bend the knee
- The knee locks or catches and won't move past a certain point
- You can't put weight through the leg or walk on it
- A loud pop at the moment of injury followed by the knee feeling unstable
This is a list of warning signs, not a diagnosis. If you are worried, see your GP or a physiotherapist. In Ireland an injury unit or out-of-hours GP can see you the same day (in the UK, call NHS 111). For a severe or sudden injury, go to an emergency department or call 112 or 999.
What to track while you recover
With a partial tear, the real question is whether the knee is becoming stable enough, and that's hard to judge from one good or bad day. A short daily record makes the trend obvious, for you and for whoever is guiding the rehab.
- Any moments the knee felt unstable or gave way, and what you were doing (the number that matters most)
- Swelling around the kneecap: more, less or the same as yesterday
- How far it straightens and bends compared with the other knee
- Which rehab exercises you did and how the knee responded the next day
- Single-leg balance or hop tests as they get easier
This is exactly what InjuryLog does.
Log each of these in seconds, watch the trend build day by day, and keep every scan and receipt tied to this one injury. Free on iOS and Android.
What to tell your physio
The first appointment goes further when you can describe exactly how it happened and how the knee has behaved since, not just how it feels today.
- Exactly how it happened: the twist, pivot or landing, and whether you heard or felt a pop
- How quickly it swelled, and whether the knee has given way since
- What you can and can't do now: straighten it, bend it, put weight through it, walk, go down stairs
- Your goal: everyday activity, a physical job, or pivoting sport, because it shapes the treatment
- Any previous knee injuries on either side
Walk in with the whole picture.
InjuryLog turns your daily logs into a clean Physio Visit Pack, a one-page summary your physio can actually read, so the first appointment starts with facts, not guesswork.
The questions people actually ask
How long does a grade 2 ACL tear take to heal?
Usually at least 3 months. AAOS says partial ACL tears may be treated without surgery using progressive physical therapy, and that the recovery and rehabilitation usually lasts at least 3 months. Some take longer, particularly if the knee still feels loose during sport. The timeline is set by how stable and strong the knee becomes, not by a fixed date, so it's reviewed as you go.
How long does a sprained ACL take to heal?
A mild grade 1 sprain, where the ligament is stretched but not torn, often settles within about 3 to 6 weeks with rest, swelling control and a gradual return to activity. If it's still swollen, painful or unstable after a couple of weeks, it may be more than a sprain and is worth having assessed. Everyone heals differently, so treat these as typical ranges rather than a promise.
How is a grade 2 ACL tear treated?
Most often without surgery to begin with. AAOS describes progressive physical therapy for partial tears, and the NHS lists physiotherapy to strengthen the knee, a knee brace during exercise and pain relief as the alternatives to surgery. AAOS recommends around 12 weeks of non-surgical treatment for acute isolated ACL tears. If the knee keeps giving way despite good rehab, a surgeon may discuss reconstruction.
Is my ACL torn or sprained?
You can't reliably tell from the symptoms alone. Both can follow a twist or awkward landing with pain and swelling. A pop, rapid swelling within a few hours, and the knee feeling loose or giving way point more towards a significant tear, but the overlap is large. A clinician examines how the knee moves and how stable it is, and an MRI scan is used when a clearer look is needed. An X-ray shows bone, not the ligament.
What are the symptoms of a sprained ACL?
Typically pain in the knee after a twist or awkward landing, swelling over the following hours, stiffness, and the knee feeling less trustworthy than normal, especially when turning or going down stairs. With a mild sprain the knee still feels fundamentally stable. If it gives way, swells a lot very quickly, locks, or you can't put weight through it, get it assessed promptly.
What exercises help an ACL tear without surgery?
The aim is to make the muscles around the knee do more of the stabilising. AAOS says progressive physical therapy can restore the knee close to its pre-injury condition. That usually starts with getting the knee straight and switching the quadriceps back on, then builds to strengthening the quadriceps, hamstrings and hips, balance and single-leg control, and finally controlled jogging and change of direction. A physio sets the exact exercises and progression for your knee.
Sources
- ACL Injury: Does It Require Surgery?, AAOS OrthoInfo
- Anterior Cruciate Ligament (ACL) Injuries, AAOS OrthoInfo
- Alternatives to ACL (anterior cruciate ligament) surgery, NHS